Pediatric cardiology for the primary care pediatrician
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《美国医学杂志》
Division of Pediatric Cardiology, Department of Pediatrics, University of Texas Houston Medical School, Memorial Hermann Childrens Hospital, Houston, USA
Occurring at a rate of approximately 8 per thousand live births,[1] congenital cardiac defects are the most common forms of human malformation. With the current advances in pediatric cardiac surgery and percutaenous cardiac interventional procedures, more and more infants and children will survive and reach adulthood. It is estimated that the number of such patients will grow at a rate of 5% per year. [2] There is thus a very high likelihood that many primary care pediatricians (PCP) will encounter and be called upon to take care of this growing patient population.
The objectives of this article is to identify the different congenital heart defects (CHD) a PCP may encounter, as well as illustrate the natural and "unnatural" history of these defects. This article also aims to enable the pediatrician to anticipate and recognize problems commonly encountered in patients with CHD, so that timely consultations with a pediatric cardiologist may be sought.
The topics that will be discussed in this article include: (a) cardiac defects that may survive into adolescence or early adulthood without intervention; (b) cardiac defects diagnosed in infancy or childhood requiring early intervention; (c) anticipated problems of the former cardiac surgical patient; (d) general guidelines for the care of the child with congenital heart defects; and (e) the role of the PCP in the management of these patients, with emphasis on the team approach of collaborative management.
Cardiac Defects that May Survive into Adolescence or Early Adulthood Without Intervention
Certain heart defects, if mild and not hemodynamically significant, do not require medical or surgical intervention. Included among these are tiny patent foramen ovales, mild pulmonary stenosis, small, clinically silent patent ductus arteriosus, functionally normal (minimally stenotic or regurgitant) bicuspid aortic valves and small ventricular septal defects.[3] Other defects, such as mild Coarctation of the Aorta, may initially be well-tolerated, so that survival into early adulthood without intervention is possible. However, these patients may become symptomatic over time and require intervention then.
Atrial septal defects may be of the secundum, primuum or sinus venosus type. The first has the same embryologic origin as a patent foramen ovale and thus, if found in infancy, may spontaneously close during the first two years. If it fails to do so and remains to be of significant size, then elective closure may be recommended. The two latter types almost always require intervention. Many atrial septal defects are unrecognized for years because the patients are asymptomatic and cardiac physical examination findings may be quite subtle. Moderate to large defects must be closed to avoid long term complications such as pulmonary hypertension , atrial arrhythmias and right ventricular failure. Because right to left shunting may occur intermittently, paradoxical emboli resulting in stroke is a risk, even in small defects. With a history of stroke, intervention is warranted to prevent future catastrophic events.
When mild, valvar pulmonary stenosis tends to remain so. In a small subset of patients, stenosis may be progressive, typically during times of increased growth , such as during the first year of life or adolescence. This may be due to the development of valve commissural fusion, secondary hypertrophic subpulmonary stenosis or progressive calcification of the dysplastic pulmonary valve, which may occur in adulthood. With the exception of neonatal critical pulmonic stenosis, survival into adulthood, even without intervention, is the rule, and many present with an asymptomatic heart murmur.
Depending on the size of the shunt, many patients with patent ductus arteriosus (PDA) are asymptomatic. Those with sizable left to right shunts may have symptoms of congestive heart failure, and if left untreated, they may develop pulmonary hypertension and Eisenmenger's syndrome with progressive cyanosis and right heart failure. Small, pressure restrictive PDA's carry a cumulative risk for infective endocarditis, but this susceptibility has not been established for clinically silent PDA's (with no audible heart murmur) detected incidentally by Doppler color flow interrogation.
A bisucpid aortic valve may remain functionally normal over a lifetime. It is not uncommon, however, for the cusps to undergo calcification with progressive obstruction or regurgitation, especially in the elderly. Although progression of stenosis or regurgitation is typically gradual, bicuspid aortic valves may be rendered acutely and severely incompetent by a bout of infective endocarditis, to which they are very susceptible. Rarely, the aortic root may develop cystic medial necrosis and acute aortic root dissection, akin to Marfan's syndrome.[4]
Depending on the severity , coarctation of the aorta may be symptomatic in early infancy, early childhood, adolescence or adulthood. The majority of patients who survive infancy reach adulthood, but more than three quarters of patients die by the 5th decade without intervention.[5] The presenting symptom in an older child or adolescent may be the incidental finding of right upper extremity hypertension or lower extremity claudication. It must be kept in mind, however, that the presentation, though rare, may be catastrophic aortic aneurysm dissection or fatal cerebral hemorrhage from an associated cerebral berry aneurysm of the circle of Willis. Obtaining blood pressure measurements and palpation of both femoral pulses should thus be part of the routine pediatric physical examination, to screen for the presence of coarctation .
Isolated Ventricular septal defects (VSD) may be perimembranous, muscular, supracristal (subarterial) or inlet (AV canal) type. Spontaneous closure is a feature of the first two, and many do so within the first year of life. At least 5-10% of moderately large to non-restrictive defects may also close spontaneously. Older patients who survive without intervention fall into two categories: (1) those whose defects have closed spontaneously or have grown small enough to be hemodynamically inconsequential and (2) those with large VSDs who develop Eisenmenger's syndrome (irreversibly elevated pulmonary vascular resistance, with shunt reversal). Other than lung transplantation, the latter condition has no hope for cure and leads to progressive cyanosis, clinical deterioration and death. All VSDs are susceptible to endocarditis. The perimembranous and supracristal types may also be complicated by aortic valve leaflet prolapse through the defect, resulting in aortic regurgitation. When prolapse occurs, surgical intervention is recommended to avoid further aortic valve damage.
Patients with large left to right shunts (secondary to large VSDs, AV Canal defects or large PDAs) tend to develop symptoms of pulmonary overcirculation and congestive heart failure shortly after 6 to 12 weeks of life, when the normally elevated pulmonary vascular resistance of the newborn reaches its nadir. Clinical symptoms include tachycardia, tachypnea, poor feeding, failure to thrive, excessive diaphoresis and cardio-hepatomegaly. The medical management regimen includes digitalization, diuresis and caloric supplementation. The decision and timing for surgical intervention depends on the presence of complications or symptoms.
[TAG:2]Cardiac Defects Diagnosed in Infancy or Childhood Requiring Early Intervention[/TAG:2]
Some cardiac defects will result in certain death early in life if left untreated.
Intervention, of course, will alter their natural history. With improvements in myocardial preservation, surgical techniques and post-operative care, many of these patients survive into adulthood.
Tetralogy of Fallot (TOF) was originally described as the spectrum of a large mal-aligned VSD, with over-riding of the aorta, pulmonary outflow obstruction due to anterior deviation of the outlet septum, and right ventricular hypertrophy. The degree of cyanosis is determined by the severity of right heart obstruction, which may range from mild pulmonary stenosis to atresia of the pulmonary trunk. When obstruction to the right ventricular outflow tract (RVOT) is mild, cyanosis is minimal or even non-existent, the so-called "pink tets". The other extreme, pulmonary atresia, results in severe cyanosis once the PDA closes, in the absence of significant aorto-pulmonary artery collateral vessels.
The degree of RVOT obstruction may be dynamic. When a child with TOF is agitated or dehydrated, tachycardia and cardiac hypercontractility will result in hyperdynamic RVOT obstruction so that right to left shunting occurs at the ventricular level and the patient becomes profoundly cyanotic. This is commonly referred to a TET spell.
When this occurs, it is essential to comfort the child and minimize agitation, in the hopes of attenuating the tachycardia and hypercontractility that resulted in dynamic RVOT obstruction in the first place. Subcutaenous morphine accomplishes the same goal by sedating the child and diminishing hyperpnea. Placing the child in a knee chest position or giving a fluid bolus , tends to increase systemic venous return and right ventricular end diastolic volumes, both of which will force blood through the pulmonary circulation. Propranolol acts through its negative inotropic and chronotropic effects. Because shunting is intracardiac, supplemental 02 will not make a difference, and may make matters worse if it aggravates the child. If the above measures do not improve the cyanosis, intravenous phenylephrine, by virtue of increasing systemic vascular resistance, will decrese right to left shunting across the VSD and improve pulmonary blood flow. When all else fails, deep sedation or general anesthesia along with surgical intervention will be the only recourse.
In TOF, the degree of pulmonary stenosis tends to be progressive over time, even if it is mild initially. For this reason, surgery will eventually be required in all cases. Depending on the circumstances and associated problems, neonatal palliation with a systemic to pulmonary artery shunt, followed by complete intracardiac repair within the first year of life or early complete neonatal repair may be performed.
Years after repair of TOF, the left ventricular function is usually normal, except in rare cases that have had long standing volume overload, cyanosis, residual VSDs, or unrecognized coronary insufficiency. RV dysfunction and arrhythmias may occur[6] in patients who have had large RV outflow tract patches or residual pulmonary stenosis or insufficiency. Needless to say, patient who have undergone repair of TOF need to be followed by a cardiologist for life to determine if any of these complications will occur.[7]
D-Transposition of the great arteries (d-TGA) is a parallel circulation where systemic venous return goes through the right heart and out the aorta without ever reaching the lungs for oxygenation. Oxygenated pulmonary venous return, on the other hand, circulates through the left heart and out the pulmonary artery to return to the lungs without ever passing the body. In order to survive, there has to be some form of communication between the right and left circulations, either at the atrial, ventricular or great vessel level. If untreated, d-TGA results in a greater than 90% mortality in early infancy, and a 100% mortality later on.
With the advent of fetal echocardiography, it is fortunate that most cases of transposition are diagnosed in utero, and the old scenario of the cyanotic, acidotic newborn presenting to the emergency room during the first week of life after having been discharged from the nursery as a so-called "well-baby" is now more unusual. The goals of initial stabilization are the same: maintenance of normothermia., correction of acidocis, and fluid and electrolyte imbalances, along with judicious use of inotropes and diuretics as necessary. Prostaglandin is given intravenously to ensure ductal patency. But if this is not adequate to relieve cyanosis, a balloon atrial septostomy is performed to ensure intra-cardiac mixing, followed by an early arterial switch operation.
The arterial switch operation (ASO) is now the procedure of choice for neonates with d-TGA.[8] It involves "switching" the transposed arterial trunks along with coronary artery re-implantation early in the neonatal period. The 10-year-long term follow-up for the arterial switch operation is good.[9] In recent years, the peri-operative mortality is almost zero for uncomplicated cases.[10] However, survivors of the Switch need to be monitored for the development of RV or LV obstruction, pulmonary stenosis, neo-aortic insufficiency,[11] or coronary arterial complications. Morbidity is dominated by pulmonary stenosis and coronary abnormalities, with the potential for lethal arrhythmias.
Discussing the different forms of the Single ventricle and its nuances are beyond the scope of this paper. If one were to think of it simplistically, no matter which ventricle is hypoplastic, the patients' symptoms would depend on whether there is pulmonary or systemic outflow tract obstruction. For example, in tricuspid atresia with a hypoplastic right ventricle, normally related great vessels and pulmonary atresia, the patient would be cyanotic as a neonate and would be dependent on the patency of the ductus arteriosus for pulmonary blood flow. On the other hand, mitral atreisa, with a hypoplastic left ventricle and aortic atresia would result in systemic outflow obstruction. As a neonate, the patient would be dependent on the patency of the ductus arteriosus for systemic blood flow.
The initial physiology in all forms of single ventricle would be intracardiac mixing of oxygenated and de-oxygenated blood. Therefore saturations in the mid 70's to 80's are physiologic in these patients. Higher saturations achieved with over zealous oxygenation or mechanical ventilation is actually detrimental to their physiology. The ultimate goal of surgical palliation would be separation of the systemic and pulmonary circulations.
In the neonatal period, the objective is to relieve the patients' ductal dependence for pulmonary or systemic circulation. For the hypoplastic left heart syndrome, this may be achieved by the Norwood procedure, one of the components of which includes aortic arch reconstruction to relieve systemic blood flow obstruction. For the hypoplastic right ventricle with pulmonary blood flow obstruction, a systemic to pulmonary arterial shunt is in order. In complex cases with neither aortic nor pulmonary obstruction, preventing the development of congestive heart failure or pulmonary over-circulation with placement of a pulmonary arterial band may be the initial palliative procedure.
In later infancy, the goal of therapy would be to relieve defects that would impede the success of total cavo-pulmonary anastomosis later on. This includes relief of subaortic and pulmonary stenosis, if present. It is during this time that a Superior vena cava to pulmonary anastomosis (Glenn shunt) is undertaken.
In early childhood, complete separation of the systemic and pulmonary circulations with a total cavo-pulmonary anastomosis is the goal of therapy. Surgical palliation for the single ventricle, commonly known as the Fontan procedure, is based on the theory that the pulmonary vascular resistance in the mature lung is low enough that right atrial pressure can propel blood through the lungs, without the need for a sub-pulmonic ventricle. In order to achieve this, these patients should have a pulmonary anatomy free of distortion, with normal pulmonary arterial pressures and resistance. The presence of sinus rhythm, with competent valves and good single ventricle function are also important.
Short of heart transplantation, the Fontan operation is the only hope for the patient with a single ventricle, but one must remember that this is a palliative, and not a curative, procedure.[12] Long term complications that may arise over time include heart failure, thrombosis, intractable arrhythmias, protein losing enteropathy, and the so-called "weeping heart syndrome" consisting of pericardial and pleural effusions, ascites and peripheral edema. When irreversible hart failure occurs, cardiac transplantation may be the patient's only recourse.
Anticipated Problems of the Former Cardiac Surgical Patient
Although surgical outcomes for repair or palliation of congenital heart disease have improved dramatically over the past few years, many patients continue to have residual anatomic or physiologic derangements. It is imperative that the PCP be aware of these potential problems so that they may be anticipated and recognized during routine "well-child" visits.
Physical Examination Findings
Height and weight measurements that indicate improvement in growth velocity after cardiac intervention should be documented. The heart and respiratory rates, blood pressure recordings and presence of cyanosis should be carefully evaluated as well.
Heart murmurs are often present in post-operative patients and are not necessarily pathologic. A review of the discharge summary and the post-operative echocardiographic report will indicate residual lesions known to be present upon discharge from the hospital. Soft flow murmurs are often heard after a VSD or ASD repair from blood flow turbulence. Louder (more than grade 2-3/6) murmurs may suggest the presence of residual lesions. Continuous murmurs should be auscultated in surgically placed systemic to pulmonary arterial shunts or native aorto-pulmonary collaterals. A metallic snap is expected in patients with valvar prosthesis and its absence, when it was previously auscultated, is a cause for concern. Muffled, distant heart sounds may suggest the presence of post-pericardiotomy syndrome resulting in a pericardial effusion. This may occur several days or weeks after open heart surgery. Tachycardia, decreased pulse pressure and evidence for decreased cardiac output may also be evident and require urgent intervention.
Decreased breath sounds may indicate the presence of pleural effusions following a Fontan operation. Four extremity blood pressure differentials and diminished lower extremity pulses may alert the PCP to the presence of recoarctation of the aorta. The operative incision and sites of line placement should be examined closely for evidence of infection. The liver dimensions should also be compared to previous evaluations.
Laboratory and Ancillary Studies
All laboratory tests should be dictated by clinical indications. Post-operative patients or those with cyanosis and polycythemia will need complete blood counts as they may be prone to develop iron deficiency anemia and require iron supplementation. Those on chronic diuretic therapy or electrolyte supplementation will require periodic serum electrolyte evaluations. Patients with mechanical prosthetic valves on Warfarin should have regular INR (international normalized ratio) monitoring, with a goal of 2.5 to 3.5 to prevent hemorrhagic events and thrombo-embolism.[13]
To avoid repetition of tests by multiple caregivers, electrocardiograms, holters, echocardiograms and stress tests are best ordered in collaboration with a pediatric cardiologist. These tests should be undertaken with precise questions in mind, focusing on the patient's particular heart condition and unique pathophysiologic characteristics.
Endocarditis Risk
Save for ASDs, the large majority of patients with congenital heart defects are susceptible to endocarditis. In this condition, normal flora, or sometimes more virulent pathogens, invade the blood stream and lodge onto abnormal cardiac tissues or valves. Cardiac lesions resulting in turbulent blood flow such as small, pressure restrictive VSD's, surgically created systemic to pulmonary arterial shunts, complex cyanotic cardiac lesions, and prosthetic heart valves are at highest risk. Because the most common source of bacteremia is from an occult oral infection, strict dental hygiene and regular bi-annual dental visits are recommended for these patients. The American Heart Association has published guidelines for endocarditis prophylaxis[14] , outlining the low and high risk procedures and the antibiotic regimen recommended for them.
Sudden Cardiac Death
Sudden cardiac death in the young is rare, estimated to be between 1.1-2 per 200,000 persons per year.[15] ,[16] The risk is higher in patients with congenital cardiac defects, especially those associated with increased ventricular pressure (Severe aortic or pulmonary stenosis and hypertrophic cardiomyopathy) or coronary arterial abnormalities, where the risk is estimated to be as high as 5 per thousand persons per year.[17] Although only a minority had documented ventricular tachycardia, many had ventricular dysfunction, a known risk factor for ventricular arrhythmias. It is thus important that the PCP be vigilant in anticipating this potentially devastating event in the patient with known cardiac disease. Soliciting information regarding palpitations, syncope or near syncope and paying particular attention to irregularities in the heart rate or rhythm, should be part of every "well-child" visit.
General Guidelines for the Care of the Child with Congenital Heart Defects
The following are general "housekeeping" guidelines I would suggest to Primary Care pediatricians who are taking care of children with congenital cardiac defects.
When confronted with a fetus or newborn with CHD, one must always try to look for other associated anomalies, as there are some forms of heart defects that exist as part of syndrome complexes. For example, the cono-truncal defects TOF and d-TGA may be associated with other midline defects such as cleft lip and palate and diGeorge syndrome. Some associated anomalies such as imperforate anus, duodenal atresia or diaphragmatic hernia may require medical and surgical attention first.
One must also keep in mind that long standing cyanosis results in polycythemia and a relative iron deficiency. There is evidence suggesting that iron deficient cyanotic children are prone to develop blood sludging, which increases their risk for neuro-cerebral complications.[18] Furthermore, children with cyanosis due to right to left shunts are at risk for paradoxical emboli and stroke.
It must also be remembered that some relatively insidious and benign illnesses, such as acute gastro-enteritis or a respiratory viral syndrome, which would otherwise be well tolerated by a normal child, could have devastating effects on a child with a single ventricle, as they are very dependent on their intravascular volume and may have very little cardiac reserve. Even a "pink TET" would spell if he becomes dehydrated. Children who have undergone heart surgery, even for a lesion as benign as an atrial septal defect, may develop arrhythmias requiring therapy. Complaints of palpitations or chest pain may not be too benign after all.
Over time, even children who appear to be adequately repaired or palliated may develop recurrent lesions, such as recurrent coarctation, or subaortic or subpulmonic stenoses. Prosthetic valves are thrombogenic, necessitating anti-coagulation for life. They also have limited durability and may be outgrown. Conduits and prosthetic patch materials may calcify, dehisce, form aneurysms or become obstructed. The presence of a new onset murmur may alert one to the development of this. Chronic volume overload or cyanosis may take its toll on the heart and result in the development of ventricular dysfunction.
The American Academy of Pediatrics recommends the Hemophilus influenza b (Hib) series[19] and the pneumococcal vaccine[20] for all children as part of routine immunizations. However, patients with heterotaxy and asplenia also need antibiotic asplenia prohylaxis with penicillin, amoxicillin or erythromycin.[21]
Recently, Synagis or Palivizumab has been utilized for children less than two years of age,[22] with hemodynamically significant CHD, CHF or cyanosis, for prohylaxis against the respiratory syncitial virus (RSV).[23] This humanized mouse monoclonal antibody against RSV is given at a dose of 15 mg/kg IM every month for 5 months during RSV season. Yearly influenza vaccination is also encouraged.[24] , [25]
One must also keep in mind that children with hemodynamically significant heart defects may develop failure to thrive and growth retardation from diminished intake and increased caloric needs. Caloric supplementation, sometimes with NG feedings at night, may be necessary until the heart defects are surgically corrected or even post-operatively. One must set reasonable expectations for growth and be cognizant of the fact that developmental, social, intellectual and neurologic delay is a reality in many of these patients. As a caring PCP, one must refer the patient and family to the appropriate agency for speech, occupational or nutritional therapy. Also, one must encourage sports and athletic participation to the extent allowed by their cardiac defect. This determination may be made in conjunction with the child's pediatric cardiologist.
The Role of the PCP in the Management of the Child With CHD
The role of the PCP in the management of the child with congenital cardiac defects cannot be over emphasized. Management ideally should be a collaborative team approach. Just as the PCP relies on the pediatric cardiologist to take care of many cardiac issues, the pediatric cardiologist in turn also heavily relies on the PCP to take care of the numerous general problems these patients encounter. Medical or surgical cardiac interventions may be recommended at a time when the patient is still asymptomatic, based on our knowledge of the natural history of the disease process. The pediatric cardiologist thus relies on the PCP to help stress this fact to the family and ensure that the patient receives regular cardiac follow-up. Indeed, our shared goal in caring for our mutual patients is to help them improve the quality and quantity of their lives.
References
1. Fyler DC. Prevalence. In Nadas' Pediatric Cardiology , by Fyler DC, ed. Philadelphia, Mosby-Year Book, Inc., 1992; 273.
2. Kaplan S. Natural and Post-operative history across age groups. Cardiol Clin 1993; 11(4): 543-546.
3. Hannoush H, Tamim H, Younes H, Arnaout S, Gharzeddine W, Dakik H et al. Patterns of congenital heart disease in unoperated adults: a 20-year experience in a developing country. Clin Cardiol 2004; 27(4): 236-240.
4. Roberts CS, Roberts WC. Dissection of the Aorta associated with congenital malformation of the aortic valve. J Am Coll Cardiol 1991; 17: 712.
5. Perloff JK. Coarctation of the Aorta, In The Clinical Recognition of Congenital heart Disease. Philadelphia, W.B. Saunders Company, 1994; 132.
6. D'Andrea A, Caso P, Sarubbi B, Russo MG, Ascione L, Scherillo M et al. Right ventricular myocardial dysfunction in adult patients late after repair of tetralogy of fallot. Int J Cardiol 2004; 94(2-3): 213-220.
7. Geva T, Sandweiss BM, Gauvreau K, Lock JE, Powell AJ. Factors associated with impaired clinical status in long-term survivors of tetralogy of Fallot repair evaluated by magnetic resonance imaging. J Am Coll Cardiol 2004; 43(6): 1068-1074.
8. Duncan BW, Poirier NC, Mee RB, Drummond-Webb JJ, Qureshi A, Mesia CI et al. Selective timing for the arterial switch operation. Ann Thorac Surg 2004; 77(5): 1691-1696.
9. Hovels-Gurich HH, Seghaye MC, Ma Q, Miskova M, Minkenberg R et al. Long-term results of cardiac and general health status in children after neonatal arterial switch operation. Ann Thorac Surg 2003; 75(3): 935-943.
10. Dibardino DJ, Allison AE, Vaughn WK, McKenzie ED, Fraser CD Jr. Current expectations for newborns undergoing the arterial switch operation. Ann Surg 2004; 239(5): 588-596; discussion 596-598.
11. Formigari R, Toscano A, Giardini A, Gargiulo G, Di Donato R, Picchio FM et al. Prevalence and predictors of neoaortic regurgitation after arterial switch operation for transposition of the great arteries. J Thorac Cardiovasc Surg 2003; 126(6): 1753-1759.
12. Van den Bosch AE, Roos-Hesselink JW, Van Domburg R, Bogers AJ, Simoons ML, Meijboom FJ. Long-term outcome and quality of life in adult patients after the Fontan operation. Am J Cardiol 2004; 93(9): 1141-1145.
13. Vink R, Van Den Brink RB, Levi M. Management of anticoagulant therapy for patients with prosthetic heart valves or atrial fibrillation. Hematology 2004; 9(1): 1-9.
14. Committee on Rheumatic Fever and Bacterial Endocarditis of the Council on Cardiovascular Diseases in the Young, American Academy of Pediatrics. Prevention of bacterial endocarditis. Pediatrics 1985; 75(3): 603-607.
15. Wever EF, Robles de Medina EO. Sudden death in patients without structural heart disease. J Am Coll Cardiol 2004; 7;43(7): 1137-1144.
16. Harrison D, Connely M, Harris L el al. Sudden cardiac death in the adult with congenital heart disease. Can J Cardiol 1996;12: 1161-1163.
17. Firoozi S, Sharma S, McKenna WJ: Risk of competitive sport in young athletes with heart disease. Heart 2003; 89: 710-714.
18. Yager JY, Hartfield DS. Neurologic manifestations of iron deficiency in childhood. Pediatr Neurol 2002; 27(2): 85-92.
19. Centers for Disease Control and Prevention (CDC). Recommended childhood and adolescent immunization schedule-United States, January-June 2004. MMWR Morb Mortal Wkly Rep 2004; 16; 53(1): Q1-4.
20. Advisory Committee on Immunization Practices. Preventing pneumococcal disease among infants and young children. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 2000; 49(RR-9): 1-35.
21. Schutze GE, Mason EO Jr, Barson WJ, Kim KS, Wald ER, Givner LB et al. Invasive pneumococcal infections in children with asplenia. Pediatr Infect Dis J 2002; 21(4): 278-282.
22. Tulloh R, Marsh M, Blackburn M, Casey F, Lenney W, Weller P et al. Working Group of the British Paediatric Cardiac Association. Recommendations for the use of palivizumab as prophylaxis against respiratory syncytial virus in infants with congenital cardiac disease. Cardiol Young 2003; 13(5): 420-423.
23. Cabalka AK. Physiologic risk factors for respiratory viral infections and immunoprophylaxis for respiratory syncytial virus in young children with congenital heart disease. Pediatr Infect Dis J 2004; 23(1 Suppl): S41-45.
24. Ruben FL. Inactivated influenza virus vaccines in children. Clin Infect Dis 2004; 38(5): 678-688.
25. Neuzil KM, Wright PF, Mitchel EF Jr, Griffin MR. The burden of influenza illness in children with asthma and other chronic medical conditions. J Pediatr 2000; 2000; 137(6): 856-864.(Lantin-Hermoso M Regina)
Occurring at a rate of approximately 8 per thousand live births,[1] congenital cardiac defects are the most common forms of human malformation. With the current advances in pediatric cardiac surgery and percutaenous cardiac interventional procedures, more and more infants and children will survive and reach adulthood. It is estimated that the number of such patients will grow at a rate of 5% per year. [2] There is thus a very high likelihood that many primary care pediatricians (PCP) will encounter and be called upon to take care of this growing patient population.
The objectives of this article is to identify the different congenital heart defects (CHD) a PCP may encounter, as well as illustrate the natural and "unnatural" history of these defects. This article also aims to enable the pediatrician to anticipate and recognize problems commonly encountered in patients with CHD, so that timely consultations with a pediatric cardiologist may be sought.
The topics that will be discussed in this article include: (a) cardiac defects that may survive into adolescence or early adulthood without intervention; (b) cardiac defects diagnosed in infancy or childhood requiring early intervention; (c) anticipated problems of the former cardiac surgical patient; (d) general guidelines for the care of the child with congenital heart defects; and (e) the role of the PCP in the management of these patients, with emphasis on the team approach of collaborative management.
Cardiac Defects that May Survive into Adolescence or Early Adulthood Without Intervention
Certain heart defects, if mild and not hemodynamically significant, do not require medical or surgical intervention. Included among these are tiny patent foramen ovales, mild pulmonary stenosis, small, clinically silent patent ductus arteriosus, functionally normal (minimally stenotic or regurgitant) bicuspid aortic valves and small ventricular septal defects.[3] Other defects, such as mild Coarctation of the Aorta, may initially be well-tolerated, so that survival into early adulthood without intervention is possible. However, these patients may become symptomatic over time and require intervention then.
Atrial septal defects may be of the secundum, primuum or sinus venosus type. The first has the same embryologic origin as a patent foramen ovale and thus, if found in infancy, may spontaneously close during the first two years. If it fails to do so and remains to be of significant size, then elective closure may be recommended. The two latter types almost always require intervention. Many atrial septal defects are unrecognized for years because the patients are asymptomatic and cardiac physical examination findings may be quite subtle. Moderate to large defects must be closed to avoid long term complications such as pulmonary hypertension , atrial arrhythmias and right ventricular failure. Because right to left shunting may occur intermittently, paradoxical emboli resulting in stroke is a risk, even in small defects. With a history of stroke, intervention is warranted to prevent future catastrophic events.
When mild, valvar pulmonary stenosis tends to remain so. In a small subset of patients, stenosis may be progressive, typically during times of increased growth , such as during the first year of life or adolescence. This may be due to the development of valve commissural fusion, secondary hypertrophic subpulmonary stenosis or progressive calcification of the dysplastic pulmonary valve, which may occur in adulthood. With the exception of neonatal critical pulmonic stenosis, survival into adulthood, even without intervention, is the rule, and many present with an asymptomatic heart murmur.
Depending on the size of the shunt, many patients with patent ductus arteriosus (PDA) are asymptomatic. Those with sizable left to right shunts may have symptoms of congestive heart failure, and if left untreated, they may develop pulmonary hypertension and Eisenmenger's syndrome with progressive cyanosis and right heart failure. Small, pressure restrictive PDA's carry a cumulative risk for infective endocarditis, but this susceptibility has not been established for clinically silent PDA's (with no audible heart murmur) detected incidentally by Doppler color flow interrogation.
A bisucpid aortic valve may remain functionally normal over a lifetime. It is not uncommon, however, for the cusps to undergo calcification with progressive obstruction or regurgitation, especially in the elderly. Although progression of stenosis or regurgitation is typically gradual, bicuspid aortic valves may be rendered acutely and severely incompetent by a bout of infective endocarditis, to which they are very susceptible. Rarely, the aortic root may develop cystic medial necrosis and acute aortic root dissection, akin to Marfan's syndrome.[4]
Depending on the severity , coarctation of the aorta may be symptomatic in early infancy, early childhood, adolescence or adulthood. The majority of patients who survive infancy reach adulthood, but more than three quarters of patients die by the 5th decade without intervention.[5] The presenting symptom in an older child or adolescent may be the incidental finding of right upper extremity hypertension or lower extremity claudication. It must be kept in mind, however, that the presentation, though rare, may be catastrophic aortic aneurysm dissection or fatal cerebral hemorrhage from an associated cerebral berry aneurysm of the circle of Willis. Obtaining blood pressure measurements and palpation of both femoral pulses should thus be part of the routine pediatric physical examination, to screen for the presence of coarctation .
Isolated Ventricular septal defects (VSD) may be perimembranous, muscular, supracristal (subarterial) or inlet (AV canal) type. Spontaneous closure is a feature of the first two, and many do so within the first year of life. At least 5-10% of moderately large to non-restrictive defects may also close spontaneously. Older patients who survive without intervention fall into two categories: (1) those whose defects have closed spontaneously or have grown small enough to be hemodynamically inconsequential and (2) those with large VSDs who develop Eisenmenger's syndrome (irreversibly elevated pulmonary vascular resistance, with shunt reversal). Other than lung transplantation, the latter condition has no hope for cure and leads to progressive cyanosis, clinical deterioration and death. All VSDs are susceptible to endocarditis. The perimembranous and supracristal types may also be complicated by aortic valve leaflet prolapse through the defect, resulting in aortic regurgitation. When prolapse occurs, surgical intervention is recommended to avoid further aortic valve damage.
Patients with large left to right shunts (secondary to large VSDs, AV Canal defects or large PDAs) tend to develop symptoms of pulmonary overcirculation and congestive heart failure shortly after 6 to 12 weeks of life, when the normally elevated pulmonary vascular resistance of the newborn reaches its nadir. Clinical symptoms include tachycardia, tachypnea, poor feeding, failure to thrive, excessive diaphoresis and cardio-hepatomegaly. The medical management regimen includes digitalization, diuresis and caloric supplementation. The decision and timing for surgical intervention depends on the presence of complications or symptoms.
[TAG:2]Cardiac Defects Diagnosed in Infancy or Childhood Requiring Early Intervention[/TAG:2]
Some cardiac defects will result in certain death early in life if left untreated.
Intervention, of course, will alter their natural history. With improvements in myocardial preservation, surgical techniques and post-operative care, many of these patients survive into adulthood.
Tetralogy of Fallot (TOF) was originally described as the spectrum of a large mal-aligned VSD, with over-riding of the aorta, pulmonary outflow obstruction due to anterior deviation of the outlet septum, and right ventricular hypertrophy. The degree of cyanosis is determined by the severity of right heart obstruction, which may range from mild pulmonary stenosis to atresia of the pulmonary trunk. When obstruction to the right ventricular outflow tract (RVOT) is mild, cyanosis is minimal or even non-existent, the so-called "pink tets". The other extreme, pulmonary atresia, results in severe cyanosis once the PDA closes, in the absence of significant aorto-pulmonary artery collateral vessels.
The degree of RVOT obstruction may be dynamic. When a child with TOF is agitated or dehydrated, tachycardia and cardiac hypercontractility will result in hyperdynamic RVOT obstruction so that right to left shunting occurs at the ventricular level and the patient becomes profoundly cyanotic. This is commonly referred to a TET spell.
When this occurs, it is essential to comfort the child and minimize agitation, in the hopes of attenuating the tachycardia and hypercontractility that resulted in dynamic RVOT obstruction in the first place. Subcutaenous morphine accomplishes the same goal by sedating the child and diminishing hyperpnea. Placing the child in a knee chest position or giving a fluid bolus , tends to increase systemic venous return and right ventricular end diastolic volumes, both of which will force blood through the pulmonary circulation. Propranolol acts through its negative inotropic and chronotropic effects. Because shunting is intracardiac, supplemental 02 will not make a difference, and may make matters worse if it aggravates the child. If the above measures do not improve the cyanosis, intravenous phenylephrine, by virtue of increasing systemic vascular resistance, will decrese right to left shunting across the VSD and improve pulmonary blood flow. When all else fails, deep sedation or general anesthesia along with surgical intervention will be the only recourse.
In TOF, the degree of pulmonary stenosis tends to be progressive over time, even if it is mild initially. For this reason, surgery will eventually be required in all cases. Depending on the circumstances and associated problems, neonatal palliation with a systemic to pulmonary artery shunt, followed by complete intracardiac repair within the first year of life or early complete neonatal repair may be performed.
Years after repair of TOF, the left ventricular function is usually normal, except in rare cases that have had long standing volume overload, cyanosis, residual VSDs, or unrecognized coronary insufficiency. RV dysfunction and arrhythmias may occur[6] in patients who have had large RV outflow tract patches or residual pulmonary stenosis or insufficiency. Needless to say, patient who have undergone repair of TOF need to be followed by a cardiologist for life to determine if any of these complications will occur.[7]
D-Transposition of the great arteries (d-TGA) is a parallel circulation where systemic venous return goes through the right heart and out the aorta without ever reaching the lungs for oxygenation. Oxygenated pulmonary venous return, on the other hand, circulates through the left heart and out the pulmonary artery to return to the lungs without ever passing the body. In order to survive, there has to be some form of communication between the right and left circulations, either at the atrial, ventricular or great vessel level. If untreated, d-TGA results in a greater than 90% mortality in early infancy, and a 100% mortality later on.
With the advent of fetal echocardiography, it is fortunate that most cases of transposition are diagnosed in utero, and the old scenario of the cyanotic, acidotic newborn presenting to the emergency room during the first week of life after having been discharged from the nursery as a so-called "well-baby" is now more unusual. The goals of initial stabilization are the same: maintenance of normothermia., correction of acidocis, and fluid and electrolyte imbalances, along with judicious use of inotropes and diuretics as necessary. Prostaglandin is given intravenously to ensure ductal patency. But if this is not adequate to relieve cyanosis, a balloon atrial septostomy is performed to ensure intra-cardiac mixing, followed by an early arterial switch operation.
The arterial switch operation (ASO) is now the procedure of choice for neonates with d-TGA.[8] It involves "switching" the transposed arterial trunks along with coronary artery re-implantation early in the neonatal period. The 10-year-long term follow-up for the arterial switch operation is good.[9] In recent years, the peri-operative mortality is almost zero for uncomplicated cases.[10] However, survivors of the Switch need to be monitored for the development of RV or LV obstruction, pulmonary stenosis, neo-aortic insufficiency,[11] or coronary arterial complications. Morbidity is dominated by pulmonary stenosis and coronary abnormalities, with the potential for lethal arrhythmias.
Discussing the different forms of the Single ventricle and its nuances are beyond the scope of this paper. If one were to think of it simplistically, no matter which ventricle is hypoplastic, the patients' symptoms would depend on whether there is pulmonary or systemic outflow tract obstruction. For example, in tricuspid atresia with a hypoplastic right ventricle, normally related great vessels and pulmonary atresia, the patient would be cyanotic as a neonate and would be dependent on the patency of the ductus arteriosus for pulmonary blood flow. On the other hand, mitral atreisa, with a hypoplastic left ventricle and aortic atresia would result in systemic outflow obstruction. As a neonate, the patient would be dependent on the patency of the ductus arteriosus for systemic blood flow.
The initial physiology in all forms of single ventricle would be intracardiac mixing of oxygenated and de-oxygenated blood. Therefore saturations in the mid 70's to 80's are physiologic in these patients. Higher saturations achieved with over zealous oxygenation or mechanical ventilation is actually detrimental to their physiology. The ultimate goal of surgical palliation would be separation of the systemic and pulmonary circulations.
In the neonatal period, the objective is to relieve the patients' ductal dependence for pulmonary or systemic circulation. For the hypoplastic left heart syndrome, this may be achieved by the Norwood procedure, one of the components of which includes aortic arch reconstruction to relieve systemic blood flow obstruction. For the hypoplastic right ventricle with pulmonary blood flow obstruction, a systemic to pulmonary arterial shunt is in order. In complex cases with neither aortic nor pulmonary obstruction, preventing the development of congestive heart failure or pulmonary over-circulation with placement of a pulmonary arterial band may be the initial palliative procedure.
In later infancy, the goal of therapy would be to relieve defects that would impede the success of total cavo-pulmonary anastomosis later on. This includes relief of subaortic and pulmonary stenosis, if present. It is during this time that a Superior vena cava to pulmonary anastomosis (Glenn shunt) is undertaken.
In early childhood, complete separation of the systemic and pulmonary circulations with a total cavo-pulmonary anastomosis is the goal of therapy. Surgical palliation for the single ventricle, commonly known as the Fontan procedure, is based on the theory that the pulmonary vascular resistance in the mature lung is low enough that right atrial pressure can propel blood through the lungs, without the need for a sub-pulmonic ventricle. In order to achieve this, these patients should have a pulmonary anatomy free of distortion, with normal pulmonary arterial pressures and resistance. The presence of sinus rhythm, with competent valves and good single ventricle function are also important.
Short of heart transplantation, the Fontan operation is the only hope for the patient with a single ventricle, but one must remember that this is a palliative, and not a curative, procedure.[12] Long term complications that may arise over time include heart failure, thrombosis, intractable arrhythmias, protein losing enteropathy, and the so-called "weeping heart syndrome" consisting of pericardial and pleural effusions, ascites and peripheral edema. When irreversible hart failure occurs, cardiac transplantation may be the patient's only recourse.
Anticipated Problems of the Former Cardiac Surgical Patient
Although surgical outcomes for repair or palliation of congenital heart disease have improved dramatically over the past few years, many patients continue to have residual anatomic or physiologic derangements. It is imperative that the PCP be aware of these potential problems so that they may be anticipated and recognized during routine "well-child" visits.
Physical Examination Findings
Height and weight measurements that indicate improvement in growth velocity after cardiac intervention should be documented. The heart and respiratory rates, blood pressure recordings and presence of cyanosis should be carefully evaluated as well.
Heart murmurs are often present in post-operative patients and are not necessarily pathologic. A review of the discharge summary and the post-operative echocardiographic report will indicate residual lesions known to be present upon discharge from the hospital. Soft flow murmurs are often heard after a VSD or ASD repair from blood flow turbulence. Louder (more than grade 2-3/6) murmurs may suggest the presence of residual lesions. Continuous murmurs should be auscultated in surgically placed systemic to pulmonary arterial shunts or native aorto-pulmonary collaterals. A metallic snap is expected in patients with valvar prosthesis and its absence, when it was previously auscultated, is a cause for concern. Muffled, distant heart sounds may suggest the presence of post-pericardiotomy syndrome resulting in a pericardial effusion. This may occur several days or weeks after open heart surgery. Tachycardia, decreased pulse pressure and evidence for decreased cardiac output may also be evident and require urgent intervention.
Decreased breath sounds may indicate the presence of pleural effusions following a Fontan operation. Four extremity blood pressure differentials and diminished lower extremity pulses may alert the PCP to the presence of recoarctation of the aorta. The operative incision and sites of line placement should be examined closely for evidence of infection. The liver dimensions should also be compared to previous evaluations.
Laboratory and Ancillary Studies
All laboratory tests should be dictated by clinical indications. Post-operative patients or those with cyanosis and polycythemia will need complete blood counts as they may be prone to develop iron deficiency anemia and require iron supplementation. Those on chronic diuretic therapy or electrolyte supplementation will require periodic serum electrolyte evaluations. Patients with mechanical prosthetic valves on Warfarin should have regular INR (international normalized ratio) monitoring, with a goal of 2.5 to 3.5 to prevent hemorrhagic events and thrombo-embolism.[13]
To avoid repetition of tests by multiple caregivers, electrocardiograms, holters, echocardiograms and stress tests are best ordered in collaboration with a pediatric cardiologist. These tests should be undertaken with precise questions in mind, focusing on the patient's particular heart condition and unique pathophysiologic characteristics.
Endocarditis Risk
Save for ASDs, the large majority of patients with congenital heart defects are susceptible to endocarditis. In this condition, normal flora, or sometimes more virulent pathogens, invade the blood stream and lodge onto abnormal cardiac tissues or valves. Cardiac lesions resulting in turbulent blood flow such as small, pressure restrictive VSD's, surgically created systemic to pulmonary arterial shunts, complex cyanotic cardiac lesions, and prosthetic heart valves are at highest risk. Because the most common source of bacteremia is from an occult oral infection, strict dental hygiene and regular bi-annual dental visits are recommended for these patients. The American Heart Association has published guidelines for endocarditis prophylaxis[14] , outlining the low and high risk procedures and the antibiotic regimen recommended for them.
Sudden Cardiac Death
Sudden cardiac death in the young is rare, estimated to be between 1.1-2 per 200,000 persons per year.[15] ,[16] The risk is higher in patients with congenital cardiac defects, especially those associated with increased ventricular pressure (Severe aortic or pulmonary stenosis and hypertrophic cardiomyopathy) or coronary arterial abnormalities, where the risk is estimated to be as high as 5 per thousand persons per year.[17] Although only a minority had documented ventricular tachycardia, many had ventricular dysfunction, a known risk factor for ventricular arrhythmias. It is thus important that the PCP be vigilant in anticipating this potentially devastating event in the patient with known cardiac disease. Soliciting information regarding palpitations, syncope or near syncope and paying particular attention to irregularities in the heart rate or rhythm, should be part of every "well-child" visit.
General Guidelines for the Care of the Child with Congenital Heart Defects
The following are general "housekeeping" guidelines I would suggest to Primary Care pediatricians who are taking care of children with congenital cardiac defects.
When confronted with a fetus or newborn with CHD, one must always try to look for other associated anomalies, as there are some forms of heart defects that exist as part of syndrome complexes. For example, the cono-truncal defects TOF and d-TGA may be associated with other midline defects such as cleft lip and palate and diGeorge syndrome. Some associated anomalies such as imperforate anus, duodenal atresia or diaphragmatic hernia may require medical and surgical attention first.
One must also keep in mind that long standing cyanosis results in polycythemia and a relative iron deficiency. There is evidence suggesting that iron deficient cyanotic children are prone to develop blood sludging, which increases their risk for neuro-cerebral complications.[18] Furthermore, children with cyanosis due to right to left shunts are at risk for paradoxical emboli and stroke.
It must also be remembered that some relatively insidious and benign illnesses, such as acute gastro-enteritis or a respiratory viral syndrome, which would otherwise be well tolerated by a normal child, could have devastating effects on a child with a single ventricle, as they are very dependent on their intravascular volume and may have very little cardiac reserve. Even a "pink TET" would spell if he becomes dehydrated. Children who have undergone heart surgery, even for a lesion as benign as an atrial septal defect, may develop arrhythmias requiring therapy. Complaints of palpitations or chest pain may not be too benign after all.
Over time, even children who appear to be adequately repaired or palliated may develop recurrent lesions, such as recurrent coarctation, or subaortic or subpulmonic stenoses. Prosthetic valves are thrombogenic, necessitating anti-coagulation for life. They also have limited durability and may be outgrown. Conduits and prosthetic patch materials may calcify, dehisce, form aneurysms or become obstructed. The presence of a new onset murmur may alert one to the development of this. Chronic volume overload or cyanosis may take its toll on the heart and result in the development of ventricular dysfunction.
The American Academy of Pediatrics recommends the Hemophilus influenza b (Hib) series[19] and the pneumococcal vaccine[20] for all children as part of routine immunizations. However, patients with heterotaxy and asplenia also need antibiotic asplenia prohylaxis with penicillin, amoxicillin or erythromycin.[21]
Recently, Synagis or Palivizumab has been utilized for children less than two years of age,[22] with hemodynamically significant CHD, CHF or cyanosis, for prohylaxis against the respiratory syncitial virus (RSV).[23] This humanized mouse monoclonal antibody against RSV is given at a dose of 15 mg/kg IM every month for 5 months during RSV season. Yearly influenza vaccination is also encouraged.[24] , [25]
One must also keep in mind that children with hemodynamically significant heart defects may develop failure to thrive and growth retardation from diminished intake and increased caloric needs. Caloric supplementation, sometimes with NG feedings at night, may be necessary until the heart defects are surgically corrected or even post-operatively. One must set reasonable expectations for growth and be cognizant of the fact that developmental, social, intellectual and neurologic delay is a reality in many of these patients. As a caring PCP, one must refer the patient and family to the appropriate agency for speech, occupational or nutritional therapy. Also, one must encourage sports and athletic participation to the extent allowed by their cardiac defect. This determination may be made in conjunction with the child's pediatric cardiologist.
The Role of the PCP in the Management of the Child With CHD
The role of the PCP in the management of the child with congenital cardiac defects cannot be over emphasized. Management ideally should be a collaborative team approach. Just as the PCP relies on the pediatric cardiologist to take care of many cardiac issues, the pediatric cardiologist in turn also heavily relies on the PCP to take care of the numerous general problems these patients encounter. Medical or surgical cardiac interventions may be recommended at a time when the patient is still asymptomatic, based on our knowledge of the natural history of the disease process. The pediatric cardiologist thus relies on the PCP to help stress this fact to the family and ensure that the patient receives regular cardiac follow-up. Indeed, our shared goal in caring for our mutual patients is to help them improve the quality and quantity of their lives.
References
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