Assessment of tricuspid valve annulus size, shape and function using real-time three-dimensional echocardiography
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《血管的通路杂志》
a Thoraxcenter, Room Ba 302, Erasmus MC, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands
b Cardiology Department, Al-Husein University Hospital, Al-Azhar University, Cairo, Egypt
Abstract
Tricuspid annulus (TA) evaluation continues to be a major problem in the surgical decision-making process. Obviously, 2-dimensional transthoracic echocardiography (2D TTE) is limited in TA visualization due to its complex 3D shape. The study aimed to determine TA morphology, size and function with real-time three-dimensional echocardiography (RT3DE) in 40 patients divided into two equal groups (I: normal TA and II: dilated). 2D TTE measurements included TA diameter (TAD) at apical 4-chamber (AP4CH) and parasternal short axis (PSAX) views. RT3DE measurements included TA area (TAA), major TAD and minor TAD. TA fractional shortening (TAFS), and TA fractional area change (TAFAC) were calculated from end-systolic and end-diastolic measurements. RT3DE allowed visualization and measurement of the entire oval-shaped TA in all patients irrespective of its size (normal or dilated). 2D TTE measurement of TAD at both AP4CH and at PSAX views was significantly smaller than the major TAD measured by RT3DE (P<0.0001) and nearly matched with the minor TAD in all patients. Calculation of TAFS was comparable with both techniques. TAFAC was significantly higher than TAFS (P<0.0001). So, RT3DE could be relied on more accurately than 2D TTE in the assessment of TA size and function which may aid in decision-making and selection of proper surgical procedure when indicated.
Key Words: Tricuspid annulus; Real-time 3D echocardiography
1. Introduction
The tricuspid valve (TV) is composed of three leaflets (anterior, posterior and septal) attached to a fibrous annulus [1]. The three-dimensional (3D) shape of this tricuspid annulus (TA) is complex and does not conform to a flat ring [2]. Tricuspid regurgitation (TR) is the most common pathology affecting the TV. An understanding of the pathological process underlying TR is necessary to determine the optimal management strategy. Usually, TR is secondary to left-sided valvular pathology (mostly mitral valve disease) with pulmonary hypertension and right ventricular dilatation [3,4]. Because the TA is a component of the right ventricle it will dilate also. However, since the septal leaflet is fixed between the fibrous trigones, the TA can only lengthen and dilate along the attachment of the anterior and posterior leaflets [5–7]. Unfortunately, TV evaluation continues to be a major problem in the surgical decision-making process [8]. Guidelines for TV repair include TA assessment (indexed TA size 2.1 cm/m2 and TA fractional shortening <25%) [3]. At the time of surgery the decision to repair the TV may be changed due to discrepant TA diameter (TAD) findings between pre-operative two-dimensional transthoracic (or transesophageal) echocardiography (2D TTE) and direct surgical visualization [3]. Obviously, 2D TTE is limited in visualizing the complete TA. Since real-time 3D echocardiography (RT3DE), has become available for clinical practice, it is now possible to examine the TV more completely [9]. The present study aimed to determine actual TA morphology, size and function with RT3DE and to compare the results with standard 2D TTE findings.
2. Subjects and methods
The study included forty consecutive patients with good image 2D TTE quality in whom also RT3DE was performed. Indications for echocardiography included follow-up for adult congenital heart disease (n=12), valvular heart disease (n=10), cardiomyopathy (n=8), and analysis of shortness of breath (n=10)
2D TTE was done with a Sonos 7500 ultrasound system attached to an S3 transducer (Philips, Best, The Netherlands). The TV was imaged from apical and parasternal views with the patient in the left lateral decubitus position. In each patient, the following variables were measured by two blinded observers: (1) TAD, obtained from the apical 4-chamber (AP4CH) and parasternal short axis (PSAX) views at an end-diastolic and end-systolic still frame, and (2) TA fraction shortening (TAFS) defined as (end-diastolic TAD-end-systolic TAD)/end-diastolic TAD obtained from the AP4CH and PSAX.
RT3DE was done with the same ultrasound system attached to a X4 matrix array transducer capable of providing real-time B-mode images. A full volume 3D data set was collected within approximately 5–10 s of breath holding in full volume mode from an apical window. The 3D daFta set was transferred for off-line analysis with TomTec software (Unterschleissheim, Munich, Germany). Data were stored digitally and subsequently evaluated by two blinded observers (AMA, OIIS). Data analysis of 3D images was based on a 2D approach relying on images obtained initially from the apical view. The TA was sliced between two narrow lines to exclude other tissues on the 2D image leading to clarification of annulus by a 3D image. This image was viewed and traced from the ventricular aspect, in 6 patients (15%) the atrial aspect was used because of better quality. Manual tracing of the inner border of the tricuspid annulus was done from the atrial aspect and once this was completed the surface area was automatically calculated and could be visualized from different points of views. Manual modification was made to correct any inconsistence.
The following RT3DE variables were obtained from both an end-diastolic and end-systolic still frame: (1) TA area (TAA3D), (2) major TAD3D defined as the widest TAD3D (see Fig. 1), and (3) minor TAD3D defined as the smallest TAD3D (see Fig. 1). Subsequently, TAFS3D was calculated from major TAD3D data and TA fractional area change (TAFAC3D) was calculated from systolic and diastolic TAA3D.
2.1. Statistical analysis
All data obtained by 2D TTE and RT3DE are presented as mean±S.D. A paired t-test was performed for comparing means of variables. The level of significance was set to P<0.05. An SPSS statistical package was used (SPSS, version 12.1, SPSS Inc, Chicago, IL). Interobserver agreement for 2D TTE and RT3DE measurements was assessed according to the Bland and Altman principle [10].
3. Results
In Table 1, the clinical and echocardiographic parameters of all patients are displayed. Patients were classified into two groups; group I included 20 patients with normal end-diastolic TAD2D-AP4CH (<35 mm) and group II included 20 patients with dilated end-diastolic TAD2D-AP4CH (35 mm). There were no significant differences in clinical variables (age, gender) between the two groups. All echocardiographic parameters were significantly higher in group II patients (all P<0.0001).
3.1. RT3DE acquisition
Acquisition and post-processing of RT3DE data was performed successfully in all patients in a reasonable time (approximately 1 min for acquisition and 5 min for data analysis). The TA was clearly delineated in all patients and, as seen in Fig. 1, its shape was not circular but oval, both in normal sized and in dilated TA (Fig. 2).
3.2. Comparison between 2D and 3D measurements
3.2.1. Diastolic values
There was a good correlation between end-diastolic TAD2D-AP4CH and TAD2D-PSAX (R=0.79, P<0.0001). Major TAD3D was well correlated with end-diastolic TAD2D-AP4CH and TAD2D-PSAX (R=0.74, P<0.0001 and R=0.75, P<0.0001, respectively). As seen in Table 1 and Fig. 2, major TAD3D measurements in both patient groups were significantly larger than end-diastolic TAD2D-AP4CH and TAD2D-PSAX. Also when the largest TAD2D was compared to TAD3D, 3D measurements were significantly larger (44.9±11.3 and 39.0±10.3 mm, P<0.001). After reclassification of the patients according to major TAD3D findings only 10 patients could be classified as normal (major TAD3D <35 mm). In these 10 patients actual TAD2D-AP4CH and TAD2D-PSAX values were 30.6±6.0 and 29.1±6.4 mm, respectively. Importantly, in patients with normal TAD2D, 65% of them had grade 1–2 TR (see Table 1) whereas in normal TAD3D only 30% of patients had grade 1–2 TR.
3.2.2. Systolic values
There was an excellent correlation between end-systolic TAD2D-AP4CH and TAD2D-PSAX (R=0.89, P<0.0001). Major systolic TAD3D measurements correlated well with end-systolic TAD2D-AP4CH and TAD2D-PSAX (R=0.80, P<0.0001 and R=0.66, P<0.05, respectively). As seen in Table 1, major systolic TAD3D measurements were in both patient groups significantly greater than end-systolic TAD2D-AP4CH and TAD2D-PSAX.
3.2.3. Fractional shortening
There were no significant differences between TAFS2D-AP4CH (14.2±7.1%), TAFS2D-PSAX (14.6±9.2%), and TAFS3D (17.8±13.2%). TAFAC3D was significantly higher than the aforementioned TAFS2D or TAFS3D measurements (26.6±12.7%; P<0.0001).
3.2.4. Minor TAD
No significant differences were detected between end-systolic and end-diastolic minor TAD3D versus TAD2D-AP4CH and TAD2D-PSAX in both groups (Table 1).
3.2.5. Interobserver agreement
As seen in Fig. 3, the limits of interobserver agreement for major TAD3D (mean difference –0.5±1.7 mm, agreement –3.9 to 2.9) were comparable to end-diastolic TAD2D-AP4CH (mean difference 0.1±2.0 mm, agreement –3.9 to 4.1). The limits of interobserver agreement for TAD2D-PSAX (mean difference 1.0±4.8 mm, agreement –3.8 to 5.8) were worse, in particular for lower TAD values.
4. Discussion
In the present study, the morphological and functional aspects of the TA were assessed by RT3DE. The main findings of our study are (1) TA shape was not circular but oval, both in normal sized and in dilated TA, (2) TAD is underestimated by 2D TTE, and (3) TAFS measurements are comparable for 2D TTE and RT3DE.
TAD measurements are of critical importance in the TV surgical decision-making process [11–13]. Absence of TR or the presence of only mild TR does not mean that the TV is free of any abnormality such as TA dilatation. At a given time, even considerable TA dilatation may not always result in significant TR [11,12]. Not only the selection of patients undergoing surgery for TR is dependent on echocardiographic TAD assessment [11], but also the type of surgical technique (valve plication or ring placement) is influenced by measurements of TA function and TAD [3,14].
Although 2D TTE is helpful to assess TV function and to detect TR severity it has important limitations in describing TV morphological details, such as TAD [13,14]. It is well known that after mitral valve surgery patients may clinically deteriorate due to underestimated TV pathology and significant residual or developing TR [15]. RT3DE may yield more detailed anatomical information. In the present study, the TA was visualized well in all subjects allowing even measurements of its area, both at end-systole and end-diastole. This is in accordance with a 3D study by Schnabel et al. [9] in which TA visualization was good or at least sufficient in over 90% of patients. When TAD2D measurements were compared with the TAD3D measurements, 2D measurements were significantly smaller than the major TAD3D measurements (diameter measured from the antero-septal to the antero-posterior commissure). In fact, TAD2D measurements corresponded more with the minor TAD3D measurements. In 2D TTE studies it was shown that the normal value for TAD is <35 mm [14]. However, in our study half of the patients with a normal TAD2D had an actual TAD (measured with 3D) larger than 35 mm. So, 2D TTE cannot be relied on defining TAD as normal. It seems necessary to re-establish normal TAD values with 3D imaging. Importantly, interobserver agreement for TAD3D measurements was comparable to TAD2D-AP4CH measurements and better than TAD2D-PSAX measurements. If 2D TTE is the only available assessment tool for TAD, the apical 4-chamber view seems preferred because of better interobserver agreement compared to TAD2D-PSAX and more alignment with TAD3D measurements.
Like other cardiac structures, cyclic changes occur in TAD during systole and diastole [3,11,15]. Calculation of TAFS from systolic and diastolic TAD showed no difference between 2D TTE and RT3DE. This is because end-systolic and end-diastolic TAD3D values are to an equal extent increased compared with 2D values.
Calculation of TA function by TAFAC3D was significantly higher than that measured by diameter changes either in 2D TTE or RT3DE. This could be explained by the accuracy of global function by area percent changes than single distance percent changes especially when more lengthening occurs.
In accordance with a previous study [12] that reported no relation between presence and severity of TR and degree of TA dilatation when 2D TTE was relied on as 65% of normal TAD2D had grade 1–2 TR, but with normal major TAD3DE, the percentage decreased to 30%.
4.1. Study limitation
The main limitation of this study is that RT3DE data were not compared with a ‘gold standard’ such as magnetic resonance imaging or surgical findings. Nevertheless, our main findings (oval shape of the TA, larger TAD3D) were consistently found in the large majority of patients. Also, RT3DE images more critically depend on image quality than 2D TTE images and the value of RT3DE should be assessed in a more non-selected (image quality) population.
5. Conclusions
The TA is an oval structure with a major and a minor diameter. 2D TTE underestimates TAD, regardless whether it is measured from the apical 4-chamber or parasternal short axis view. This may have important implications in the TV surgical decision-making processes.
Acknowledgements
I would like to express my thanks to Dr Osama I. Soliman and Mr Rene Frowijn for their help and support to finish this work
References
Silver MD, Lam JH, Ranganathan N, Wigle ED. Morphology of the human tricuspid valve. Circulation 1971; 43:333–348.
Yacoub MH, Cohn LH. Novel approaches to cardiac valve repair: from structure to function: Part II. Circulation 2004; 109:1064–1072.
Colombo T, Russo C, Ciliberto GR, Lanfranconi M, Bruschi G, Agati S, Vitali E. Tricuspid regurgitation secondary to mitral valve disease: tricuspid annulus function as guide to tricuspid valve repair. CardioVasc Surg 2001; 9:369–377.
Cohn LH. Tricuspid regurgitation secondary to mitral valve disease: when and how to repair. J Card Surg 1994; 9:237–241.
Tei C, Pilgrim JP, Shah PM, Ormiston JA, Wong M. The tricuspid valve annulus: study of size and motion in normal subjects and in patients with tricuspid regurgitation. Circulation 1982; 66:665–671.
Ubago JL, Figueroa A, Ochoteco A, Colman T, Duran RM, Duran CG. Analysis of the amount of tricuspid valve anular dilatation required to produce functional tricuspid regurgitation. Am J Cardiol 1983; 52:155–158.
Shemin R. Tricuspid valve disease. In: Cohn LH, Edmunds Jr LH. eds. Cardiac surgery in the adults2003;New York: McGraw-Hill In:.
McGrath LB G-lL, Bailey BM. Tricuspid valve operation in 530 patients. Twenty-five-year assessment of early and late phase events. J Thorac CardioVasc Surg 1990; 99:124–133.
Schnabel R, Khaw AV, von Bardeleben RS, Strasser C, Kramm T, Meyer J, Mohr-Kahaly S. Assessment of the tricuspid valve morphology by transthoracic real-time-3D-echocardiography. Echocardiography 2005; 22:15–23.
Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1:307–310.
Goldman ME, Guarino T, Fuster V, Mindich B. The necessity for tricuspid valve repair can be determined intraoperatively by two-dimensional echocardiography. J Thorac CardioVasc Surg 1987; 94:542–550.
Chopra HK, Nanda NC, Fan P, Kapur KK, Goyal R, Daruwalla D, Pacifico A. Can two-dimensional echocardiography and Doppler color flow mapping identify the need for tricuspid valve repair J Am Coll Cardiol 1989; 14:1266–1274.
De Simone R, Lange R, Tanzeem A, Gams E, Hagl S. Adjustable tricuspid valve annuloplasty assisted by intraoperative transesophageal color Doppler echocardiography. Am J Cardiol 1993; 71:926–931.
Dreyfus GD, Corbi PJ, Chan KM, Bahrami T. Secondary tricuspid regurgitation or dilatation: which should be the criteria for surgical repair. Ann Thorac Surg 2005; 79:127–132.
Tager R, Skudicky D, Mueller U, Essop R, Hammond G, Sareli P. Long-term follow-up of rheumatic patients undergoing left-sided valve replacement with tricuspid annuloplasty-validity of preoperative echocardiographic criteria in the decision to perform tricuspid annuloplasty. Am J Cardiol 1998; 81:1013–1016.(Ashraf M. Anwar, Marcel L)
b Cardiology Department, Al-Husein University Hospital, Al-Azhar University, Cairo, Egypt
Abstract
Tricuspid annulus (TA) evaluation continues to be a major problem in the surgical decision-making process. Obviously, 2-dimensional transthoracic echocardiography (2D TTE) is limited in TA visualization due to its complex 3D shape. The study aimed to determine TA morphology, size and function with real-time three-dimensional echocardiography (RT3DE) in 40 patients divided into two equal groups (I: normal TA and II: dilated). 2D TTE measurements included TA diameter (TAD) at apical 4-chamber (AP4CH) and parasternal short axis (PSAX) views. RT3DE measurements included TA area (TAA), major TAD and minor TAD. TA fractional shortening (TAFS), and TA fractional area change (TAFAC) were calculated from end-systolic and end-diastolic measurements. RT3DE allowed visualization and measurement of the entire oval-shaped TA in all patients irrespective of its size (normal or dilated). 2D TTE measurement of TAD at both AP4CH and at PSAX views was significantly smaller than the major TAD measured by RT3DE (P<0.0001) and nearly matched with the minor TAD in all patients. Calculation of TAFS was comparable with both techniques. TAFAC was significantly higher than TAFS (P<0.0001). So, RT3DE could be relied on more accurately than 2D TTE in the assessment of TA size and function which may aid in decision-making and selection of proper surgical procedure when indicated.
Key Words: Tricuspid annulus; Real-time 3D echocardiography
1. Introduction
The tricuspid valve (TV) is composed of three leaflets (anterior, posterior and septal) attached to a fibrous annulus [1]. The three-dimensional (3D) shape of this tricuspid annulus (TA) is complex and does not conform to a flat ring [2]. Tricuspid regurgitation (TR) is the most common pathology affecting the TV. An understanding of the pathological process underlying TR is necessary to determine the optimal management strategy. Usually, TR is secondary to left-sided valvular pathology (mostly mitral valve disease) with pulmonary hypertension and right ventricular dilatation [3,4]. Because the TA is a component of the right ventricle it will dilate also. However, since the septal leaflet is fixed between the fibrous trigones, the TA can only lengthen and dilate along the attachment of the anterior and posterior leaflets [5–7]. Unfortunately, TV evaluation continues to be a major problem in the surgical decision-making process [8]. Guidelines for TV repair include TA assessment (indexed TA size 2.1 cm/m2 and TA fractional shortening <25%) [3]. At the time of surgery the decision to repair the TV may be changed due to discrepant TA diameter (TAD) findings between pre-operative two-dimensional transthoracic (or transesophageal) echocardiography (2D TTE) and direct surgical visualization [3]. Obviously, 2D TTE is limited in visualizing the complete TA. Since real-time 3D echocardiography (RT3DE), has become available for clinical practice, it is now possible to examine the TV more completely [9]. The present study aimed to determine actual TA morphology, size and function with RT3DE and to compare the results with standard 2D TTE findings.
2. Subjects and methods
The study included forty consecutive patients with good image 2D TTE quality in whom also RT3DE was performed. Indications for echocardiography included follow-up for adult congenital heart disease (n=12), valvular heart disease (n=10), cardiomyopathy (n=8), and analysis of shortness of breath (n=10)
2D TTE was done with a Sonos 7500 ultrasound system attached to an S3 transducer (Philips, Best, The Netherlands). The TV was imaged from apical and parasternal views with the patient in the left lateral decubitus position. In each patient, the following variables were measured by two blinded observers: (1) TAD, obtained from the apical 4-chamber (AP4CH) and parasternal short axis (PSAX) views at an end-diastolic and end-systolic still frame, and (2) TA fraction shortening (TAFS) defined as (end-diastolic TAD-end-systolic TAD)/end-diastolic TAD obtained from the AP4CH and PSAX.
RT3DE was done with the same ultrasound system attached to a X4 matrix array transducer capable of providing real-time B-mode images. A full volume 3D data set was collected within approximately 5–10 s of breath holding in full volume mode from an apical window. The 3D daFta set was transferred for off-line analysis with TomTec software (Unterschleissheim, Munich, Germany). Data were stored digitally and subsequently evaluated by two blinded observers (AMA, OIIS). Data analysis of 3D images was based on a 2D approach relying on images obtained initially from the apical view. The TA was sliced between two narrow lines to exclude other tissues on the 2D image leading to clarification of annulus by a 3D image. This image was viewed and traced from the ventricular aspect, in 6 patients (15%) the atrial aspect was used because of better quality. Manual tracing of the inner border of the tricuspid annulus was done from the atrial aspect and once this was completed the surface area was automatically calculated and could be visualized from different points of views. Manual modification was made to correct any inconsistence.
The following RT3DE variables were obtained from both an end-diastolic and end-systolic still frame: (1) TA area (TAA3D), (2) major TAD3D defined as the widest TAD3D (see Fig. 1), and (3) minor TAD3D defined as the smallest TAD3D (see Fig. 1). Subsequently, TAFS3D was calculated from major TAD3D data and TA fractional area change (TAFAC3D) was calculated from systolic and diastolic TAA3D.
2.1. Statistical analysis
All data obtained by 2D TTE and RT3DE are presented as mean±S.D. A paired t-test was performed for comparing means of variables. The level of significance was set to P<0.05. An SPSS statistical package was used (SPSS, version 12.1, SPSS Inc, Chicago, IL). Interobserver agreement for 2D TTE and RT3DE measurements was assessed according to the Bland and Altman principle [10].
3. Results
In Table 1, the clinical and echocardiographic parameters of all patients are displayed. Patients were classified into two groups; group I included 20 patients with normal end-diastolic TAD2D-AP4CH (<35 mm) and group II included 20 patients with dilated end-diastolic TAD2D-AP4CH (35 mm). There were no significant differences in clinical variables (age, gender) between the two groups. All echocardiographic parameters were significantly higher in group II patients (all P<0.0001).
3.1. RT3DE acquisition
Acquisition and post-processing of RT3DE data was performed successfully in all patients in a reasonable time (approximately 1 min for acquisition and 5 min for data analysis). The TA was clearly delineated in all patients and, as seen in Fig. 1, its shape was not circular but oval, both in normal sized and in dilated TA (Fig. 2).
3.2. Comparison between 2D and 3D measurements
3.2.1. Diastolic values
There was a good correlation between end-diastolic TAD2D-AP4CH and TAD2D-PSAX (R=0.79, P<0.0001). Major TAD3D was well correlated with end-diastolic TAD2D-AP4CH and TAD2D-PSAX (R=0.74, P<0.0001 and R=0.75, P<0.0001, respectively). As seen in Table 1 and Fig. 2, major TAD3D measurements in both patient groups were significantly larger than end-diastolic TAD2D-AP4CH and TAD2D-PSAX. Also when the largest TAD2D was compared to TAD3D, 3D measurements were significantly larger (44.9±11.3 and 39.0±10.3 mm, P<0.001). After reclassification of the patients according to major TAD3D findings only 10 patients could be classified as normal (major TAD3D <35 mm). In these 10 patients actual TAD2D-AP4CH and TAD2D-PSAX values were 30.6±6.0 and 29.1±6.4 mm, respectively. Importantly, in patients with normal TAD2D, 65% of them had grade 1–2 TR (see Table 1) whereas in normal TAD3D only 30% of patients had grade 1–2 TR.
3.2.2. Systolic values
There was an excellent correlation between end-systolic TAD2D-AP4CH and TAD2D-PSAX (R=0.89, P<0.0001). Major systolic TAD3D measurements correlated well with end-systolic TAD2D-AP4CH and TAD2D-PSAX (R=0.80, P<0.0001 and R=0.66, P<0.05, respectively). As seen in Table 1, major systolic TAD3D measurements were in both patient groups significantly greater than end-systolic TAD2D-AP4CH and TAD2D-PSAX.
3.2.3. Fractional shortening
There were no significant differences between TAFS2D-AP4CH (14.2±7.1%), TAFS2D-PSAX (14.6±9.2%), and TAFS3D (17.8±13.2%). TAFAC3D was significantly higher than the aforementioned TAFS2D or TAFS3D measurements (26.6±12.7%; P<0.0001).
3.2.4. Minor TAD
No significant differences were detected between end-systolic and end-diastolic minor TAD3D versus TAD2D-AP4CH and TAD2D-PSAX in both groups (Table 1).
3.2.5. Interobserver agreement
As seen in Fig. 3, the limits of interobserver agreement for major TAD3D (mean difference –0.5±1.7 mm, agreement –3.9 to 2.9) were comparable to end-diastolic TAD2D-AP4CH (mean difference 0.1±2.0 mm, agreement –3.9 to 4.1). The limits of interobserver agreement for TAD2D-PSAX (mean difference 1.0±4.8 mm, agreement –3.8 to 5.8) were worse, in particular for lower TAD values.
4. Discussion
In the present study, the morphological and functional aspects of the TA were assessed by RT3DE. The main findings of our study are (1) TA shape was not circular but oval, both in normal sized and in dilated TA, (2) TAD is underestimated by 2D TTE, and (3) TAFS measurements are comparable for 2D TTE and RT3DE.
TAD measurements are of critical importance in the TV surgical decision-making process [11–13]. Absence of TR or the presence of only mild TR does not mean that the TV is free of any abnormality such as TA dilatation. At a given time, even considerable TA dilatation may not always result in significant TR [11,12]. Not only the selection of patients undergoing surgery for TR is dependent on echocardiographic TAD assessment [11], but also the type of surgical technique (valve plication or ring placement) is influenced by measurements of TA function and TAD [3,14].
Although 2D TTE is helpful to assess TV function and to detect TR severity it has important limitations in describing TV morphological details, such as TAD [13,14]. It is well known that after mitral valve surgery patients may clinically deteriorate due to underestimated TV pathology and significant residual or developing TR [15]. RT3DE may yield more detailed anatomical information. In the present study, the TA was visualized well in all subjects allowing even measurements of its area, both at end-systole and end-diastole. This is in accordance with a 3D study by Schnabel et al. [9] in which TA visualization was good or at least sufficient in over 90% of patients. When TAD2D measurements were compared with the TAD3D measurements, 2D measurements were significantly smaller than the major TAD3D measurements (diameter measured from the antero-septal to the antero-posterior commissure). In fact, TAD2D measurements corresponded more with the minor TAD3D measurements. In 2D TTE studies it was shown that the normal value for TAD is <35 mm [14]. However, in our study half of the patients with a normal TAD2D had an actual TAD (measured with 3D) larger than 35 mm. So, 2D TTE cannot be relied on defining TAD as normal. It seems necessary to re-establish normal TAD values with 3D imaging. Importantly, interobserver agreement for TAD3D measurements was comparable to TAD2D-AP4CH measurements and better than TAD2D-PSAX measurements. If 2D TTE is the only available assessment tool for TAD, the apical 4-chamber view seems preferred because of better interobserver agreement compared to TAD2D-PSAX and more alignment with TAD3D measurements.
Like other cardiac structures, cyclic changes occur in TAD during systole and diastole [3,11,15]. Calculation of TAFS from systolic and diastolic TAD showed no difference between 2D TTE and RT3DE. This is because end-systolic and end-diastolic TAD3D values are to an equal extent increased compared with 2D values.
Calculation of TA function by TAFAC3D was significantly higher than that measured by diameter changes either in 2D TTE or RT3DE. This could be explained by the accuracy of global function by area percent changes than single distance percent changes especially when more lengthening occurs.
In accordance with a previous study [12] that reported no relation between presence and severity of TR and degree of TA dilatation when 2D TTE was relied on as 65% of normal TAD2D had grade 1–2 TR, but with normal major TAD3DE, the percentage decreased to 30%.
4.1. Study limitation
The main limitation of this study is that RT3DE data were not compared with a ‘gold standard’ such as magnetic resonance imaging or surgical findings. Nevertheless, our main findings (oval shape of the TA, larger TAD3D) were consistently found in the large majority of patients. Also, RT3DE images more critically depend on image quality than 2D TTE images and the value of RT3DE should be assessed in a more non-selected (image quality) population.
5. Conclusions
The TA is an oval structure with a major and a minor diameter. 2D TTE underestimates TAD, regardless whether it is measured from the apical 4-chamber or parasternal short axis view. This may have important implications in the TV surgical decision-making processes.
Acknowledgements
I would like to express my thanks to Dr Osama I. Soliman and Mr Rene Frowijn for their help and support to finish this work
References
Silver MD, Lam JH, Ranganathan N, Wigle ED. Morphology of the human tricuspid valve. Circulation 1971; 43:333–348.
Yacoub MH, Cohn LH. Novel approaches to cardiac valve repair: from structure to function: Part II. Circulation 2004; 109:1064–1072.
Colombo T, Russo C, Ciliberto GR, Lanfranconi M, Bruschi G, Agati S, Vitali E. Tricuspid regurgitation secondary to mitral valve disease: tricuspid annulus function as guide to tricuspid valve repair. CardioVasc Surg 2001; 9:369–377.
Cohn LH. Tricuspid regurgitation secondary to mitral valve disease: when and how to repair. J Card Surg 1994; 9:237–241.
Tei C, Pilgrim JP, Shah PM, Ormiston JA, Wong M. The tricuspid valve annulus: study of size and motion in normal subjects and in patients with tricuspid regurgitation. Circulation 1982; 66:665–671.
Ubago JL, Figueroa A, Ochoteco A, Colman T, Duran RM, Duran CG. Analysis of the amount of tricuspid valve anular dilatation required to produce functional tricuspid regurgitation. Am J Cardiol 1983; 52:155–158.
Shemin R. Tricuspid valve disease. In: Cohn LH, Edmunds Jr LH. eds. Cardiac surgery in the adults2003;New York: McGraw-Hill In:.
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