Functional Grading of a Transversely Isotropic Hyperelastic Model with Applications in Modeling Tricuspid and Mitral Valve Transition Regions

Surgical simulators and injury-prediction human models require a combination of representative tissue geometry and accurate tissue material properties to predict realistic tool-tissue interaction forces and injury mechanisms, respectively. While biological tissues have been individually characterized, the transition regions between tissues have received limited research attention, potentially resulting in inaccuracies within simulations. In this work, an approach to characterize the transition regions in transversely isotropic (TI) soft tissues using functionally graded material (FGM) modeling is presented. The effect of nonlinearities and multi-regime nature of the TI model on the functional grading process is discussed. The proposed approach has been implemented to characterize the transition regions in the leaflet (LL), chordae tendinae (CT) and the papillary muscle (PM) of porcine tricuspid valve (TV) and mitral valve (MV). The FGM model is informed using high resolution morphological measurements of the collagen fiber orientation and tissue composition in the transition regions, and deformation characteristics predicted by the FGM model are numerically validated to experimental data using X-ray diffraction imaging. The results indicate feasibility of using the FGM approach in modeling soft-tissue transitions and has implications in improving physical representation of tissue deformation throughout the body using a scalable version of the proposed approach.

Longitudinal Reference Ranges for Tricuspid Annular Plane Systolic Excursion and Mitral Annular Plane Systolic Excursion in Normally Grown Fetuses

OBJECTIVES

The aim of this study was to construct reference ranges for fetal tricuspid annular plane systolic excursion (TAPSE) and mitral annular plane systolic excursion (MAPSE) using conventional M-mode ultrasound (US) in the second half of pregnancy.

METHODS

Participants underwent US scans every 4 weeks from 18 weeks' gestation until delivery. The TAPSE and MAPSE were measured by conventional M-mode US at each examination. The relationships between TAPSE and MAPSE and gestational age and estimated fetal weight were modeled by Bayesian mixed effects linear regression.

RESULTS

Positive linear relationships were observed between both MAPSE and TAPSE and gestational age and estimated fetal weight. Reference centiles for TAPSE and MAPSE were developed.

CONCLUSIONS

This simple technique is a useful tool for assessing cardiac function and could be used for quantitative assessments of fetal cardiac function, particularly in high-risk pregnancies such as those complicated by maternal diabetes.

Normal Reference Values and Reproducibility of Tricuspid Annulus Dimensions Using Cardiovascular Magnetic Resonance

Tricuspid annular (TA) dilation is a key process in functional tricuspid regurgitation, but normal TA dimensions using cardiovascular magnetic resonance have not been established. We measured TA diameters in 66 healthy volunteers, aged 38 ± 11 years, during 3 different phases of the cardiac cycle (end-systole, early diastole, and end-diastole) and in 2 routinely acquired cardiovascular magnetic resonance imaging planes (4-chamber [4C] and right ventricular inflow-outflow [RVIO]). Three readers independently measured each value and 1 reader repeated measurements 1 month apart. The upper limit of normal (ULN) was calculated as 1.96 standard deviations above the mean. We assessed inter- and intraobserver reliability using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. We found the TA diameter largest during early diastole in the 4C view with an ULN of 43 mm (22 mm/m²). Men had larger absolute TA diameters (36 mm, 95% CI 27 to 44 mm) than women (30 mm, 95% CI 23 to 37 mm) but not after indexing for body surface area (both 18 mm/m²). In the RVIO view, the largest TA diameter occurred during early diastole with a ULN value of 46 mm (27 mm/m²). In this view, females had a larger indexed TA than men (21 mm/m² vs 17 mm/m²). Reproducibility of measurements was excellent in all cardiac phases with an inter-rater ICC between 0.90 to 0.96 and an intrarater ICC 0.89 to 0.96. In conclusion, we have provided normative data regarding TA dimensions in routinely acquired 4C and RVIO views, and these values are larger than the current thresholds of annular dilation measured by echocardiography. Gender differences with the TA diameter in the RVIO view may be an important finding with consideration of future tricuspid devices.

Specific Anatomic Considerations for Tricuspid Interventions

PURPOSE OF REVIEW

This review discusses the normal anatomy and pathology of the tricuspid valve (TV) and right side of the heart. Emphasis is on those anatomic and pathologic features relevant to interventions intended to restore normal function to the TV in disease states.

RECENT FINDINGS

TV pathology is less common than aortic and mitral valve pathology, and treatment and outcomes for interventions face considerable hurdles. New innovations and early data showing safety and efficacy in transcatheter interventions have transformed TV interventions into the next frontier in cardiac valve disease treatment. Certain features of the TV and right heart have presented themselves as potential targets, as well as impediments, for TV intervention. The causes of TV pathology and the anatomy of the TV and right heart bring unique challenges to intervention. Approaches to intervention will continue to progress and change the way we view and treat TV pathology.

New insight into tricuspid valve anatomy from 100 hearts to reappraise annuloplasty methodology

OBJECTIVE

Prosthetic ring annuloplasty plays an important role in tricuspid valve repair. However, discussions regarding the appropriate suturing technique for rigid annuloplasty rings in patients with tricuspid valve anatomical variations are lacking. We aimed to clarify the diversity and pattern of tricuspid valve morphology.

METHODS

We analyzed tricuspid valve morphology and measured leaflet dimensions in 100 autopsy hearts, which were classified into three groups based on the number of posterior leaflet scallops: single scallop (PLS1) (n = 52), two scallops (PLS2) (n = 42), and three scallops (PLS3) (n = 5). One heart without posterior leaflet was excluded from the statistical analysis. Demographic characteristics were compared between PLS1, PLS2, and PLS3. The linear trends of proportions of each leaflet between PLS1, PLS2, and PLS3 were assessed using linear regression analysis.

RESULTS

Median proportion (interquartile range) of the posterior annular length out of the entire annular perimeter in PLS1, PLS2, and PLS3 was 26% (22-31%), 37% (33-40%), and 45% (42-49%), respectively. Linear regression analysis showed a significant increasing trend (p for trend < 0.001) of the posterior leaflet annulus proportion from PLS1 to PLS3. Accordingly, the anterior and septal annulus proportions significantly decreased from PLS1 to PLS3.

CONCLUSIONS

Approximately half of the tricuspid valve has multiple posterior leaflet scallops. The proportion of the posterior leaflet annular length to the tricuspid valve annulus perimeter increases as the number of posterior leaflet scallops increases. These morphologic variations will be fundamental for future discussion about the pathology of a dilated tricuspid valve and methodology of prosthetic ring annuloplasty.

Porcine Tricuspid Valve Anatomy and Human Compatibility: Relevance for Preclinical Validation of Novel Valve Interventions

BACKGROUND

Tricuspid regurgitation may be a precursor for heart failure, reduced functional capacity, and poor survival. A human compatible experimental model is required to understand the pathophysiology of the tricuspid valve disease as a basis for validating novel tricuspid valve interventions before clinical use. The study aim was to evaluate and compare the tricuspid valve anatomy of porcine and human hearts.

METHODS

The anatomy of the tricuspid valve and the surrounding structures that affect the valve during a cardiac cycle were examined in detail in 100 fresh and 19 formalin-fixed porcine hearts obtained from Danish Landrace pigs (body weight 80 kg). All valvular dimensions were compared with human data acquired from literature sources.

RESULTS

No difference was seen in the tricuspid annulus circumference between porcine and human hearts (13.0 ± 1.2 cm versus 13.5 ± 1.5 cm; p = NS), or in valve area (5.7 ± 1.6 cm2 versus 5.6 ± 1.0 cm2; p = NS). The majority of chordae types exhibited a larger chordal length and thickness in human hearts compared to porcine hearts. In both species, the anterior papillary muscle (PM) was larger than other PMs in the right ventricle, but muscle length varied greatly (range: 5.2-40.3 mm) and was significantly different in pigs and in humans (12.2 ± 3.2 mm versus 19.2 mm; p <0.001).

CONCLUSIONS

The porcine tricuspid valve was determined to be a valid model for preclinical animal studies, despite various anatomic differences being noted between porcine and human hearts.

Differential and linear insertion of atrioventricular valves: a useful tool?

OBJECTIVE

The differential insertion of the atrioventricular valves is the ultrasonographic representation of the more apical attachment of the tricuspid valve to the septum with respect to the mitral valve. A linear insertion is present when both valves form a linear continuum and has been suggested as a marker for atrioventricular septal defects (AVSDs). The objective of this study was to evaluate the anatomical substratum of differential and linear insertions of the atrioventricular valves in normal fetal hearts and fetal hearts with an AVSD.

METHODS

The extent and position of the fibrous skeleton and attachment of the atrioventricular valves to the septum were studied in histological sections of 17 normal hearts and four hearts with an AVSD from 10 + 0 weeks' gestation to 3 days postpartum with various immunohistochemical tissue markers. In addition, spatiotemporal image correlation (STIC) volumes of 10 normal hearts and STIC volumes of eight hearts with an AVSD at 13 + 6 to 35 + 5 weeks' gestation were examined.

RESULTS

The differential insertion of the atrioventricular valves was visible in normal hearts in the four-chamber plane immediately beneath the aorta, but nearer the diaphragm a linear insertion was found. In hearts with an AVSD, a linear appearance was observed in the four-chamber plane immediately beneath the aorta. Towards the diaphragm, however, first a differential insertion and, more caudally, a linear insertion was found.

CONCLUSIONS

Both differential and linear insertions can be found in normal fetal hearts and fetal hearts with AVSD, depending on the plane in which the four-chamber view is visualized. Therefore, measurement of the differential insertion is likely to be useful only in experienced hands.

Relation of cuspal asymmetry to development of aortic stenosis in adults with tricuspid aortic valves

BACKGROUND AND AIM OF THE STUDY

The contribution of aortic valve (AV) cusp asymmetry to the future development of aortic stenosis (AS) has not been studied.

METHODS

Of the 412,458 patients that underwent echocardiography between January 2003 and January 2011 at the Cleveland Clinic, 34,326 with aortic stenosis (AS) were identified from the Echocardiography Database. Among these patients, 5,830 had undergone echocardiography on more than one occasion. The review identified 71 patients who had tricuspid AV without stenosis, sclerosis or calcification, who met the study criteria, and who ultimately developed AS at a mean of 56.5 ± 19.4 months after the initial echocardiogram. Comprehensive echocardiographic AV cusp measurements taken from these echocardiograms were compared to those of 71 age- and gender-matched control subjects without AS.

RESULTS

In the AS group, 11 patients (15.4%) had three equal-sized AV cusps, six (8.4%) had two equal-sized cusps, and 54 (76.1%) had three different-sized cusps. In the control group, 70 subjects (98.6%) had three equal-sized AV cusps, none had two equal-sized cusps, and one subject (1.4%) had three different-sized cusps. The average asymmetry index (AIx; %) among all the corresponding cusp measurements was significantly larger in the AS group (p = 0.000). Among the 71 AS patients, 32 developed mild AS, 30 moderate AS, and nine severe AS. The average AIx did not differ significantly based on AS severity.

CONCLUSION

The presence of asymmetry among AV cusps is strongly associated with the future development of AS. The present data suggest that a non-laminar flow secondary to an asymmetric valve may predispose the AV to become stenotic.

Sex variations in the structure of human atrioventricular annuli

Atrioventricular annuli are important in haemodynamic flexibility, competence, and support for tricuspid and mitral valves. The anatomical features of the annuli, such as circumference, organisation of connective tissue fibres, myocardium, and cellularity, may predispose to annular insufficiency and valvular incompetence. These pathologies occur more commonly in females, although the anatomical basis for this disparity is unclear. Sex variation in the structure of the annuli is important in providing a morphological basis for the patterns of these diseases. This study therefore aimed to determine the sex variations in the structure of human atrioventricular annuli. One hundred and one hearts (48 males, 53 females) obtained from the Department of Human Anatomy of the University of Nairobi were studied. Annular circumferences were measured using a flexible ruler and corrected for heart weight. Results were analysed using SPSS version 17.0 and sex differences determined using student's t-test. A p-value of less than 0.05 was considered significant. For light microscopy, specimens were harvested within 48 hours post-mortem, processed, sectioned, and stained with Masson's trichrome and Weigert's elastic stain with van Gieson counterstaining. Females had significantly larger annular circumferences than males after correcting for heart weight (p ≤ 0.05). Histologically, myocardium was consistently present in all male annuli while this was absent in females except in one specimen. The annuli were more elastic and cellular in males especially in the annulo-myocardial and annulo-valvular zones, respectively. The corrected larger annular circumference in females may limit heart valve coaptation during cardiac cycle and may be a risk factor for valvular insufficiency. The predominance of myocardium, annular cellularity, and elasticity may be more protective against heart valve incompetence in males than in females.

Anatomy of the septomarginal trabecula in goat hearts

Our aim in this study was to examine the right septomarginal trabecula of goats regarding the frequency, origin course of the septal and free component, attachment to the papillaris magnus muscle and size . The material used consisted in 32 hearts from non-pedigree goats of both sexes, preserved in 10% formalin. The right septomarginal trabecula was present in all hearts. It could also present a prominence in the form of a cord in the septum before detaching and going towards the wall or the papillary muscle. We called this a septal component and found it in 69% of all hearts studied. In the remaining specimens, the exit of the septomarginal trabecula was abrupt, without presenting a septal component. It could be attached solely to the papillaris magnus muscle or to the papillary muscle and the ventricle wall, originated in the cranial third of the septum, and was attached to the middle third of the papillary muscle or its caudal third. Its free part, from the septum to the papillaris magnus muscle, ranged in length from 1.3 cm to 2.6 cm. The mean value was 1.7 cm, and the most frequent values were 1.9 and 1.5 cm. In conclusion, in goats, the septomarginal trabecula is a constant and invariable structure.

Evaluation of the tricuspid valve morphology and function by transthoracic real-time three-dimensional echocardiography

Assessment of tricuspid valve (TV) function plays an important role in a number of clinical disease states, including left-sided valve disease and heart failure. However, the TV is a complex structure that, unlike the aortic and mitral valve, it is not possible to visualize in one cross-sectional view using either transthoracic or transoesophageal two-dimensional echocardiography (i.e. imaging all three TV leaflets and their attachment in the annulus simultaneously). Conversely, three-dimensional echocardiography allows users to visualize the whole TV apparatus from any perspective. This may significantly improve our understanding of the pathophysiological mechanisms underlying the various TV diseases and functional tricuspid regurgitation, and potentially suggest ways to improve surgical treatment. This review details the current status of real-time three-dimensional echocardiography evaluation of TV morphology and function with its clinical applications and limitations.

Microscopic study of right fibrous annulus

The term annulus fibrous is still used in anatomical and clinical terminology but does not exist in anatomical nomenclature. This structure is proposed as an anatomical substrate for circus movement of excitation. Multiple cardiac damage after blunt chest trauma is rare, but usually affects the septal part of the right fibrous annulus. Histological observation confirms the results of our previous macroscopic study and shows that the most stable part of fibrous annulus is the septal part and the region of anterior angle of the right ventricle, and the most labile parts are the lateral and posterior angles of the right ventricle and the posterior part of the fibrous annulus. Our histological study shows that the right fibrous annulus is a heterogeneous structure and may play a role in changes of shape of the right atrio-ventricular ostium during human life.

The relationship between the membranous part of the interventricular septum and the septal part of the attachment of the tricuspid valve in adult human hearts

The membranous septum is a difficult structure to demonstrate in vivo. It is possible to measure its dimensions in a cadaver after the introduction of light into the aorta, but difficult to do so otherwise. The present study was performed on a group of 107 formalin-fixed adult hearts from both sexes and 18-90 years of age. The hearts were divided into groups depending on sex and age. The length of the septal part of the attachment of the tricuspid valve was divided by the length of the supravalvular part of the membranous interventricular septum.

Anatomy of the tendinous cords of the interventricular septum of the human heart

There are frequent citations in the literature stating that lesions of the tendinous cords cause functional disorders of the heart valves. This led us to conduct the present investigation on the anatomy of the tendinous cords. Our objective was to focus on the morphological characteristics of tendinous cords that are inserted directly into the interventricular septum, such as their frequency, number, dimensions and This study was conducted on 50 hearts from adults of both sexes that had been fixed in 10% formaldehyde. The right ventricle was opened by means of an incision parallel to the anterior interventricular groove, and the left ventricle was opened by means of a longitudinal incision in the middle of the pulmonary (left) surface. Our results showed that, in the right ventricle, these tendinous cords constantly appeared without the involvement of papillary muscles (98%). They ranged in number from one to ten, and between two and five was the most common (72%). They were short, mostly ranging from 0.3 to 1.9 cm in length (81.5%) and were preferentially located in the upper third of the interventricular septum (71.4%). They were usually attached to the septal cusp (76.7%) and sometimes to the anterior cusp (21.3%). The cusp insertion sites were the free edge (62%), ventricular surface (32%) and basal edge (6%). It was exceptional to find tendinous cords in the ventricular septum of the left ventricle. Tendinous cords directly inserted into the atrioventricular septum were constantly present in the right ventricle, with varying numbers. They were predominantly short because they were inserted into the upper third of the septum and most often headed towards the septal cusp. It was exception to find tendinous cords in the atrioventricular septum of the left ventricle.

Morphometric features of the right atrioventricular orifice in adult human hearts

The normal data of the tricuspid valve complex is of great clinical importance in the light of progress in cardiosurgery and the development of novel operating techniques. A range of measurements for the right atrioventricular orifice in 96 human adult hearts was examined by means of anatomical dissection, inspection, examination, and statistical analyses. The length of the attachment of the anterior leaflet increased significantly between group I (aged 18-40 years) and group II (aged 41-64 years) in women only. In men there were no significant differences in this parameter between any of the three age groups. In addition, the attachment length of the posterior leaflet in women increased statistically in the second age group. In men, in contrast, the attachment length of the posterior leaflet did not increase significantly between the first and second age groups and became significantly larger only in oldest age group, consisting of men aged over 65. No statistically significant differences between the three age groups were found for the attachment length of the septal leaflet (p>0.05). In female hearts significant increases in the frontal and sagittal dimensions of the tricuspid valve orifice were observed between the second age group and the group aged over 65. In male hearts both the frontal and sagittal dimensions increased significantly with advanced age. The right atrioventricular orifice expressed as the ellipse area was statistically greater than the triangular area (p<0.01) in each age group. It should be noticed that both areas increased significantly during ageing. This study has demonstrated that the shape of the right atrioventricular orifice evolves during life, from a triangular shape to a more elliptical shape.

The morphometry of the accessory leaflets of the tricuspid valve in a four cuspidal model

The tricuspid valve is of great importance because of the progress made in operative techniques and invasive cardiology accidents. This structure is more differentiated during evolution than the mitral valve. Accessory leaflets, their frequency and role are still controversial, despite the fact that they have been known from the beginning of the 20th century. The number of leaflets in the tricuspid valve grows in an evolutionary line, but the rules governing their appearance are still not known. The samples were taken from a group of 107 human adult hearts. The four-cuspidal form of the tricuspid valve was used as the simplest model to show the appearance of accessory leaflets for anatomical and statistical examination. On the basis of the results of this study we conclude that the separation of accessory leaflets is a complex process.

The morphology and distribution of the tendinous chords and their relation to the papillary muscles in the tricuspid valve of the human heart

The tendinous chords of the tricuspid valve are the predominant type of connection between the papillary muscles and the tricuspid valve. Studies describing the evolutionary line of these connections are well known. The flexibility of particular leaflets of the tricuspid valve varies, as does the tension of the blood stream in particular cusps. The present study was performed on a group of 96 formalin-fixed adult human hearts, which ranged in age from 18 to 90 years and gave no evidence of congenital malformations or pathological changes. The valves were divided into five types according to earlier studies and analysis was made in terms of these types. The tendinous chords and their ramifications were counted. The surfaces of particular leaflets were measured. The ratio of marginal to ventricular leaflets was counted for each type of leaflet in particular types of valves. The parts of the main leaflets supported by specific papillary muscles were counted for types 1, 2 and 3. The number of tendinous chords decreased in leaflets in particular types of tricuspid valve, but the ratio of chords attached to the margins and ventricular surfaces was similar. The number of chords for the surface of leaflets (measured in mm2) was similar in particular types of valve for all cusps. The most differentiated were commissural chords in all types of valve. The ratio of chords attached to the margins and ventricular surfaces does not depend on the surface area of the leaflets.

Assessment of the maximum voltage-guided technique for cavotricuspid isthmus ablation during ongoing atrial flutter

OBJECTIVES

We aimed to test the maximum voltage-guided cavotricuspid isthmus (CTI) ablation technique during ongoing atrial flutter.

BACKGROUND

Former pathological and electrophysiological studies clarified that the cavotricuspid isthmus is composed of distinct muscular bundles, which are responsible for the conduction of electrical activation. Based on this observation, a maximum voltage-guided ablation technique (MVGT) was developed. This technique was assessed during pacing from the coronary sinus and was reported to be a feasible method to reach bidirectional isthmus block without the need for a complete anatomic ablation line.

METHODS

This was a prospective, randomized single center study. Twenty patients underwent CTI ablation during atrial flutter. In group I (10 pts) CTI ablation was performed with complete anatomical ablation line. In group II (10 pts) ablation was guided by the highest amplitude potentials on the CTI sequentially until bidirectional isthmus block was reached. The following parameters were compared: acute success rate, procedure time, fluoroscopy time, number of radiofrequency (RF) applications and total RF duration.

RESULTS

In all patients, atrial flutter terminated during ablation. Bidirectional isthmus block could be achieved in all pts. Procedure time was shorter in group II (107 +/- 40 vs 68 +/- 19 min, p < 0.01). Significantly less fluoroscopy was used in group II (22.6 +/- 10.6 vs 12.1 +/- 3.8 min, p < 0.01). There were less RF applications in group II (27.1 +/- 21.5 vs 5.9 +/- 2.4, p < 0.001).

CONCLUSIONS

(1) The major finding of this study is that MVGT is a feasible method even during ongoing atrial flutter. (2) Our data confirm that MVGT is an effective technique for CTI ablation with considerable decrease in procedure and fluoroscopy times.

Normal offset of the tricuspid septal leaflet in Thai fetuses

OBJECTIVE

To quantify the correlation between gestational age and the normal distance between the insertion of the medial leaflets of the mitral valve and tricuspid valve in Thai fetuses.

MATERIAL AND METHOD

A prospective study was constructed using an apical 4-chamber view at end diastole to measure the mitral valve-tricuspid valve distance (MTD) in 169 confirmed-dated singleton normal fetuses between 18 and 40 weeks of gestation at King Chulalongkorn Memorial Hospital from August 2005 to July 2006. The recorded distances were plotted against gestational ages. The 5th, 50th, and 95th centile of MTD were calculated and the relationship between MTD and gestational age was determined with regression model. One hundred and forty-seven measurements were validated for analyses.

RESULTS

Regression analysis demonstrated a linear correlation of MTD with gestational age with each increase of 1 week in gestational age, there was an increase of 0.12 mm of MTD (p <. 001). The linear regression curve that correlated MTD with gestational age showed a gradual slope (r = 0.84; p < 0.001). The MTD range from 1.3 to 5.1 mm (mean +/- SD = 2.6 +/- 0.9). A significant difference in MTD was noted on comparing to the data in Western study. Intra-observer reliability was 0.92.

CONCLUSION

The present findings support the positive correlation between MTD and advancing gestational age. However, clinically significant differences of MTD between the presented population and Caucasian fetuses underline the need for employing a locally derived data on assigning the fetal cardiac abnormality.

Pulmonary Atresia With Intact Ventricular Septum: Limitations of Catheter-Based Intervention

BACKGROUND

Pulmonary atresia with intact ventricular septum (PAIVS) has a wide spectrum of anatomic heterogeneity and invokes a wide variety of treatment strategies. We reviewed the outcome of our patients with PAIVS in order to delineate strategies for the optimal management of PAIVS. In particular, the possibility of avoiding neonatal surgical intervention with catheter-based technology was assessed.

METHODS

The study cohort was composed of all patients presented with PAIVS from January 1999 through December 2005. Demographic and anatomic variables were analyzed to determine association with in-hospital mortality.

RESULTS

Forty-four infants with PAIVS underwent catheter valvuloplasty (n = 17) and (or) surgical intervention (n = 42). The mean age and weight of the infants was six days and 3.1 kg, and the average follow-up was 40 +/- 29.5 months. Five (11%) had right ventricle dependent coronary circulation (RVDCC) and six (14%) had Ebstein's anomaly. Five (11%) patients died. Of those who underwent catheter valvotomy, three (18%) underwent shunt placement, 12 (71%) underwent right ventricular outflow tract reconstruction with shunt placement, and only two (12%) did not require a further surgical intervention in the newborn period. Multivariable analyses demonstrated RVDCC (odds ratio 21.3, p = 0.025) and Ebstein's anomaly (odds ratio 16.0, p = 0.038) to be risk factors for in-hospital mortality. Of those patients with Ebstein's anomaly, a single ventricle approach had a better outcome.

CONCLUSIONS

We demonstrated excellent recent outcomes for patients with PAIVS. Catheter-based interventions rarely avoid surgical repair. The RVDCC and Ebstein's anomaly were associated with high mortality. In patients with Ebstein's anomaly, single ventricular pathway may be the better strategy for this specific patient population.

Assessment of normal tricuspid valve anatomy in adults by real-time three-dimensional echocardiography

Background

The tricuspid valve (TV) is a complex structure. Unlike the aortic and mitral valve it is not possible to visualize all TV leaflets simultaneously in one cross-sectional view by standard two-dimensional echocardiography (2DE) either transthoracic or transesophageal due to the position of TV in the far field.

Aim

Quantitative and qualitative assessment of the normal TV using real-time 3-dimensional echocardiography (RT3DE).

Methods

RT3DE was performed for 100 normal adults (mean age 30 ± 9 years, 65% males). RT3DE visualization was evaluated by 4-point score (1: not visualized, 2: inadequate, 3: sufficient, and 4: excellent). Measurements included TV annulus diameters (TAD), TV area (TVA), and commissural width.

Results

In 90% of patients with good 2DE image quality, it was possible to analyse TV anatomy by RT3DE. A detailed anatomical structure including unique description and measurement of tricuspid annulus shape and size, TV leaflets shape, and mobility, and TV commissural width were obtained in majority of patients. Identification of each TV leaflet as seen in the routine 2DE views was obtained.

Conclusion

RT3DE of the TV is feasible in a large number of patients. RT3DE may add to functional 2DE data in description of TV anatomy and providing highly reproducible and actual reality (anatomical and functional) measurements.

Value of assessment of tricuspid annulus: real-time three-dimensional echocardiography and magnetic resonance imaging

Aim

To detect the accuracy of real-time three-dimensional echocardiography (RT3DE) and two-dimensional echocardiography (2DE) for tricuspid annulus (TA) assessment compared with magnetic resonance imaging (MRI).

Methods

Thirty patients (mean age 34 ± 13 years, 60% males) in sinus rhythm were examined by MRI, RT3DE, and 2DE for TA assessment. End-diastolic and end-systolic TA diameter (TAD) and TA fractional shortening (TAFS) were measured by RT3DE, 2DE, and MRI. End-diastolic and end-systolic TA area (TAA) and TA fractional area changes (TAFAC) were measured by RT3DE and MRI. End-diastolic and end-systolic right ventricular (RV) volumes and ejection fraction (RV-EF) were measured by MRI.

Results

The TA was clearly delineated in all patients and visualized as an oval-shaped by RT3DE and MRI. There was a good correlation between TAD_MRI and TAD_3D (r = 0.75, P = 0.001), while TAD_2D was fairly correlated with TAD_3D and TAD_MRI (r = 0.5, P = 0.01 for both). There were no significant differences between RT3DE and MRI in TAD, TAA, TAFS, and TAFAC measurements, while TAD_2D and TAFS_2D were significantly underestimated (P < 0.001). TAFS_2D was not correlated with RV-EF, while TAFS_3D and TAFAC_3D were fairly correlated with RV-EF (r = 0.49, P = 0.01, and r = 0.47, P = 0.02 respectively).

Conclusion

RT3DE helps in accurate assessment of TA comparable to MRI and may have an important implication in the TV surgical decision-making processes. RT3DE analysis of TA function could be used as a marker of RV function.

The connection between the papillary muscles and leaflets of the tricuspid valve

The tricuspid valve is more differentiated during evolutionary development than the mitral valve. In birds it is a muscular structure joined directly to the papillary muscles, although the mitral valve of birds resembles that of mammals. There have been well-known studies describing the evolutionary line of connection of the tricuspid valve with the papillary muscles. The present study was performed on a group of 107 formalin-fixed adult human hearts. The valves and papillary muscles were classified according to a scheme for human hearts drawn up earlier. The types of connection between leaflets of the tricuspid valve and the papillary muscles were classified according to a scheme drawn up earlier for vertebrates. We observed 3 types of connection between leaflets of the tricuspid valve and the papillary muscles in the group studied. The muscular and membranous connections were not linked with any one type of tricuspid valve. Atypical forms of distribution of the tendinous chords of the right ventricle were observed. It was found that valves with a higher number of leaflets were (with the exception of type 0) provided with a smaller number of tendinous chords. Atavistic features and atypical forms of distribution of the tendinous chords are present in a small percentage of samples of the human right valvular apparatus.

Anatomy and echocardiography of the normal and abnormal tricuspid valve

Perhaps because it guards the inlet to the lesser circulation, the morphologically tricuspid valve has received less attention in terms of its anatomy than the well-explored mitral valve, which will receive attention in a subsequent review in this supplement.1 As we will show in our initial review, nonetheless, the approach to morphological analysis is the same for both valves, irrespective of whether the specific morphology is displayed in the autopsy room or the echocardiographic laboratory. It is essential that the valve be analysed so as to reveal the precise structure of each if its components – the so-called valvar complex.2 Equally important, in the current era, with the burgeoning use of three-dimensional displays that place the heart firmly within the context of the body, it is essential that the components of the valve be described as seen relative to the bodily axis,3 rather than following the present custom of describing the heart as though it is removed from the body and positioned on its own apex.

The morphology of the right atrioventricular valve in the adult human heart

Studies of the morphometry and normal anatomy of the tricuspid valve are in constant demand. Knowledge of the morphology of the normal tricuspid valve may be useful, for example in the context of the transfer of a leaflet of the tricuspid valve for repair or insufficiency of the mitral valve, in repair of the tricuspid valve after blunt chest trauma and in other surgical techniques of this region. In this study, performed in a group of 107 formalin-fixed adult human hearts, we attempted to assess the form and number of the main and accessory cusps in the tricuspid valve. Rare anatomical variants of the tricuspid valve were found. Using a planimeter we evaluated the surface area of the tricuspid valve and particular leaflets. With the help of a Vernier scale we measured the length and height of individual leaflets of the tricuspid valve and the length of the commissures. No differences were found between the length of the anterior and septal leaflets. The posterior leaflet was the shortest, while the anterior leaflet was the widest and had the largest surface area. The posterior leaflet was wider than the septal leaflet and had the smallest surface area. No differences were found between the main and accessory leaflets in the length of the commissures.

Functional terminology for the tricuspid valve

BACKGROUND AND AIM OF THE STUDY

Advances in echocardiography have awoken new interest in the tricuspid valve, which otherwise has been largely ignored by cardiologists and surgeons. These advances demand a precise terminology for the description of the tricuspid valve's different anatomic structures in health and disease. While simple nomenclatures have been developed for the mitral valve, no such system has been described for the tricuspid valve.

METHODS

In order to develop a tricuspid valve terminology similar to the existing mitral valve nomenclature, a study of 50 porcine hearts was conducted. The study was designed not as a strict anatomical description but rather as a search for common parameters between both valves. The findings were based on the traditional understanding that the tricuspid valve has three main leaflets and three papillary muscles. The leaflets were defined according to their heights (free edge to base) and their chordal insertions. The papillary muscles were grouped according to the distribution of their chords to a commissure and its contiguous main leaflets.

RESULTS

In all hearts, three main leaflets were found: septal (S), anterior (A), and posterior (P), associated with a variable number of commissural leaflets (C). Three groups of papillary muscles could be identified: anteroseptal with a mean of 1.78 muscles (range: 1-4), anteroposterior with 1.08 muscles (range: 1-4), and posteroseptal with 2.42 muscles (range: 1-5). Each group was identified (counterclockwise) with the numerals 1 (anteroseptal), 2 (posteroseptal), and 3 (anteroposterior). Each half of the leaflets and their corresponding commissures were identified by the initial letter of their classic name (S, A, P, or C) and their supporting papillary muscle group (1, 2, or 3).

CONCLUSION

This system provides a method for reporting echocardiographic and surgical findings for the tricuspid valve. The system parallels previously described mitral valve nomenclature. This unified terminology should facilitate the precise recording of echocardiographic and surgical data.

Dimensions of the triangle of Koch

Dimensions of the triangle of Koch varied among the patients. The aim of this study was to present the dimensions of the triangle, and to compare the data obtained directly by post mortal measurement, using two different methods, and indirectly using mathematic formulas. The examination was performed in two independent groups consisting of 50 specimens each. Results showed that the mean value of area of the triangle of Koch obtained by the first type of post mortal measurement was significantly different from the mean value obtained using mathematic formulas (261.65 +/- 52.30 mm2 vs 116.74 +/- 13.20 mm2; p=0.00; p<0.05). But the mean value of the second type of the measurement was very similar to the mathematically obtained data (126.33 +/- 23.71 mm2 vs 116.74 +/- 13.20 mm2; p=0.278; p>0.05) (Fig. 1, Ref. 10).

Insight Into Normal Mitral and Tricuspid Annular Dynamics in Pediatrics: A Real-time Three-dimensional Echocardiographic Study

BACKGROUND

Although there are animal or adult studies analyzing annular motion of the mitral valve (MV) or tricuspid valve (TV) separately, there are no data analyzing interaction between the MV and TV, or data from the pediatric population.

METHODS

A total of 17 healthy children (age 3-15 years) were enrolled in this study. Using real-time 3-dimensional echocardiography, annular area, perimeter, segmental diameter, and bending angle were obtained and analyzed.

RESULTS

MV area increased during systole, in contrast to TV area, which decreased. TV area demonstrated a greater reduction of lateral diameter during systole. Bending motion became most acute in early diastole, which was greater for the TV.

CONCLUSIONS

MV area change differs from adults, which may be explained by a more compliant myocardium in children. Greater lateral forces on TV prevent it from becoming circular, thus, preserving valve competency. Both valves show a bending motion, which becomes most prominent during isovolumic relaxation continuing into early diastole for the TV, suggesting a relationship with torsional forces within the ventricles.

Intracardiac echocardiography: gross anatomy and magnetic resonance correlations and validations

PURPOSE

The feasibility and safety of intracardiac echocardiography (ICE) in humans, using low frequency transducers, and its excellent tissue contrast capabilities that enhances the differentiation of intracardiac structures have been previously demonstrated. However, correlations among ICE imaging and anatomic sections or magnetic resonance (MR) scan planes have never been described before. This study was designed to correlate a simplified ICE approach with the anatomy of the right atrium and great vessels obtained by serial post-mortem sections and cardiac MR images.

METHODS

A stepwise approach to ICE, which is based on our experience on over 300 consecutive patients with interatrial communications, has been correlated with anatomic sections from pressure-perfused-fixed hearts and spin echo cardiac MR imaging. A 9F-9 MHz mechanical device was used to record four transverse and one longitudinal sections for an extensive evaluation of the intracardiac architecture.

RESULTS

ICE transverse and longitudinal views allowed the detection of all the required information. Moreover, the anatomic sections and cardiac MR scan planes allowed validation of all the structures imaged by ICE. The potential clinical applications of the ICE technique are further discussed.

CONCLUSION

This paper demonstrates the basic accuracy of this new imaging modality. Therefore, mechanical ICE might be considered an active investment in cardiac catheterization laboratories, specifically in the percutaneous interventional procedure setting, discovering a new route (let's see and treat) to sophisticated interventions. In this respect, there can be little doubt that the knowledge of cross-sectional mechanical ICE imaging provides the basis for understanding the heart anatomy.

Unusual anatomical features of the right atrioventricular valve

Despite the great interest taken in the tricuspid valve, the anatomical literature on the subject still leaves much open to question. The aim of this study was to describe the natural foramina which are present in the leaflets of the tricuspid valve, as well as, well -- founded onto -- and phylogenetically lack of continuity of its attachment and the frenula of the tricuspid valve. We studied the frequency of occurrence and morphology of these features of the tricuspid valve in 107 adult hearts.

The Inferior Right Atrial Isthmus: Further Architectural Insights for Current and Coming Ablation Technologies

BACKGROUND

Although linear ablation of the right atrial isthmus in patients with isthmus-dependent atrial flutter can be highly successful, recurrences and complications occur in some patients. Our study provides further morphological details for a better understanding of the structure of the isthmus.

METHODS AND RESULTS

We examined the isthmic area in 30 heart specimens by dissection, histology, and scanning electron microscopy. This area was bordered anteriorly by the hinge of the tricuspid valve and posteriorly by the orifice of the inferior caval vein. With the heart in attitudinal orientation, we identified and measured the lengths of three levels of isthmus: paraseptal (24 +/- 4 mm), central (19 +/- 4 mm), and inferolateral (30 +/- 3 mm). Comparing the three levels, the central isthmus had the thinnest muscular wall and the paraseptal isthmus the thickest wall. At all three levels, the anterior part was consistently muscular whereas the posterior part was composed of mainly fibro-fatty tissue in 63% of hearts. The right coronary artery was less than 4 mm from the endocardial surface of the inferolateral isthmus in 47% of hearts. Inferior extensions of the atrioventricular node were present in the paraseptal isthmus in 10% of hearts, at 1-3 mm from the endocardial surface.

CONCLUSIONS

The thinner wall and shorter length of the central isthmus together with its distance from the right coronary artery, and nonassociation with the atrioventricular node or its arterial supply, should make it the preferred site for linear radiofrequency ablation.

Notes on the morphology of the tricuspid valve in the adult human heart

Rapid progress in the field of interventional cardiology has caused research in the field of morphometry of the heart to be in constant demand. In this study, performed on a group of 75 adult human hearts, the authors have attempted to assess the form and number of the main and accessory cusps in the tricuspid valve. We have classified particular forms into 8 groups, depending on the number of cusps and we have divided the cusps into 3 main groups, depending on the support of the chordae tendineae.

Sonometric study of the normal tricuspid valve annulus in sheep

BACKGROUND AND AIM OF THE STUDY

Mitral valve dynamic changes during the cardiac cycle have been previously studied in sheep using sonomicrometry. The study aim was to analyze geometric changes of the normal tricuspid annulus in sheep using a similar methodology. This is most likely the first tricuspid valve study using high temporal resolution (200 Hz = 200 data points per second).

METHODS

Thirteen crystals were implanted in seven sheep along the annulus (n = 6), at the tips of papillary muscles (n = 3), at the free edge of the leaflets (n = 3), and at the apex of the left ventricle (n = 1). Recordings (10 s) of crystal distances were used to create a three-dimensional (3D) coordinate system based on the least-squares plane of the annulus, and maximum and minimum values were calculated for length, area, and position in xyz coordinates.

RESULTS

During the cardiac cycle, the tricuspid annulus area expanded 28.6 +/- 3.6% with similar maximum expansions of each segment along the annulus: septal (10.4 +/- 1.2%), anterior (13.0 +/- 1.5%), and posterior (14.0 +/- 1.6%). The annulus was saddle-shaped, with a circumferential expansion from elliptical at minimum area to more circular at maximum area. The time delay to maximum leaflet area and maximum papillary area occurred 83 +/- 13 ms and 279 +/- 30 ms respectively after maximum annulus area.

CONCLUSION

The tricuspid valve undergoes continual and complex geometric changes during the cardiac cycle. In addition, the annulus expands significantly due to similar increases in length of the septal and free wall segments. The annulus is not in a single plane, but is saddle-shaped. The expansion and contraction of the tricuspid valve complex is stepwise, and sequential from base to apex.

Phased-array intracardiac echocardiography for defining cavotricuspid isthmus anatomy during radiofrequency ablation of typical atrial flutter

INTRODUCTION

Cavotricuspid isthmus (CTI) topography includes ridges, pouches, recesses, and trabeculations. These features may limit the success of radiofrequency ablation (RFA) of typical atrial flutter (AFL). The aim of this study was to assess the utility of phased-array intracardiac echocardiography (ICE) for imaging the CTI and monitoring RFA of AFL.

METHODS AND RESULTS

Fifteen patients (mean age 64 +/- 9 years) underwent ICE assessment (imaging frequency 7.5-10 MHz) before and after RFA of AFL. The ICE catheter was positioned at the inferior vena cava-right atrial junction and the following parameters were measured: (1) CTI length from the tricuspid valve to the eustachian ridge; (2) extent of CTI pouching; and (3) thickness pre/post RFA of the anterior, mid, and posterior CTI. CTI length was 35 +/- 6 mm at end-ventricular systole but shorter (30 +/- 6 mm) and more pouched at end-ventricular diastole (P = 0.02). A pouch or recess was seen in 11 of 15 patients (mean depth 6 +/- 2 mm). The septal CTI was more pouched than the lateral CTI, but the latter had more prominent trabeculations. Trabeculations were seen in 10 of 15 patients, and at these locations the CTI was 4.6 +/- 1 mm thick. Anterior, mid, and posterior CTI thickness pre-RFA was 4.1 +/- 0.8, 3.3 +/- 0.5, and 2.7 +/- 0.9 mm, respectively (P < 0.001 by analysis of variance). ICE guided RFA away from unfavorable CTI features (recesses/thick trabeculations). RFA applications created discrete CTI lesions that coalesced, forming diffuse CTI swelling. Post-RFA thickness was as follows: anterior 4.8 +/- 0.8 mm (P = NS vs pre); mid 3.8 +/- 0.8 mm (P = 0.05 vs pre); and posterior 3.8 +/- 0.8 mm (P = 0.02 vs pre).

CONCLUSION

Phased-array ICE permits novel real-time CTI imaging with excellent endocardial resolution and may facilitate RFA of AFL.

Diameters of the cavo-sinus-tricuspid area in relation to type I atrial flutter

Cardiac arrhythmias have troubled patients and fascinated physicians for centuries. The twentieth century was an era of progress, when the mechanism of cardiac disorders became more commonly recognised. Arrhythmias may be due to abnormalities of automaticity, to abnormalities of conduction, or to a combination of both. In order for re-entry to occur, an area of slowing conduction combined with unidirectional block must be present. Much investigation has centred on the underlying re-entry mechanisms of atrial flutter. In the light of these facts, it would seem that a close acquaintance with the detailed topography of the vena cava orifice (cavo), coronary sinus orifice (sinus) and the attachment of the septal leaflet of the tricuspid valve (tricupid) area could be of great interest, especially for invasive cardiologists. The research was conducted carried out on material consisting of 41 hearts of humans of both sexes from the age of 12 to 80 (6 female, 35 male). Classical macroscopic methods of anatomical evaluation were used. The following measurements were made: the shortest distance between the Eustachian valve and the attachment of the tricuspid valve on the left margin of the coronary sinus orifice (diameter 1), the distance between the attachment of the tricuspid valve and the inferior margin of the sinus orifice (diameter 2), the distance between the Eustachian valve and the attachment of the tricuspid valve on the right margin of the coronary sinus orifice (diameter 3), the distance between the inferior margin of the vena cava inferior and the attachment of the tricuspid valve (diameter 4) and, finally, the diameter between the attachment of the septal cusp of the tricuspid valve and the extemal border of the vena cava inferior (diameter 5). No correlation was found between the age and sex of the three groups of the material. The dimensions of the structure examined were similar in the three groups of hearts. In young adult hearts all the diameters measured ranged from 4 to 47 mm. The average diameters were, respectively: 15.02 mm (diameter 1), 8.97 mm (diameter 2), 17.27 mm (diameter 3), 26.87 mm (diameter 4), 36.42 mm (diameter 5). In the mature adult hearts all the diameters measured ranged from 8 to 45 mm; 18.19 mm (diameter 1), 10.54 mm (diameter 2), 19.95 mm (diameter 3), 28.90 mm (diameter 4), 39.63 mm (diameter 5). In the older adults hearts all the diameters measured ranged from 4 to 47 mm. The average diameters were, respectively: 15.65 mm (diameter 1), 8.70 mm (diameter 2), 7.25 mm (diameter 3), 26.80 mm (diameter 4), 35.85 mm (diameter 5). On the basis of our study we were able to conclude that the diameters of the cavo-sinus-tricuspid area were constant and did not differ significantly within the three (young, mature, old) adult groups examined.

Provision of tricuspid valve leaflets by septal papillary muscles in the right ventricle of human and other mammal hearts

Leaflets of the tricuspid valve are provided by tendinous cords extending from the papillary muscles. The situation is complicated with the septal muscles, which generally occur in two groups, one as constant musculus coni arteriosi and the second as other variable septal muscles. We tested whether there is a variability in the provision of the tricuspid valve in different taxonomical groups of mammals. The material examined consisted of 299 hearts of mammals (Primates, Ungulata, Carnivora, Lagomorpha, Rodentia, Marsupialia). The musculus coni arteriosi in the majority of mammals provided only the front leaflet, but among Ungulata and Rodentia it provided simultaneously the front and septal leaflet. The other septal muscles provided the front, septal and even back leaflets. The following regularity was observed: in the hearts of Primates provision of the front leaflet and the front part of the septal leaflet predominated, among Ungulata the muscles provided the middle part of the septal leaflet, but among the other mammals the rest of the septal muscles provided, significantly, the back part of the septal leaflet. Such a provision was characteristic for predators, hares, rodents and marsupials. These circumstances may allow the conclusion to be drawn that there is a taxonomical dependence in the provision of the tricuspid valve in the hearts of the mammals under examination.

Randomized comparison of anatomic and electrogram mapping approaches to ablation of typical atrial flutter

INTRODUCTION

The cavotricuspid isthmus can be ablated using an anatomic approach or an electrogram mapping approach in which sites at which there is a gap in the line of block are targeted. The aim of this study was to compare the anatomic and electrogram mapping approaches for creating a line of block in the cavotricuspid isthmus after an initial, unsuccessful anatomically directed ablation line.

METHODS AND RESULTS

The subjects of this study were 63 patients with isthmus-dependent atrial flutter in whom a single series of contiguous applications of radiofrequency energy guided by fluoroscopy in the cavotricuspid isthmus did not result in complete block. The patients were randomly assigned to additional ablation on an anatomic basis (n = 31) or guided by single potentials or narrowly split double potentials during coronary sinus pacing (n = 32). After every 15 applications of radiofrequency energy, the alternate approach was used until complete block was achieved. Before cross-over, complete block was achieved in 6 patients (19%) with the anatomic approach compared with 19 patients (59%) with the electrogram mapping approach (P < 0.005). The electrogram mapping approach also was more effective than the anatomic approach in achieving complete isthmus block after the first cross-over (72% vs 23%, P < 0.005) and after the second cross-over (80% vs 42%, P < 0.05).

CONCLUSION

When there is incomplete block after an initial series of applications of radiofrequency energy in the cavotricuspid isthmus, complete block is achieved more efficiently with an electrogram mapping approach than with an anatomic approach.

Deviation of atrial septum primum in association with normal left atrioventricular valve size

Deviation of atrial septum primum (DASP) is an unusual anatomic finding in patients with normal left atrioventricular valve size. To better describe this anomaly, we reviewed our echocardiographic database from January 1987 to May 1999. Twenty-four patients had DASP and a normal-sized left atrioventricular valve. Six had inferior DASP with common atrioventricular canal. Of these, 3 had evidence of left atrial outlet obstruction. Five survived surgical intervention with follow-up of 24 +/- 14 months. Seventeen patients had superoposterior deviation with the right pulmonary veins draining anomalously to the right atrium. Only 8 of 17 underwent surgical resection; none of the 17 have evidence for late development of obstruction. One patient had both inferior deviation and superoposterior DASP and underwent early successful repair. DASP occurs in patients with normal left atrioventricular valve size. Inferior DASP can result in left atrial outlet obstruction and requires surgical intervention. Superoposterior DASP carries less physiologic consequence. Echocardiography can distinguish this anomaly from other forms of left atrial obstruction.

Anatomic study of the tricuspid valve in children

We performed an anatomic study of the right atrioventricular valve in children under one year of age using a conservative method of dissection of the heart valve. The main aspects studied were the number of cusps and their morphometric characteristics, such as the width of the base and the depth of the cusps. Other parameters studied were the number of papillary muscles, number of tendinous cords, and diameter of the fibrous ring and the last one were divided in three regions, anterior, posterior and septal for localization of cusps. Our results showed that the number of cusps varied from two to four. Three cusps was the commonest finding and the fourth cusp, if present, was classified as anterolateral in location. The anterior and septal cusps had bases bigger than those of the posterior and anterolateral cusps; the septal cusp was deeper than the others; and the number of tendinous cords was greater for the anterior and septal cusps than for the posterior and anterolateral cusps. In addition, the posterior region showed great variability: in 35.7% it was occupied by undeveloped valve tissue and the posterior valve in these cases was located anteriorly.

How constant anatomically is the tendon of Todaro as a marker for the triangle of Koch?

INTRODUCTION

Although well recognized by anatomists as a border of the triangle of Koch demarcating the location of the AV node, the tendon of Todaro is not visible in the operating room or in the catheterization laboratory. Instead, clinicians use as surrogate a projected line between the eustachian valve and the central fibrous body. The constancy of the tendon of Todaro within this border remains to be determined.

MATERIALS AND RESULTS

We reexamined serial histologic sections from 25 adults and 50 infants and gross dissections in four normal hearts. The tendon of Todaro was identified in all cases and traced to the central fibrous body in all but one case. It tended to be thicker in the hearts of infants cases (0.2 to 0.8 mm vs 0.1 to 0.6 mm). The tendon and the hinge-line of the septal leaflet of the tricuspid valve were consistent as landmarks for location of the compact AV node in all the cases studied by histology. Gross dissections traced the tendon to the free edge of the eustachian valve.

CONCLUSION

The tendon of Todaro is present in hearts obtained from both adults and infants. It, or its surrogate, is a reliable border for the triangle of Koch and serves as a landmark to location of the atrial components of the AV conduction axis.

Hemitricuspid dysplasia in association with ventricular septal defect

The tricuspid valve essentially consists of a straight septal leaflet and a curved mural leaflet that includes the anterior and posterior leaflets. A plane bisecting the septal and anterior leaflets divides the chordopapillary support of the tricuspid valve into 2 groups. One group is related to the bulbar and adjacent perimembranous and sinus components of the interventricular septum. The other is related to the trabecular septum and the adjacent free wall. We report our surgical findings in 5 patients who had dysplasia of the leaflets and chordopapillary support related to the bulbar, perimembranous, and sinus portions of the interventricular septum, in conjunction with a perimembranous ventricular septal defect. Phylogenic, ontogenic, and surgical implications of this association are discussed.

Living anatomy of the atrioventricular junctions. A guide to electrophysiologic mapping. A Consensus Statement from the Cardiac Nomenclature Study Group, Working Group of Arrhythmias, European Society of Cardiology, and the Task Force on Cardiac Nomenclature from NASPE

Current nomenclature for the atrioventricular (AV) junctions derives from a surgically distorted view, placing the valvar rings and the triangle of Koch in a single plane with antero-posterior and right-left lateral coordinates. Within this convention, the aorta is considered to occupy an anterior position, although the mouth of the coronary sinus is shown as being posterior. Although this nomenclature has served its purpose for the description and treatment of arrhythmias dependent on accessory pathways and atrioventricular nodal reentry, it is less than satisfactory for the description of atrial and ventricular mapping. To correct these deficiencies, a consensus document has been prepared by experts from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. It proposes a new anatomically sound nomenclature that will be applicable to all chambers of the heart. In this report, we discuss its value for description of the AV junctions, establishing the principles of this new nomenclature.

The architecture of the atrial musculature between the orifice of the inferior caval vein and the tricuspid valve: the anatomy of the isthmus

INTRODUCTION

Electrophysiologists recognize a so-called "isthmus" in the right atrium through which passes the reentrant circuit of common atrial flutter. Ablative lesions placed in this narrow channel have proved effective in breaking the circuit. To the best of our knowledge, however, no study has been performed to establish the arrangement and orientation of the atrial myocardial fibers in this crucial area.

METHODS AND RESULTS

We examined 28 normal heart specimens, identifying a quadrilateral area composed of three morphologic sectors between the inferior caval vein and the tricuspid valve confluent superiorly with the triangle of Koch. Within this quadrilateral, there are constant recesses, or sinuses, inferior and lateral to the orifice of the coronary sinus. The inferior isthmus measured an average of 31+/-4 mm (range 19 to 40). Gross examination identified marked differences in the atrial wall forming the quadrilateral. A smooth anterior component forming the vestibule of the tricuspid valve was found in all the hearts, but variations in the remaining sectors were seen in ten specimens. The usually membranous posterior sector was noticeably muscular in three specimens, while the middle, trabecular sector was more membranous in five specimens. We demonstrated the orientation of the subendocardial atrial fibers by dissection in 14 specimens, revealing a relatively constant overall pattern in eight specimens and variations in fiber orientation in the remaining specimens.

CONCLUSION

There are considerable anatomic variations in the atrial wall that comprises the so-called isthmus. The presence of recesses and membranous areas in some hearts and the variations in arrangement of the subendocardial fibers are relevant in improving understanding of conduction in this area.