Barbara Guller

The Atrioventricular Conduction System in Two Cases of Tricuspid Atresia

The morphology of the atrioventricular (A-V) conduction system was studied by serial histologic section in two cases of tricuspid atresia type IB (without transposition of the great arteries, with subpulmonary stenosis). The A-V node was adjacent to the central fibrous body, and its location was indicated by a “dimple” in the floor of the right atrium. The left bundle branches originated unusually close to the nodal-bundle junction. The right bundle branch was markedly elongated in its course to the right septal endocardium. It was situated along the inferior aspect of the channel-like ventricular septal defect as it traversed the septum. The early origin of the left bundle branches and the markedly elongated course of the right bundle branch were such that, theoretically, abnormal spread of the activation wave might result.

Morphological Studies in Tricuspid Atresia

Fourteen hearts with tricuspid atresia were reviewed at autopsy. The study included examples of normally related great arteries and of transposition of the great arteries; instances of pulmonary stenosis were present in both groups. In these examples of tricuspid atresia the size of the right ventricle depended on the size of the ventricular septal defect. The ventricular septal defect and the right ventricle usually were smaller in proportion to the size of the heart in specimens with normally related great arteries. In the absence of transposition of the great arteries, the ventricular septal defect was found to be the site of obstruction to pulmonary flow, and its size in relation to the size of the aorta determined the size of the pulmonary artery. Morphologic abnormalities exist in the region in which the proximal portions of the major atrioventricular conduction system (A-V node, bundle of His, origin of bundle branches) normally are located; thus, anatomic abnormalities in the course of the atrioventricular conduction tissue could be expected in tricuspid atresia. Based on histologic evidence, severe elevation of pulmonary vascular resistance, in general, does not occur in infancy in tricuspid atresia.

Computer analysis of changes in frank vectorcardiograms of 666 normal infants in the first 72 hours of life

Frank vectorcardiograms (VCGs) were collected on magnetic tape for 666 normal newborn infants at 1, 6, 12, 24, 36, 48, 60, and 72 hours after birth and analyzed by computers. The final total included 1,337 VCGs for white babies and 413 for blacks. No previous report has been made for the normal neonate with such a large sample, and no previous substantiation exists of possible age or sex differences at this early age. This study establishes a statistically significant change in vectorcardiographic patterns over the first three days, specifically in the measurements P duration, QRS duration, maximal spatial QRS amplitude, S in lead x, and T in lead z, as well as for several time-normalized QRS vectors. (P less than or equal to .005.) Racial differences were significant for T waves in lead z. This study supports the use of vectorcardiographic standards sensitive to the age of the newborn as well as to race.

Computer interpretation of Frank vectorcardiogram in normal newborns: Identification of right ventricular dominance patterns*

Summary Among 100 normal newborns, the right ventricular dominance pattern had a clockwise horizontal loop in 38, a figure-of-8 in 40, and a counterclockwise direction in 22. Normal values of vector angles and magnitudes recorded with a computerized Frank vectorcardiographic system differed for each type of right ventricular dominance pattern and showed less spread than usually is reported in the newborn. Thus, the vectorcardiographic criteria for right and left ventricular hypertrophy proposed in this study may allow recognition of congenital heart disease in the neonate.

Computer interpretation of Frank vectorcardiogram in normal infant: Longitudinal and cross-sectional observations from birth to 2 years of age

The evolution of the Frank vectorcardiogram (VCG) was studied from longitudinal observations (60 normal infants) and from cross-sectional observations (231 normal infants) from birth to two years of age. Age specific normal values for the Cartesian coordinates of 14 vectors including maximal QRS-T and timed vectors in the horizontal and frontal plane were determined with both methods of analysis. In longitudinally followed infants the most significant involution of right ventricular forces occurred between the newborn period and 7-14 weeks of age. These changes included disappearance of clockwise horizontal loop rotation and a leftward shift of maximal and terminal forces as well as a rightward shift of initial vectors. Longitudinal observations were useful for prediction of the normal Frank VCG in the 7 to 14-week-old infant from values observed in the newborn period and for prediction of the horizontal loop rotation throughout infancy. Cross-sectional data showed a wider range of normal values than longitudinal data in the same 7 to 14-week-old infants, but age specific normal values were well reflected between 4 and 24 months of age from cross-sectional data.

Angiocardiographic Findings in Tricuspid Atresia: Correlation with Hemodynamic and Morphologic Features

Although the general morphologic and hemodynamic features of tricuspid atresia are well established, exact angiocardiographic diagnosis of such associated conditions as pulmonary stenosis and transposition of the great arteries may be a problem. Therefore, we reviewed the angiocardiographic and hemodynamic findings in tricuspid atresia from 20 patients and from autopsies upon the hearts of 14 patients to determine the relationship of the angiocardiographic features to the morphologic and hemodynamic findings. Special attention was given to the relationship between the size of the right ventricle and the size of the ventricular septal defect (VSD), since recent morphologic studies of tricuspid atresia (1) indicate that the former measurement depends in part upon the latter. Material and Methods The records of 31 patients with tricuspid atresia seen between 1946 and 1966 were studied, and thoracic roentgenograms were available for review in 27 of them. Large-film, biplane angiocardiography was performed wit...

ETIOLOGY OF RIGHT BUNDLE BRANCH BLOCK (RBBB) FOLLOWING CLOSURE OF VENTRICULAR SEPTAL DEFECT (VSD)

Recent reports on the etiology of RBBB after closure of VSD have implied that RBBB is caused solely by the ventriculotomy and that it is absent when VSDs are repaired via the tricuspid valve; this suggests that postoperative RBB3 in VSD is primarily due to interruption of the right ventricular subendocardial Purkinje network. To answer this question, we reviewed the electrocardiograms, available vectorcardiograms, and operative notes of two groups: group 1 (38 patients with ventricular septal defects closed via the tricuspid valve) and group 2 (26 patients with isolated muscular VSD closed via ventriculotomy). Fifteen patients (37%) of group 1 and 14 (54%) of group 2 developed RBBB characterized by a delay in terminal forces in the immediate postoperative period. Initial activation was altered in the horizontal plane in 12 of the 15 patients (80%) of group 1 with RBBB and in 6 of the 14 patients (43%) in group 2 with RBBB. This difference between the groups was statistically significant (P<0.05). We assume that this alteration in initial forces results from delay in transmission through the right bundle system. These findings suggest that damage to the right bundle near the VSD (1) alters the initial phase of ventricular depolarization and (2) may also produce a delay in terminal forces--a delay that is known to occur after interruption of the subendocardial Purkinje network resulting from ventriculotomy.

Electrocardiographic diagnosis of malformations associated with tricuspid atresia: Correlation with morphologic features☆

Abstract The electrocardiographic findings in 31 cases of tricuspid atresia were reviewed. Electrocardiographic differentiation of the types of tricuspid atresia was possible to some extent, but vectorial analysis of the scalar ECGs suggests that the vectorcardiogram provides the best and easiest differentiation among the anatomic types of tricuspid atresia. Patients with transposition of the great vessels (type II) tended to have no left axis deviation (as previously reported) and a clockwise rotation of the vector loop in the frontal plane. In the precordial ECGs, left ventricular hypertrophy based on voltage criteria was absent when the great vessels were transposed. Vectorial analysis of precordial scalar ECGs showed that patients without pulmonary stenosis or atresia tended to have wide horizontal vector loops with display of anterior forces and those with pulmonary stenosis frequently had narrow horizontal loops which were oriented posteriorly. Repolarization abnormalities such as inverted or biphasic T waves in V 6 were present only in patients with increased pulmonary flow. The electrocardiographic features observed with various associated malformations of tricuspid atresia appeared to be related to the morphologic findings in these malformations.