Br Heart J: first published as 10.1136/hrt.36.10.971 on 1 October 1974. Downloaded from British Heart journal, I974, 36, 97I-980. Electrophysiology of ventricular inversion' Paul C. Gillette, Milton J. Reitman, Charles E. Mullins, Robert L. Williams, John T. Dawson, Jr., and Dan G. McNamara From The Section of Cardiology, Department of Pediatrics, Baylor College of Medicine, and Texas Children's Hospital, Houston, Texas, U.S.A. Electrophysiological studies were carried out in 7 subjects with angiographically proven ventricular inversion in order to determine if this technique could be used in the study of arrhythmias in such subjects. Three sub- jects with normal PR intervals on the electrocardiogram had normal low right atrium to His (LRA-H) and His to ventricle (HV) intervals at rest. With atrial pacing, I of these 3 with normal PR interval developed Mobitz II second-degree atrioventricular block. Of 2 subjects with first-degree atrioventricular block r was found to have prolonged LRA-H and HV intervals, and the other had only LRA-H prolongation. In both subjects with complete atrioventricular block, the block was below the His bundle recording site. One of these patients with complete A V block wasfound to be able to conduct through his A V conducting system during the supernormal period. This study found that useful information can be obtained by recording the His bundle potential in patients with ventricular inversion. Conduction abnormalities were found from the AV node through the His-Purkinje system. This technique may be useful in making clinical decisions in patients with ventricular inversion and complex arrhythmias. Ventricular inversion with a laevo-transposition of system as well as other anomalies in the structure http://heart.bmj.com/ the great arteries usually occurs with one or more and course of the AV node, His bundle, and bundle- intracardiac anomalies and in 30 to 6o per cent of branches (Lev, Licata, and May, I963; Hudson, the cases, an atrioventricular conduction disturb- I970). Wolff, Freed, and Ellison (1973) have reported ance is present at birth or develops later (Walker success in only 2 of 8 patients with ventricular in- et al., I958). Complete atrioventricular block, one version in whom they attempted to record His of the frequent arrhythmias (Walker et al., I958), bundle electrograms. may be a major factor in the morbidity and mor- The purpose of this study was to evaluate the tality in these patients, sometimes necessitat- technique of His bundle recording in the study of on September 27, 2021 by guest. Protected copyright. ing an artificial pacemaker. In evaluation of atrioventricular conduction in patients with ven- patients with atrioventricular conduction disturb- tricular inversion in sinus rhythm as well as with ances from several causes, the bundle of His electro- partial and complete AV block. gram has proved to be a helpful new technique (Scherlag et al., i969; Brodsky et al., I97I; Damato Subjects and methods et al., 1969; Roberts and Olley, I972). Since the The His bundle potential was recorded in 7 patients arrhythmias of patients with ventricular inversion with ventricular inversion during diagnostic cardiac are frequently complex, it seems likely that record- catheterization, using the percutaneous sheath femoral ings of His bundle potentials would be helpful in vein approach. The patients were sedated with meperi- their management. However, there is a theoretical dine, promethazine, and chlorpromazine. None was difficulty in recording and interpreting the His receiving digitalis or other cardioactive medications. Bi- bundle electrogram in patients with ventricular and tripolar electrode catheters were used with inter- inversion because of inversion of the conduction electrode distances of either 2 or IO mm. The technique was the same as that used in subjects with non-inverted Received 5 March 1974. ventricles. The tip of the catheter was positioned in the 1Supported in part by a grant from the National Institutes of apex of the right-sided morphological left ventricle and Health, United States Public Health Service, and by a withdrawn with clockwise rotation (Narula et al., I971). USPH Grant from the General Clinical Research Branch, During this withdrawal several potentials could be National Institutes of Health. sequentially recorded between the low right atrium and Br Heart J: first published as 10.1136/hrt.36.10.971 on 1 October 1974. Downloaded from 972 Gillette, Reitman, Mullins, Williams, Dawson, JYr., and McNamara ventricle potentials. As the catheter was withdrawn, the Results became closer to the low atrium middle potential right could be recorded in all 7 potential. The discrete sharp potential closest to the low The His bundle potential was the method right atrium potential was taken as the His bundle subjects in which it attempted by potential. Because of the difficulties of inserting multiple described above. No modifications in technique catheters in children, atrial placing was carried out only were necessary because of the ventricular inversion. once. His bundle pacing was not attempted. The cath- The intervals recorded for LRA-H, HV, and LB- eters were connected to a photographic recorder through V are found in the Table. an Electronics for Medicine junction box. Records were Three subjects were in sinus rhythm with normal made at I00 and 200 mm per second with 0o02 sec or I PR interval and normal QRS duration at the time of used were sec time lines. The frequency band widths electrophysiological study (Cases I, 5, and 7). In 40-50o Hz. Principles of electrical safety in the labora- them normal resting LRA-H and HV intervals tory were followed closely, since the electrode catheter re- creates a conduction of potential electrical hazard. were found (Fig. i). Case 5, who had recently All measurements were made from the first rapid covered from surgical complete atrioventricular deflection of one potential to the first rapid deflection block, was stressed by atrial pacing to a rate of 133. of the next. Three different intervals were searched for Repeatedly at this rate he developed Mobitz II and measured when possible: the low right atrium to second-degree block by suddenly dropping a beat. His (LRA-H), the His to ventricle (HV), and the mor- The block was between the His and left bundle- phological left (right-sided) bundle-branch to ventricle branch potential (Fig. 2). (LB-V). The left bundle-branch is defined as the first Two subjects in sinus rhythm showed first- division of the common bundle, which in ventricular in- version is found in the morphological left (right-sided) degree atrioventricular block at the time of study ventricle. (Cases 3 and 6). Case 3, whose surface electrocardio- Subjects ranged in age from 22 months to 29 years gram showed a complete bundle-branch block (Table). Ventricular inversion was identified by car- pattem (Fig. 3) demonstrated both LRA-H and diac catheterization and angiography, and each patient HV prolongation on his His bundle electrogram had the characteristic leftward initial deflection of the (Fig. 4). When the catheter was advanced slightly QRS complex on the transverse plane of the surface farther into the right-sided ventricle, the His electrocardiogram. Two of the subjects had congenital potential was much less well recorded, but a dis- atrioventricular block and the other were third-degree 5 crete potential could be seen after each ventricular in sinus rhythm at the time of the study. One of these 5 depolarization (Fig. 5). The second subject (Case 6) had only recently recovered from surgical third-degree http://heart.bmj.com/ atrioventricular block. Atrial pacing was carried out in with first-degree atrioventricular block had a normal this patient in order to elicit a potential atrioventricular QRS duration and showed only LRA-H prolonga- block. tion. TABLE Results of His bundle electrocardiogram study in patients with ventricular inversion Case Age Associated lesions Rhythm by QRS LRA-H HV LB-V No. (yr) electrocardiogram duration (msec) (msec) (msec) (msec) on September 27, 2021 by guest. Protected copyright. I 5 Pulmonary stenosis Sinus 8o 60 45 25 2 I ° Left-sided AV valve Complete atrio- regurgitation ventricular block go I50 Blocked 20 3 I8 Double inlet left ventricle, Sinus, first-degree pulmonary stenosis, post- atrioventricular operative Blalock-Taussig block I20 150 I00 Not shunt recorded 4 29 Ventricular septal defect, Complete atrio- pulmonary stenosis ventricular block go 120 Blocked Not recorded 5 9 Postoperative valve and Sinus subvalvar pulmonary stenosis 70 80 50 20 6 14 Ventricular septal defect, Sinus, first-degree valvar and subvalvar atrioventricular pulmonary stenosis block 8o I40 35 Not recorded 7 I3 Double inlet left ventricle, Sinus pulmonary stenosis 85 I00 50 30 Br Heart J: first published as 10.1136/hrt.36.10.971 on 1 October 1974. Downloaded from Electrophysiology of ventricular inversion 973 aVr t -"-,aI -%,--.Olp N. - 4. V HBE LRA LA te~~ < ~~~ M 't.%;Fw .W. .- . e-- ,-#w c8 0Omsoc FIG. I His bundle electrogram of Case I with simultaneous surface lead a VR showing normal LRA-H, HV, and LB-V intervals. During the tracing the catheter movedfarther into the ven- tricle, moving from the region of the His bundle to that of the right-sided 'left' bundle-branch. http://heart.bmj.com/ At the time of study, two subjects were felt to be mal and distal electrode pairs while the H1 was only in complete atrioventricular block (Cases 2 and 4). recorded by the proximal electrodes pair. Both had documentation of their complete atrio- ventricular block at the time of their first electro- cardiogram which was taken in the first year of life Discussion (Fig. 6). Neither had any history of Adams-Stokes His bundle studies have contributed to the funda- attacks. Both had incomplete bundle-branch block mental understanding of conduction disturbances on September 27, 2021 by guest.