Ehud Krongrad

Further Observations on the Etiology of the Right Bundle Branch Block Pattern Following Right Ventriculotomy

Fifteen patients with various congenital heart defects were studied during open heart surgery in order to establish the precise mechanism by which a right ventriculotomy causes a right bundle branch block (RBBB) pattern on the scalar electrocardiogram (ECG). All required a right ventriculotomy for the correction of their defects. In each, the right ventriculotomy was carried out in steps, with incisions (3 to 7) of approximately 1 cm in length. Six simultaneous scalar ECG leads were recorded prior to the first incision and following each incision. The QRS duration was then measured and related to the length of the ventriculotomy.Following the right ventriculotomy, 12 of the 15 patients developed an RBBB pattern; the remaining three did not. In all cases, the total increase in QRS duration occurred during one specific incision of the right ventricular free wall and was not related to the total length of the ventriculotomy or to the sequence of the incisions. The site at which incision of the right ventricle caused the RBBB pattern was located at between 40 to 73% of the distance between the pulmonary artery annulus and the inferior border of the heart in nine patients; in three patients the site was higher on the right ventricular free wall.Our results explain why some patients who had a right ventriculotomy during open heart surgery do not develop an RBBB pattern on the scalar ECG. Also, since no relation was found between the length of the incision and the QRS duration, our results suggest that the ventriculotomy-induced RBBB pattern is unlikely to be due to disruption of a continuous Purkinje network but is probably due to disruption of a distal branch or branches of the right bundle.

Postoperative left anterior hemiblock and right bundle branch block following repair of tetralogy of Fallot. Clinical and etiologic considerations.

Previous reports have indicated an incidence of right bundle branch block (RBBB) and left anterior hemiblock (LAH) pattern varying from 8-22% following corrective surgery in patients with tetralogy of Fallot. Among 207 patients with tetralogy of Fallot operated on at our institution, 8.7% developed an ECG pattern of RBBB and LAH. These patients were followed for 1-13 years (mean 6.2 years) for a total of 111 patient years. All patients are alive and none have had documented late atrioventricular dissociation, syncope, or other symptoms. Transient heart block was present in one patient in the immediate postoperative period but has not recurred. This group of patients differs significantly from other series in which such an ECG pattern was associated with a marked increase in morbidity and mortality. These data and the experimental evidence suggest that two distinct groups of patients exist: 1) a group in which this ECG pattern is secondary to lesions within the bundle of His and 2) a group in which the pattern is caused by lesions in the peripheral conduction system. It is postulated that these two groups which demonstrate the same ECG pattern may carry significantly different prognoses. Analysis of H-V intervals postoperatively may help identify patients at risk.

Conduction Intervals and Conduction Velocity in the Human Cardiac Conduction System Studies during Open-Heart Surgery

Specialized fiber electrograms were recorded in 64 patients during open-heart surgery. Intervals were measured from the proximal His bundle, distal His bundle, and right and left bundle branches to the earliest QRS deflection in the limb lead ECG (pH-Q, dH-Q, RB-Q, and LB-Q interval, respectively). There was an increase of pH-Q intervals with increasing age such that at age 3 months the normal range of pH-Q interval was 13-27 msec, while at 14 years of age it was 32-54 msec. For patients 15 years of age and older, the normal range of pH-Q interval was 35-54 msec, similar to that reported by several investigators using catheter technic and suggesting that most His bundle electrograms recorded by catheter technic in fact record from the proximal His bundle. The dH-Q interval varied from 18 to 35 msec, the RB-Q interval from 18 to 30 msec, and the LB-Q interval from 20 to 39 msec. These normal ranges of RB-Q and LB-Q intervals are greater than previously reported. Overlaps existed between the normal range of pH-O and dH-Q or LB-Q intervals, dH-Q and RB-Q or LB-Q intervals and, at least in children, the pH-Q and RB-Q intervals. Thus the timing of a specialized fiber electrogram does not necessarily reflect its anatomic location. AV nodal electrograms were not recorded although the recording sites included the known anatomic location of the AV node. Conduction velocity in the His bundle was determined and averaged 1.5 m/sec (range 1.3-1.7 m/sec).

Electrophysiologic Identification of the Specialized Conduction System in Corrected Transposition of the Great Arteries

Electrophysiologic identification of the specialized conduction system was performed during open-heart surgery in two cases of corrected transposition of the great arteries (1-TGA) with situs solitus, dextrocardia or dextroversion and membranous ventricular septal defect (VSD). In one case there was accompanying subvalvlar pulmonary stenosis and in the other there was an Ebstein-like deformity of the systemic atrioventricular (A-V) valve. Electrograms were recorded throughout the right atrium and morphologic left ventricle in the case with subvalvar pulmonary stenosis and throughout the left atrium and morphologic right ventricle in the case with the Ebstein-like deformity of the systemic A-V valve. Specialized conduction system electrograms were recorded exclusively at sites anterior to the membranous VSD in both cases and at no other sites in the respective atrium or ventricle studied. There was first degree A-V block in both cases and in each the site within the specialized conduction system of this delay was proximal to the specialized fiber electrogram recording sites and thus probably proximal to the bifurcation of the bundle branches. In addition, on, the Ebstein-like deformity of the systemic A-V valve present in one case was confirmed by directly recording ventricular electrograms in an area of “atrialized-ventricle above the valve.

Electrophysiological Delineation of the Specialized A-V Conduction System in Patients with Congenital Heart Disease II. Delineation of the Distal His Bundle and the Right Bundle Branch

The course of the distal His bundle and the right bundle branch was electrophysiologically delineated during open heart surgery in nine patients with tetralogy of Fallot and in six other patients with various forms of congenital heart disease. In patients with tetralogy of Fallot, right bundle branch electrograms were usually recorded up to 25 mm from the plane of the tricuspid valve annulus and only rarely beyond this site, indicating that the electrical activity in the right bundle branch was isolated from right ventricular myocardium to a site 25 mm away from the tricuspid annulus in the patients studied. In one patient with right bundle branch block pattern on the electrocardiogram induced by a ventriculotomy, the right bundle branch was traced to the Purkinje fiber-ventricular muscle junction, supporting the observation that a right bundle branch block pattern induced by ventriculotomy does not indicate that injury to the proximal part of the right bundle branch occurred.In five patients with various forms of congenital heart disease we did not record electrical activity from the distal His and right bundle branch. The anatomic and functional reasons for this failure are discussed. In one patient with a common ventricle, the identification of the specialized atrioventricular (A-V) conduction system allowed for total surgical correction of this anomaly without injury to the conduction system. The electrophysiological delineation of the specialized atrioventricular conduction system is suggested for all patients undergoing open heart surgery who have complicated congenital heart disease on which no data are available regarding the exact location of the specialized atrioventricular conduction system, for patients with unusual ventricular anatomy, and for patients in whom the hemodynamic and angiographic studies do not correlate well with the electrocardiogram.

Methods for recording electrograms of the sinoatrial node during cardiac surgery in man.

Recent reports have shown that it is possible to record extracellular electrograms from the rabbit and dog sinoatrial (SA) node. We applied similar techniques to record SA nodal activity in 23 patients who underwent cardiac surgery for various forms of heart disease. Both a bipolar technique, using pairs of electrodes at various interelectrode distances, and a unipolar technique, using an exploring and an indifferent electrode, were used. To record SA nodal electrograms, polarity was reversed from the conventional electrocardiographic recording; high amplification (100 MV/cm) and low-pass filters (0.15–30 Hz) were used.SA nodal electrograms were recorded from eight of 12 patients using the bipolar method and from nine of 11 patients using the unipolar method. There were no significant differences in the success rate or quality of the recording between the two methods. However, the unipolar method allowed a more accurate localization of the SA node.Human SA nodal electrograms resembled those of the dog and rabbit and showed two distinct slopes: a diastolic slope and an upstroke slope preceding the P wave of the ECG. SA conduction times were 32.4 ± 2.8 msec (mean ± SEM) at sinus (PP) cycle lengths of 587.6 ± 35.6 msec for the bipolar method, and 38.2 ± 3.2 msec at sinus (PP) cycle lengths of 712.2 ± 50.7 msec for the unipolar method.These methods for recording of extracellular SA nodal electrograms in man may prove useful in 1) localization of the SA node during open heart surgery and 2) assessment of SA nodal function in health and disease.

Intraoperative recording of the His bundle electrogram in man. An assessment of its precision.

To estimate the effect of distance between the electrode and the signal source on the amplitude of the His bundle electrogram (HBE) recorded during open heart surgery, a specially designed probe, containing six pairs of closely spaced (1 mm) electrodes was placed on the endocardial surface of the right atrium such that each electrode pair was parallel to the course of the His bundle. The amplitude of the HBE recorded through electrodes closest to the His bundle ranged from 0.76 to 3.44 mV, at 1 mm from 0.38 to 1.13 mV, at 2 mm from 0.27 to 0.86 mV, and at 3 mm from 0.2 to 0.44 mV. Maximal amplitude of HBE decreased by 57% at I mm, 73% at 2 mm, and 82% at 3 mm. The percent decrease was initially rapid, then declined more slowly at distances greater than 1 mm, resembling in form data obtained previously in animal studies by different techniques.Since the maximum HBE was greater than 1.0 mV in nine of 11 patients, and equal to or greater than 1.0 mV in only two of 11 patients at 1 mm, and less than 1.0 mV in all patients 2.0 mm from the maximal HBE, the anatomic location of the His bundle can be estimated from HBE amplitude. Intracardiac electrograms, recorded through closely spaced bipolar electrodes during open heart surgery, afford clinically useful precision in locating the specialized conduction tissue of the heart.

Anorexia nervosa: A cause of pericardial effusion?

SummaryEchocardiographic studies revealed the presence of pericardial effusion in 4 patients with anorexia nervosa, whose weights had fallen by 38 to 53% of their body weight at the onset of disease. Each patient had a normal or small cardiac image on chest roentgenogram. The presence of increased pericardial fluid may partially explain the decreased voltage on the electrocardiogram, and the distant heart sounds heard in some of these patients.The cause of the pericardial effusion is not clear. It may possibly occur in other diseases that produce marked weight loss and cachexia.

Pacing the Human Cardiac Conduction System During Open-heart Surgery

Specialized fiber electrograms were recorded from selected sites along the His bundle and bundle branches during open-heart surgery in 26 patients. The heart was then paced from the same recording sites. Stimuli applied to the proximal His bundle recording site always resulted in His bundle pacing, which was characterized by a stimulus artifact-to-QRS interval which equaled or very nearly equaled the previously recorded His bundle electrogram-to-QRS interval, and no change in QRS duration or waveform from that recorded with a conducted atrial beat. When stimuli were applied to distal His bundle recording sites, the response was variable: in some instances, ventricular pacing occurred; in other instances, His bundle pacing occurred; and in still other instances, ventricular pacing occurred when high stimulus amplitudes were applied, while His bundle pacing occurred when the stimulus amplitudes were reduced below a range of 0.5-3.5 ma. Stimuli applied to the right or left bundle branch recording sites always resulted in ventricular pacing. Therefore, when stimuli are applied to specialized fiber recording sites and His bundle pacing results, it is certain that the site of origin of the previously recorded specialized fiber electrogram is the His bundle, but when ventricular pacing results, the site of origin of the previously recorded specialized fiber electrogram could be the distal His bundle or the bundle branches.

Evaluation and management of patients after surgical repair of congenital heart diseases

A N ESTIMATED 25,000 babies are born each year with congenital heart disease in the United States.’ Until the last decade, the great majority of patients who reached adulthood had either mild abnormalities or had undergone successful surgery for a single, usually simple defect. These individuals were virtually all hemodynamically normal, and rarely developed late complications which would require further management. In the past 10 yr however, technical advances and remarkable surgical accomplishments have led to physiologic correction of a large number of patients who hitherto would not have reached maturity. Thus, among the present generation of children who have been operated upon for congenital heart disease, many will emerge into adulthood with “repaired” complex lesions, and some will present to the adult cardiologist and internist with a number of new diagnostic and therapeutic challenges. The purpose of this review is to provide physicians with information regarding potential late complications and the management of the postoperative patient after cardiac surgery for congenital heart disease. Special problems associated with repair of specific defects will be outlined, and questions will be considered regarding the eventual clinical effects of mild residual anatomic, hemodynamic, and electrocardiographic abnormalities.