Stanley D. Beder

Ventricular arrhythmias in postoperative tetralogy of Fallot.

Ventricular arrhythmias in patients after total surgical repair of tetralogy of Fallot have been associated with late sudden death. In this large multicenter retrospective study of 359 patients with postoperative tetralogy of Fallot, spontaneous ventricular premature complexes (VPCs) on 24-hour ambulatory electrocardiographic monitoring and laboratory-induced ventricular tachycardia (VT) by electrophysiologic stimulation were analyzed. The mean age at surgical repair was 5 years and the mean follow-up duration after repair was 7 years. Spontaneous VPCs on ambulatory monitoring were found in 48% and induced VT on electrophysiologic stimulation was found in 17% of patients. Both spontaneous VPCs and induced VT were significantly related to delayed age at repair, longer follow-up interval, symptoms of syncope or presyncope and right ventricular systolic hypertension (greater than 60 mm Hg) (p less than 0.05), but not to right ventricular diastolic pressure greater than 8 mm Hg. The VPCs on ambulatory monitoring were more complex with increasing age at repair and follow-up duration. Induction of VT on electrophysiologic stimulation correlated with spontaneous VPCs including VT on 24-hour ambulatory electrocardiographic monitoring. The electrophysiologic stimulation protocol varied and the induction of VT increased with a more aggressive stimulation protocol. While induced sustained monomorphic VT was related to all forms of spontaneous VPCs, induced nonsustained polymorphic VT was related to more complex forms of VPCs on ambulatory monitoring. VT was not induced in asymptomatic patients who had normal 24-hour ambulatory electrocardiographic monitoring and normal right ventricular systolic pressure. (ABSTRACT TRUNCATED AT 250 WORDS)

Symptomatic sick sinus syndrome in children and adolescents as the only manifestation of cardiac abnormality or associated with unoperated congenital heart disease

Sick sinus syndrome (SSS) occurs infrequently in children who have not undergone cardiac surgery. The symptoms, electrocardiograms, and electrophysiologic data in 11 patients aged 2 to 17 years who had nonsurgical SSS were reviewed. Syncope occurred in 5 patients and sinus bradycardia in 9. Sinus nodal recovery times were prolonged in 6 patients. The atrial effective refractory period was prolonged in 2 patients and the atrioventricular nodal functional or the effective refractory period, or both, was prolonged in 5 patients. Because patients with nonsurgical SSS may have abnormalities not only of the sinus node but also of the atrium and the atrioventricular node, it is recommended that patients with symptomatic SSS be evaluated by electrophysiologic study. The proper choice of antiarrhythmic drug therapy or permanent pacing procedure depends on a complete analysis of the cardiac conduction system.

Effect of ouabain on the anterograde effective refractory period of accessory atrioventricular connections in children

The anterograde effective refractory period of the accessory connection was determined before and after the administration of ouabain (0.015 mg/kg intravenously) during electrophysiologic studies in 21 patients with Wolff-Parkinson-White syndrome. The mean age (+/- standard deviation) was 10 +/- 2 years (range 1 month to 31 years). Each patient had stopped taking all cardiac drugs for more than 36 hours. Determination of the anterograde effective refractory period of the accessory connection was made using the atrial extrastimulus technique. A change in the anterograde refractory period of the accessory connection was defined as an increase or decrease of greater than 10 ms from the value before ouabain administration. The post-ouabain anterograde effective refractory period of the accessory connection increased in 2 (9%) of the 21 patients, decreased in 9 (43%) and was unchanged in 10 (48%). This study demonstrated a decrease in the anterograde effective refractory period of the accessory connection of 43% of patients with Wolff-Parkinson-White syndrome after the administration of ouabain.

Laser Atrial Septostomy: An Engineering Problem

The purpose of this study was to develop a reproducible method for atrial septostomy in live animals, which would be independent of both atrial septal thickness and left atrial size. Seven mongrel dogs monitored electrocardiographically were anesthetized and instrumented with systemic and pulmonary arterial lines. A modified Mullins transseptal sheath was advanced under fluoroscopic control to interrogate the left atrium and atrial septum. A 400 micron regular quartz or a laser heated metallic tip fiber was passed through the sheath up to the atrial septum. Lasing of the atrial septum was done with an Argon laser at power output of 5 watts. In three dogs, an atrial septosomy catheter was passed to the left atrium through the laser atrial septostomy and balloon atrial septostomy was performed. The laser atrial septostomy measured 3 x 5 mm in diameter. This interatrial communication could be enlarged with a balloon septostomy to over one cm in diameter. Hemodynamic and electrocardiographic monitoring were stable during the procedure. Engineering problems included: 1) radioluscency of the laser fibers thus preventing fluoroscopic localization of the fiber course; and 2) the inability to increase lateral vaporization of the atrial septum. It is concluded that further changes in the lasing fibers need to be made before the method can be considered for clinical use.

CONDUCTION ABNORMALITIES FOLLOWING REPAIR OF TETRALOGY OF FALLOT

Ventricular dysrhythmias following intracardiac repair of tetralogy of Fallot have been previously demonstrated. Less attention has been directed to postoperative conduction abnormalities in these patients. Between October, 1982 and March, 1984 we performed hemodynamic and electrophysiologic studies in 11 patients (8 males/3 females) who had previously undergone repair of tetralogy of Fallot. A wide spectrum of conduction system abnormalities including sinus node dysfunction (5/11), atrioventricular node dysfunction (3/11), and His-Purkinje disease (7/11) were found. Confirmation that bifasicular disease cannot be reliably diagnosed from the surface electrocardiogram alone was obtained. Spontaneous and/or inducible ventricular dysrhythmias were documented in 5/11 patients. However, there was no consistent relationship between the presence or degree of residual right ventricular hypertension and the presence of ventricular dysrhythmias. We conclude that: 1) frequent conduction abnormalities as well as ventricular dysrhythmias may occur in patients following repair of tetralogy of Fallot; and 2) ventricular dysrhythmias may occur in these patients even when residual right ventricular hypertension is not present. We therefore recommend that all patients should undergo postoperative hemodynamic and electrophysiologic study following intracardiac repair of tetralogy of Fallot.

PERMANENT PACING INDICATIONS FOLLOWING MUSTARD OPERATION FOR TRANSPOSITION OF THE GREAT ARTERIES

Sick sinus syndrome is a frequent complication following Mustard operation. Between October 1971 and May 1985, we performed the Mustard operation on 78 patients with transposition of the great arteries. Sixty-six patients were followed long-term for up to 10 years after surgery. We reviewed patient records and Holter monitor recordings in these latter 66 patients to determine if the degree of bradycardia predicted symptoms requiring permanent pacing. A total of 8/66 patients received pacemakers. Indications for pacing included asymptomatic bradycardia during the first postoperative month, symptomatic bradycardia (seizures and syncope) late following surgery, and use of antiarrhythmic drugs other than digoxin for the control of symptomatic atrial flutter or supraventricular tachycardia. The mean minimal heart rates documented by Holter monitor recordings did not differ significantly between the asymptomatic and symptomatic patients (p 0.15). We conclude that the degree of bradycardia is not a reliable predictor of symptoms or the need for pacing in postoperative Mustard patients during early and intermediate duration follow-up.

CHARACTERISTICS OF RIGHT VENTRICULAR ACTIVATION DETECTED BY BODY SURFACE POTENTIAL MAPPING AMONG POSTOPERATIVE TETRALOGY OF FALLOT PATIENTS WITH AND WITHOUT ARRHYTHMIA

In order to study myocardial activation, 15 patients with repaired Tetralogy of Fallot had body surface potential maps (BSPM) (180 electrode array). All had ambulatory EKG (H), exercise EKG (Ex) and intracardiac electrophysiology (EP). Advanced right bundle branch block (RBBB) was present in 12/15; partial RBBB in 1/15; no RBBB in 2/15. BSPM characteristics of advanced RBBB were lack of right ventricular (RV) breakthrough (12/12); low left ventricular peak to peak voltage (PPV)(1202 ± 544 UV); high RV PPV (3194 ± 1064);high T wave PPV (1549 ± 626) (consistent with “propagation” of repolarization); all significantly different from a normal population previously studied. Although advanced RBBB was “central” in 8/12 and “peripheral” in 4/12 by EP, no difference in RV activation was detected by BSPM among these two groups. Multiple RV activation centers (MC) were seen in 5/12; 5/5 having either sustained ventricular tachycardia (VT) during EP (3/5) or frequent premature ventricular contractions (PVC) on H or Ex (4/5). Without MC 1/7 had VT; 1/7 had PVCs (p< .01). Patients with MC had fractionation of intracardiac RV electrogram in 4/4 having EP mapping near the His bundle, (1/7 without MC) (p < .01). An anterior superior activation front was recognized in 8/12 with advanced RBBB, appearing 0-18 ms after initial RV activation, consistent with cell-cell propagation across the superior ventricular septum. We conclude: Within the spectrum of advanced RBBB, BSPM may show abnormalities of impulse propagation in the RV associated with ventricular arrhythmia.

PROGNOSIS OF NEWBORNS AND INFANTS WITH PREMATURE VENTRICULAR CONTRACTIONS

Between Sept 1982 and Oct 1984, we diagnosed premature ventricular contractions(PVCs) in 9 newborns and infants (3M/6F). CXRs were obtained in 6 patients(pts) and echocardiograms were performed in 8 pts. 7 pts were judged to have an otherwise normal heart while 1 pt was found to have a small VSD and another had mild peripheral PS. 24-hour Holter monitor recordings in 7 pts revealed frequent or infrequent uniform PVCs, infrequent multiform PVCs, uniform ventricular couplets, accelerated ventricular rhythm, and non-sustained uniform ventricular tachycardia. Frequent uniform PVCs were present in 6 pts and were completely suppressed during sinus tachycardia in 5/6. 1 pt was treated with propanolol (PR) which decreased but did not completely eliminate the PVCs. None of the other pts has received any antiarrhythmic treatment. Follow-up in these pts has ranged from 1 to 25 mos with a mean follow-up of 10.2 mos. At each pts most recent follow-up examination, PVCs were still present. All pts are alive and well and none have ever had any symptoms either at the time of initial diagnosis or during subsequent follow-up. We conclude that: 1)PVCs in newborns and infants with otherwise normal hearts are benign; & 2) antiarrhythmic treatment is unnecessary and does not influence an already excellent prognosis. We therefore recommend that newborns and infants discovered to have PVCs and no (or trivial)underlying heart disease be followed but not treated with antiarrhythmic drugs.