Mark H. Cohen

Congenital heart block: development of late-onset cardiomyopathy, a previously underappreciated sequela.

OBJECTIVE We report 16 infants with complete congenital heart block (CHB) who developed late-onset dilated cardiomyopathy despite early institution of cardiac pacing. BACKGROUND Isolated CHB has an excellent prognosis following pacemaker implantation. Most early deaths result from delayed initiation of pacing therapy or hemodynamic abnormalities associated with congenital heart defects. METHODS A multi-institutional study was performed to identify common clinical features and possible risk factors associated with late-onset dilated cardiomyopathy in patients born with congenital CHB. RESULTS Congenital heart block was diagnosed in utero in 12 patients and at birth in four patients. Ten of 16 patients had serologic findings consistent with neonatal lupus syndrome (NLS). A pericardial effusion was evident on fetal ultrasound in six patients. In utero determination of left ventricular (LV) function was normal in all. Following birth, one infant exhibited a rash consistent with NLS and two had elevated hepatic transaminases and transient thrombocytopenia. In the early postnatal period, LV function was normal in 15 patients (shortening fraction [SF] = 34 +/- 7%) and was decreased in one (SF = 20%). A cardiac pacemaker was implanted during the first two weeks of life in 15 patients and at seven months in one patient. Left ventricular function significantly decreased during follow-up (14 days to 9.3 years, SF = 9% +/- 5%). Twelve of 16 patients developed congestive heart failure before age 24 months. Myocardial biopsy revealed hypertrophy in 11 patients, interstitial fibrosis in 11 patients, and myocyte degeneration in two patients. Clinical status during follow-up was guarded: four patients died from congestive heart failure; seven required cardiac transplantation; one was awaiting cardiac transplantation; and four exhibited recovery of SF (31 +/- 2%). CONCLUSIONS Despite early institution of cardiac pacing, some infants with CHB develop LV cardiomyopathy. Patients with CHB require close follow-up not only of their cardiac rate and rhythm, but also ventricular function.

Development of infundibular obstruction after percutaneous pulmonary balloon valvuloplasty

A 14 month old boy with suprasystemic right ventricular pressure secondary to pulmonary valvular stenosis and anular size of 10 mm underwent percutaneous balloon valvuloplasty with a 12 mm balloon. Right ventricular pressure almost doubled after valvuloplasty and the electrocardiogram revealed development of severe right ventricular strain. Both findings persisted on the following day. A postvalvuloplasty right ventriculogram demonstrated a severe systolic infundibular obstruction not present before. The patient underwent surgical relief of infundibular obstruction; successful opening of the pulmonary valve by the balloon valvuloplasty was observed. It is concluded that a balloon size 20% larger than anular size can be safe in human subjects and that infundibular obstruction may appear or even worsen after balloon valvuloplasty. Such an obstruction may be related to the severity of pulmonary valvular obstruction and a hypercontractile infundibulum.

Patency of the ductus arteriosus in normal neonates: Two-dimensional echocardiography versus doppler assessment

Two-dimensional echocardiography using a high resolution, 7.5 ,Jsz transduce was compared with Doppler echocardiography for the assessment of patency of the ductus arteriosus in normal newborn infants. Twenty-eight neonates were studied between 1 and 10 hours (mean 5.5) after birth and both examinations were possible in 27 (96%). Doppler echocardiography under two-dimensional direction indicated ductal patency in all 27 neonates. Doppler sampling in the pulmonary end of the ductus rather than the main pulmonary artery was more sensitive for detecting patency. When two-dimensional echocardiography only was used to predict patency, there was 85% sensitivity. Two-dimensional echocardiography showed no evidence of ductus arteriosus narrowing ion four neonates studied shortly after birth. In 18, the pulmonary portion of the ductus arteriosus appeared narrowed and in 8 of these, the narrowing extended toward the mid-portion of the ductus. In five others, there was only mid-ductus arteriosus narrowing. It is concluded that high resolution two-dimensional echocardiography can be used to assess ductus arteriosus morphology, but is limited in predicting ductal patency near the time of normal physiologic closure. Combined two-dimensional and Doppler echocardiography is a highly sensitive technique for detection of ductal patency when sampling is performed in the pulmonary end of the ductus arteriosus.

Two-dimensional echocardiographic assessment of pulmonary artery and aortic arch anatomy in cyanotic infants

To determine the feasibility and accuracy of noninvasive assessment of pulmonary artery and aortic arch anatomy, a prospective two-dimensional echocardiographic evaluation was performed in 20 consecutive cyanotic infants before cardiac catheterization and angiography. The echocardiographic assessment was correct with the following frequency: detection of left aortic arch in 13 of 13 infants, detection of right aortic arch in 7 of 7, identification of patent ductus arteriosus in 13 of 13 (one false positive finding), identification of a right pulmonary artery in 20 of 20, identification of a left pulmonary artery in 19 of 20, identification of the confluence of the right and left pulmonary arteries in 19 of 20 and identification of a main pulmonary artery in 14 of 16 (two false positive diagnoses by echocardiography). Echocardiographic estimates of arterial diameters were slightly smaller than those obtained by angiography. Mean vessel size (echocardiographic/angiographic diameter) was as follows: transverse aortic arch 8.6/10.6 mm, main pulmonary artery 5.7/6.3 mm, right pulmonary artery 4.1/4.2 mm and left pulmonary artery 4.2/3.9 mm. It is concluded that although two-dimensional echocardiography tends to underestimate vessel size, the qualitative assessment is adequate for planning a systemic to pulmonary artery anastomosis in selected infants with cyanotic forms of congenital heart disease.

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.

ALTERATIONS OF ENERGY METABOLISM IN HYPERTROPHIED HEARTS DURING ANOXIA: A P-31 NUCLEAR MAGNETIC RESONANCE STUDY

The metabolic effect of anoxia on hypertrophied myocardium was investigated using P-31 NMR spectroscopy. Hearts from 18 mo. SHR (hypertrophied, n=7) and age-matched WKY (control, n=6) rats were mounted on a modified Langendorff apparatus, paced at 240/min and perfused with 36°C phosphate-free, glucose-containing buffer bubbled with oxygen or nitrogen (anoxia). Left ventricular pressure (LVP), LV dP/dt and perfusion pressure were continuously recorded while consecutive 3-min spectra were collected. This allowed temporal assessment of myocardial phosphate levels [incl. inorganic phosphate (Pi), creatine phosphate (CP) and ATP] during baseline conditions, anoxia and recovery. Anoxia was maintained until a 70% fall in LVP occured. Compared to the WKY, SHR rats had higher in vivo BP (163 vs 104; p<.001) and cardiac hypertrophy (heart/ body weight = 5.3 vs 3.5 mg/g; p<.001). During baseline perfusion, SHR hearts had higher resistance (9.8 vs 5.9 mmHg/cc/min/g; p=.003) but no significant difference in LVP or dP/dt. SHR hearts demonstrated a faster fall in high-energy phosphates and LVP during anoxia (SHR fell to 30% baseline LVP in 8.5 vs 13.0 mins; p=.018). Throughout the protocol SHR hearts had lower CP (3.8 vs 5.6 umoles/g; p=.008), ATP (3.2 vs 3.9 umoles/g; p=.047) and CP/Pi ratio (1.5 vs 2.5; p=.043). We conclude that chronically hypertrophied hearts have: (1) less ATP/g and CP/g than age-matched controls, and (2) a faster decline in mechanical and metabolic function during anoxia.

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.