Biomedical subjects
Publications and source records attributed to T McDonough.
The wide range of normal sinus node function makes identification of dysfunction difficult. Emphasis is placed upon real time correlation of ECG bradyarrhythmia with typical symptoms. A spectrum of atrial electrical dysfunction is described which includes abnormalities of the sinus and AV nodes as well as failure of escape pacemakers and atrial tachyarrhythmias.
The safety and efficacy of the intravenous (IV) calcium channel blocker, verapamil, in controlling the ventricular response or converting to sinus rhythm patients with atrial flutter or atrial fibrillation were assessed. Seventeen patients (nine with atrial flutter and eight with atrial fibrillation) with these arrhythmias that were difficult to control pharmacologically were chosen for the study. All patients at the time of study were receiving digoxin. Either verapamil or placebo was chosen randomly and a bolus of 0.075 mg/kg (up to 5 mg) was administered. Twelve patients had a marked reduction in their ventricular response after IV administration of verapamil (seven with atrial flutter and five with atrial fibrillation). None of these 12 patients converted (nonconverters). The average reduction in heart rate was from 120 +/- 6 beats per minute to a minimum of 83 +/- 13 beats per minute within 20 minutes after drug administration. Verapamil was found to convert five patients with atrial arrhythmias to sinus rhythm (two with atrial flutter and three with atrial fibrillation) (converters). In addition, three patients with atrial arrhythmias of less than one month who did not convert with parenteral drug therapy converted within 24 hours while receiving the oral drug. Converters had their supraventricular arrhythmias of significantly shorter duration (median, three hours v 30 days) and tended to have smaller left atrial size (3.8 +/- 0.7 cm v 4.3 +/- 1.3 cm) compared with the nonconverters. We conclude that verapamil is safe and effective when administered IV to patients with atrial flutter and fibrillation for control of ventricular response. In short duration atrial arrhythmias, conversion to sinus rhythm is likely once the ventricular response is controlled.
Donor sinus node dysfunction is an uncommon event after orthotopic heart transplantation. In the past treatment of persistent symptomatic bradycardia in the setting of orthotopic heart transplantation has been accomplished by implantation of a single transvenous lead system with loss of atrioventricular synchrony and rate responsiveness or by implantation of a multiple transvenous lead system in which the multiple leads present a mechanical limitation to endomyocardial biopsy. To preserve atrioventricular synchrony, avoid the mechanical limitations of a ventricular lead at the time of routine biopsies, and maintain some degree of rate responsiveness during exercise, we elected to implant an activity-detecting pacing system with a single bipolar transvenous atrial lead in two of our orthotopic heart transplant recipients with persistent symptomatic donor sinus node dysfunction. This article details the techniques used and the results obtained in what we believe to be the first two implantations of this unique pacing system in orthotopic heart transplant recipients.