Procainamide-induced sinus node dysfunction in patients with chronic renal failure

Pulmonary Vein Isolation for Atrial Fibrillation in Patients with Symptomatic Sinus Bradycardia or Pauses

INTRODUCTION

Sick sinus syndrome is commonly associated with tachyarrhythmias and bradyarrhythmias that often are symptomatic. The aim of this study was to assess the effect of pulmonary vein isolation in patients with sick sinus syndrome and atrial fibrillation (AF).

METHODS AND RESULTS

Three hundred fourteen consecutive patients who underwent pulmonary vein isolation between December 2000 and January 2002 were included in the study. Thirty-one patients had sick sinus syndrome, which was defined as a preprocedural history of symptomatic sinus bradycardia or pauses. Endpoints included AF recurrence, change in the frequency of sinus pauses, and symptoms of presyncope or syncope, as well as mean heart rate and percentage of atrial pacing in patients with pacemakers implanted prior to the pulmonary vein isolation. Patients had AF for an average of 6 +/- 3 years. Patients were 58 +/-8 years old and had ejection fractions of 55 +/- 4%. Sixty-one percent had implanted pacemakers. AF recurred within 6 months in 4 patients. Two had a successful second pulmonary vein isolation procedure. There were no recurrences of presyncopal events (P < 0.05) or documented sinus pauses (P < 0.05) after successful pulmonary vein isolation in the patients without permanent pacemakers. Patients with pacemakers had a 13-fold reduction in the percentage of atrial pacing (P < 0.05). Both groups showed a significant increase in average heart rates at 6-month follow-up.

CONCLUSION

Cure of AF by pulmonary vein isolation helped resolve the clinical manifestations of sick sinus syndrome, suggesting that the occurrence of AF and/or the associated treatment could be partially responsible for sick sinus syndrome.

Differing electrophysiological effects of class IA, IB and IC antiarrhythmic drugs on guinea-pig sinoatrial node

Standard microelectrode techniques were used to study the effects of class IA (quinidine, disopyramide, procainamide), IB (lignocaine, mexiletine, tocainide) and IC (flecainide, encainide, lorcainide) antiarrhythmic drugs on action potentials in spontaneously beating sino-atrial node cells from guinea-pigs. The IA drugs all produced significant slowing of spontaneous rate in therapeutic concentrations. The IB agents did so only in concentrations well above therapeutic levels and the IC drugs were of intermediate potency. All nine drugs markedly slowed the repolarization rate and this was the major mechanism of sinus slowing for the IA and IC compounds. The IB drugs shared this effect but prolongation of phase 4 by reduction of the slope of diastolic depolarization was also a prominent feature of their action.

Sinus node function and dysfunction

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.