Challon J. Murdock

Efficacy of flecainide for the reversion of acute onset atrial fibrillation

The efficacy and safety of intravenous flecainide to convert recent-onset atrial fibrillation (AF) (present for greater than or equal to 30 minutes and less than or equal to 72 hours and a ventricular response greater than or equal to 120 beats/min) was investigated. A total of 102 patients without severe heart or circulatory failure were randomized to receive either intravenous flecainide (2 mg/kg, maximum dose 150 mg; 51 patients) or placebo (51 patients) in a double-blind trial. Digoxin (500 micrograms intravenously) was administered to all patients who had not previously been receiving digoxin. The electrocardiogram was monitored continuously during the study. In 29 (57%) patients stable sinus rhythm was restored within 1 hour after flecainide and in only 7 (14%) given placebo (chi square 18.9; p = 0.000013; odds ratio 8.3; 95% confidence interval 2.9-24.8). Reversion to sinus rhythm within 1 hour after starting the trial medication was considered a pretrial end point and likely to be due to a drug effect. At the end of the 6-hour monitoring period, 34 patients (67%) in the flecainide group were in sinus rhythm whereas only 18 (35%) in the placebo group had reverted (chi square 8.83, p = 0.003; odds ratio 3.67; 95% confidence interval 1.5-9.1). Significant hypotension, although short lived, was more common in the flecainide group. One patient given flecainide developed torsades de pointes and was successfully electrically cardioverted. Flecainide is useful for the management of recent-onset AF both for control of the ventricular response and conversion to sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation Between the Ventricular Electrogram Amplitude in Sinus Rhythm and in Ventricular Fibrillation

During testing of implantable defibrillators, ability to sense ventricular fibrillation is assessed by observing electrograms and the emitted ECG interpretation channel during induced ventricular fibrillation. We hypothesized that ventricular electrogram amplitude in sinus rhythm could be used to predict the ventricular electrogram amplitude in ventricular fibrillation and serve as a first approximation of the “safety margin” for sensing ventricular fibrillation. We compared the peak‐to‐peak epicardial ventricular electrogram during sinus rhythm and ventricular fibrillation in 12 patients undergoing defibrillator impJantation. The ventricular electrogram was recorded with an integrated bipolar lead and Altered at 10–50 Hz. Ventricular fibrillation was induced by alternating current and the ventricular electrogram measured from cessation of alternating current to the first countershock. The mean ventricular electrogram amplitude in sinus rhythm was 15.3 ± 5.4 mV (range 7.1–25.5) and in 37 episodes of ventricular fibrillation was 8.3 ± 3.6 mV frange 2.1–16.3). There was a significant relationship between the mean ventricular electrogram amplitude in sinus rhythm and in ventricular fibrillation (R = 0.7, P < 0.001). There was wide variation among individuals in the decrease in the mean ventricular electrogram amplitude during ventricular fibrillation, with the ratio of mean ventricular electrogram in sinus rhythm to mean ventricular electrogram in ventricular fibrillation ranging from 0.29 to 1.05 (mean 0.55 ± 0.20). This suggests that up to a fourfold decrease may be expected in the mean ventricular electrogram amplitude during ventricular fibrillation. These results suggest that there is a relationship between the mean ventricular electrogram in sinus rhythm and in ventricular fibrillation which is useful as an initial approximation in assessing sensing lead function and programming device sensitivity levels.

Radiofrequency Catheter Ablation of Refractory Ventricular Tachycardia

Transcatheter radiofrequency ablation of the arrhythmia focus was attempted in a 68‐year‐old patient with recurrent ventricular tachycardia, both spontaneous and inducible by programmed ventricular stimulation despite treatment with multiple antiarrhythmic drugs. The procedure was performed under local anesthetic without complication. The arrhythmia was not inducible immediately following ablation or 5 days later, and during 5 months follow‐up there has been no spontaneous recurrence.

Significance of minimal preexcitation in Wolff-Parkinson-White syndrome.

Abstract The degree of preexcitation in the Wolff-ParkinsonWhite (WPW) syndrome depends on the relative degree of ventricular activation through the accessory pathway and the atrioventricular nodal system. A minimal preexcitation pattern may be related to rapid conduction over the normal atrioventricular conduction system, delayed intraatrial conduction to the atrial insertion of the accessory pathway, slower conduction over the accessory pathway, or a combination of these factors. We hypothesized that a minimal preexcitation pattern generally reflects a longer intraatrial conduction time and may be of value in localizing a pathway to the left lateral region. This study examined the incidence of minimal preexcitation pattern and its potential as an electrocardiographic pathway-localizing feature in patients with WPW syndrome.