Contemporary management of atrial fibrillation

Comment on the article by Vázquez and Márquez-Garcia. High-risk vs. low-risk for thrombo-embolic events: Who are in the intermediate-risk group? What should be done then?

Although high risk and low risk profile for thrombo-embolic events have been extensively and intensively investigated in multi-centre trials and described in detail in atrial fibrillation guidelines, the management of those at otherwise intermediate risk is still a 'no-one's zone'. Individual risk profile is mandatory to identify those who will benefit of anti-coagulation therapy and large-scale clinical trials are still awaited to define efficacy and efficiency profile in intermediate-risk group.

Comparison of intravenous flecainide, propafenone, and amiodarone for conversion of acute atrial fibrillation to sinus rhythm

In a prospective, single-blind trial, we randomized 150 consecutive symptomatic patients with acute (< or = 48 hours' duration) atrial fibrillation to receive intravenous flecainide, propafenone, or amiodarone. Flecainide and propafenone were administered as a bolus dose of 2 mg/kg in 20 minutes. A second bolus dose of 1 mg/kg in 20 minutes was administered if conversion to sinus rhythm was not achieved after 8 hours. Amiodarone was administered as a bolus of 5 mg/kg in 20 minutes followed by a continuous infusion of 50 mg/hour. By the end of a 12-hour observation period, conversion to sinus rhythm was achieved in 45 patients (90%) in the flecainide group, 36 (72%) in the propafenone group, and 32 (64%) in the amiodarone group (p = 0.008 for the overall comparison, p = 0.002 for flecainide vs amiodarone, p = 0.022 for flecainide vs propafenone, and p = 0.39 for propafenone vs amiodarone). When compared with amiodarone, this higher reversion rate with flecainide was present from the first hour of the study period. However, only after administering the second bolus was there a significant difference between flecainide and propafenone. Median time to conversion to sinus rhythm was different among groups (p < 0.001), and it was lower in the flecainide (25 minutes; range 4 to 660) and propafenone (30 minutes; range 10 to 660) groups than in the amiodarone group (333 minutes; range 15 to 710; p < 0.001 for both comparisons). Flecainide, at the doses administered in this study, is more effective than propafenone and amiodarone for conversion of acute atrial fibrillation to sinus rhythm. Propafenone and amiodarone have similar conversion rates, although propafenone was faster in achieving the conversion to sinus rhythm.

Heart failure in patients with preserved left ventricular systolic function: do digitalis glycosides have a role?

It is being increasingly appreciated that a substantial number of patients with congestive heart failure (CHF) have relatively preserved systolic function. Although these individuals appear to have a somewhat better prognosis than those with low ejection fractions, they experience significant symptoms and frequently require hospitalization. In these patients, CHF is often attributed to left ventricular diastolic dysfunction, but this represents a potentially misleading over-simplification. In contrast to CHF associated with left ventricular systolic dysfunction, little is known about how to treat patients with preserved systolic function. Perhaps the major point of consensus has been that the use of digitalis glycosides is inappropriate in this group. Unexpectedly, however, in the recently completed Digitalis Investigators Group trial, a subgroup of nearly 1,000 patients with radionuclide ejection fractions > or = 45% experienced a similar reduction in heart failure endpoints with digoxin therapy as patients with 25% to 44% ejection fractions. The purpose of this article is to review the diverse causes of CHF with preserved systolic function and to examine the potential mechanisms by which digoxin may be producing beneficial effect in this setting.

Comparison of right atrial and peripheral procainamide infusion levels in patients with spontaneous or induced atrial fibrillation

As part of a new effort to develop an implantable drug infusion/pacing system to treat atrial fibrillation, this study examined the effects of rapid intracardiac procainamide infusion in humans with pacing-induced atrial fibrillation. Twenty patients with atrial fibrillation for > 5 minutes during an EP study received 500 mg of procainamide either via a peripheral venous infusion (n = 5) or directly in the right atrium (n = 15). Peak coronary sinus and femoral vein procainamide blood levels (mean +/- SEM) during 10, 5, and 3.3 minute central infusions were 17.0 +/- 4.1, 25.1 +/- 4.5, 45.6 +/- 5.1 and 11.3 +/- 3.2, 17.1 +/- 6.4, 18.7 +/- 5.0, respectively. In contrast, peak coronary sinus and femoral procainamide levels following the 5 minute intravenous infusion were 17.7 +/- 5.1 and 9.3 +/- 2.1. Changes in QT, QTc, QRS, and RI intervals were similar at each infusion rate. Systolic blood pressures (BP) decreased more with higher procainamide infusion rates but similar when comparing intravenous versus central drug administration at the same rate. The mean +/- SEM decreases in blood pressure with the 10, 5, and 3.3 min procainamide infusions were 12f5, 20f11, and 39f14, respectively. Conversion to sinus rhythm was not a primary endpoint given the often transient nature of acute atrial fibrillation in this setting. We conclude that significantly higher femoral vein and coronary sinus procainamide levels can be achieved by central rather than peripheral drug infusion. These data support that concept that rapid central infusion of anti-arrhythmic therapy can result in high intracardiac levels of antifibrillatory agents for the treatment of paroxysmal atrial fibrillation.

Prevention of thromboembolism in patients with atrial fibrillation

New insights into atrial physiology based on observations using transesophageal echocardiography are presented. The approach to anticoagulation of patients with both acute and chronic atrial fibrillation is reviewed within the context of the results of the major multicenter trials. These have provided some useful risk stratification guidelines for therapy. Presently available data suggest that the role of transesophageal echocardiography as a precardioversion screen is promising but requires further definition through clinical trials.