Treatment of ventricular arrhythmias after CAST

Long-term outcomes in patients treated with flecainide for atrial fibrillation with stable coronary artery disease

BACKGROUND

Class 1C antiarrhythmic drugs (AAD) have been associated with harm in patients treated for ventricular arrhythmias with a prior myocardial infarction. Consensus guidelines have advocated that these drugs not be used in patients with stable coronary artery disease (CAD). However, long-term data are lacking to know if unique risks exist when these drugs are used for atrial fibrillation (AF) in patients with CAD without a prior myocardial infarction.

METHODS

In 24,315 patients treated with the initiation of AADs, two populations were evaluated: (1) propensity-matched AF patients with CAD were created based upon AAD class (flecainide, n = 1,114, vs class-3 AAD, n = 1,114) and (2) AF patients who had undergone a percutaneous coronary intervention or coronary artery bypass graft (flecainide, n = 150, and class-3 AAD, n = 1,453). Outcomes at 3 years for mortality, heart failure (HF) hospitalization, ventricular tachycardia (VT), and MACE were compared between the groups.

RESULTS

At 3 years, mortality (9.1% vs 19.3%, P < .0001), HF hospitalization (12.5% vs 18.3%, P < .0001), MACE (22.9% vs 36.6%, P < .0001), and VT (5.8% vs 8.5%, P = .02) rates were significantly lower in the flecainide group for population 1. In population 2, adverse event rates were also lower, although not significantly, in the flecainide compared to the class-3 AAD group for mortality (20.9% vs 25.8%, P = .26), HF hospitalization (24.5% vs 26.1%, P = .73), VT (10.9% vs 14.7%, P = .28) and MACE (44.5% vs 49.5%, P = .32).

CONCLUSIONS

Flecainide in select patients with stable CAD for AF has a favorable safety profile compared to class-3 AADs. These data suggest the need for prospective trials of flecainide in AF patients with CAD to determine if the current guideline-recommended exclusion is warranted.

Is this finding relevant? Generalisation and epidemiology

The decision about whether the findings from analytical epidemiological studies can be extrapolated to another setting is an important one. We discuss some of the issues involved in the process of generalisation. A critical systematic qualitative approach should be used. This involves an assessment of the internal validity of the study and of the nature of the study base. The study subject matter and choice of epidemiologic measure should be considered. A study base similar to the target population is essential if the study is descriptive or if there is concern about effect modifiers whose effects cannot be predicted. In addition, data from quantitative tests of study findings in different populations should be considered.

Structural heart disease: its importance in association with antiarrhythmic drug therapy

The presence or absence of structural heart disease is an important factor to consider prior to initiating antiarrhythmic drug therapy with a class I or class III antiarrhythmic agent. An appropriate screen for structural heart disease and other associated proarrhythmic risk factors should include a complete history, physical examination, electrocardiogram (ECG), and echocardiogram in all patients; exercise test and Holter monitoring in many/most selected patients; and a signal-averaged ECG, chest x-ray, and invasive procedures only in selected/occasional patients. Whether and when to obtain the tests that are not indicated for all patients must be determined by each individual physician's practice strategy and philosophy, while keeping in mind the likelihood of finding an abnormality in a particular patient, the arrhythmia being treated, the nature of the drug to be used, and cost-effectiveness issues. Given the low incidence of proarrhythmia under most circumstances, screening for clinically unrecognized structural heart disease may appear difficult to justify in the current era of cost containment. However, due to the potential lethality of proarrhythmia, particularly in patients with structural heart disease, pre-drug assessment is prudent.