Advances in the treatment of atrial fibrillation: the future is now.

Abstract

Over the last decade, new therapies and the results of clinical trials have altered the landscape of the treatment of atrial fibrillation. These advances have improved our understanding of rate control, conversion modalities, maintenance of sinus rhythm and antiembolic measures. For rate control, once a day beta-blockers and calcium blockers have replaced digoxin as more effective rate control agents. The added benefit of betablockers prolonging survival in patients with depressed ejection fractions and data suggesting that calcium blockers may attenuate atrial electrical remodeling have contributed to their popularity. Intravenous amiodarone has been added to the armamentarium of more traditional intravenous rate control therapies. In refractory patients with rapidly conducting atrial fibrillation refractory to medical measures, AV junction ablation, with ablate and pace strategies, have demonstrated usefulness to improve symptoms and reverse tachycardia-induced-cardiomyopathy. The results of recent trials (PIAF, AFFIRM and RACE), comparing rate control and rhythm control strategies, have leveled the playing filed in making rate control an alternative option to treat atrial fibrillation patients instead of using more aggressive pharmacologic and nonpharmacologic therapies to maintain sinus rhythm. We now have a better understanding of acute therapies to convert atrial fibrillation to sinus rhythm. Intravenous ibutilide, oral dofetilide and oral bolus IC antiarrhythmics are now being used in appropriate patients in a cost-effective manner to convert atrial fibrillation to sinus rhythm. In patients unable to have their atrial fibrillation converted using monophasic shock wave direct current cardioversion, biphasic shock external Cardioversion has replaced internal direct current cardioversion as a method of choice. Data from the ACUTE trial has validated the role of transesophageal echocardiography as an alternative approach to safely convert patients while minimizing the risk of a thromboembolic event in patients who have persistent atrial fibrillation. Commercial approval of d, l-sotalol and dofetilide has added to our pharmacologic armamentarium to maintain sinus rhythm. Other new drug therapies, with novel mechanisms of action, are forthcoming. Drugs that are in clinical development include: azimilide (a once a day IKr and IKs blocker); dronedarone (an amiodarone-like drug without the iodine moiety); piboserod (a 5-HT4 receptor antagonist); RSD1235 (an atrial selective potassium inhibitor); ZP123 (facilitates conduction in the gap junction) and two intravenous drugs that are long acting A-1 adenosine antagonists. Data from multiple safety including EMIAT, CAMIAT, GESICA, CHF-STAT, DIAMOND and ALIVE have guided us to developing algorithms to safely choose antiarrhythmic drugs in patients with structural heart disease. The use of catheter ablation procedures to eradicate or isolate pulmonary vein triggers is changing the landscape as an alternative front-line treatment for the suppression of atrial fibrillation. Changes in procedure methodology have included pulmonary vein isolation instead of focal trigger ablation, the use of 3-dimensional mapping systems, intracardiac echocardiography and special mapping catheters. These advances have improved efficacy, decreased adverse effects, shortened procedure times and have helped improved our understanding of ablative therapies to treat patients with atrial fibrillation. In a large number of patients, ablation improves but does not eliminate atrial fibrillation. Such patients may need hybrid therapy, with the addition of antiarrhythmic drugs or atrial pacemakers/defibrillators to achieve an acceptable therapeutic endpoint. Recently, data from several trials have demonstrated that ACE inhibitors and angiotensin receptor blockers appear to be useful in preventing atrial fibrillation partially secondary to counteracting stretch activated channels and/or directly by blocking angiotensin-II. Recent studies suggest