Ivabradine Versus Beta-Blockers in Patients with Conduction Abnormalities or Left Ventricular Dysfunction Undergoing Coronary Artery Bypass Grafting

Postoperative rhythm disorders are a serious complication of coronary surgery and they are associated with increased morbidity and mortality. Atrial fibrillation is the most common complication after cardiac surgery, with an incidence of 30% after coronary artery bypass grafting (Camm et al.,2010). There are few data about the etiology of atrial fibrillation in this setting, factors such as intraoperative atrial ischemia, pericarditis, and excessive adrenergic stimulation, were incriminated in its occurrence in vulnerable patients (Lucio et al., 2004). The peak incidence of postoperative atrial fibrillation is between postoperative days 2 and 4 (Camm et al.,2010). Although frequently these arrhythmias are benign and transient, patients developing postoperative atrial fibrillation are more likely to have perioperative myocardial infarction, stroke, congestive heart failure, respiratory failure, prolonged hospitalization and intensive coronary unit (ICU) stay and therefore increased economic burden of their care (Lucio et al., 2004; Iliuta et al., 2009; Burgess et al., 2006). Many clinical trials and multiple meta-analyses evaluated the efficacy of pharmacological and non-pharmacological interventions in prevention of postoperative atrial fibrillation. The metaanalyses and systematic reviews showed that interventions to prevent and/or treat postoperative atrial fibrillation with beta-blockers, sotalol, or amiodarone and, less convincingly, atrial pacing, are favoured with respect to outcome (atrial fibrillation occurence, stroke, and length of hospitalisation) (Burgess et al., 2006; Crzstal et al., 2004). Currently, preoperative or early postoperative administration of beta-blockers is considered a first line choice to prevent atrial fibrillation after coronary artery bypass grafting except in patients with contraindications to beta-blocker therapy (Camm et al.,2010; Eagle et al., 2004). In patients with conduction abnormalities, severe left ventricular dysfunction, active bronchospasm or marked resting bradycardia the use of beta-blockers is difficult and controversial. The hyperpolarization-activated pacemaker current (If) channel inhibitor ivabradine, which induces heart rate reduction by selective sinus node inhibition, showed improvement of clinical outcomes in patients with stable coronary artery disease and left ventricular systolic dysfunction (Fox et al., 2008) or chronic heart failure (Swedberg et al., 2010). Data regarding