Corrected QT (QTc) interval >=480 msecs History of acute coronary syndromes (including myocardial infarction or unstable angina) within 6 months prior to first dose of study treatment Coronary angioplasty, or stenting within the past 24 weeks; A history or evidence of current Class II, III, or IV heart failure as defined by the New York Heart Association (NYHA) guidelines; Treatment refractory hypertension defined as a blood pressure of systolic >140 mmHg and/or diastolic >90 mmHg which cannot be controlled by antihypertensive therapy; Abnormal cardiac valve morphology ( >=Grade 2) documented by echocardiogram (subjects with Grade 1 abnormalities [i.e., mild regurgitation/stenosis] can be entered on study). Subjects with moderate valvular thickening should not be entered on study; Patients with intra-cardiac defibrillators A history or evidence of current clinically significant uncontrolled arrhythmias; Exception: Subjects with atrial fibrillation controlled for > 30 days prior to randomization are eligible.