1. History of cardiac disease: congestive heart failure >NYHA class 2; active coronary artery disease (CAD) or myocardial infarction within the past 6 months (MI more than 6 months prior to study entry is allowed); cardiac arrhythmias requiring anti-arrhythmic therapy (beta blockers or digoxin are permitted) or uncontrolled arterial hypertension with systolic blood pressure >160 mmHg or diastolic blood pressure > 90 mm Hg despite optimal treatment