<qa>  What is the name of the type of therapy that is required to treat a Cardia- Cardiac arrhythmia requiring anti-arrhythmic therapy. Subjects receiving digoxin, calcium channel blockers except verapamil, or beta-adrenergic blockers except propranolol are eligible at the investigator s discretion if the dose has been stable for at least 2 weeks before the start of study treatment. Subjects with sinus arrhythmia and infrequent premature ventricular contractions are eligible at the investigator s discretion. 