Patients with all degrees of renal dysfunction are allowed including patients on hemodialysis; patients with mild to severe hepatic dysfunction are allowed as defined below: Patients with both hepatic and renal dysfunction will also be excluded Patients with abnormal liver function will be eligible and will be grouped according to the criteria described; patients with active hemolysis should be excluded; no distinction will be made between liver dysfunction due to metastases and liver dysfunction due to other causes History of complex ventricular or supraventricular arrhythmias Significant ventricular arrhythmias (> 20 premature ventricular contractions [PVCs]/min due to gating difficulty) atrial fibrillation with uncontrolled ventricular response Current or history of hepatic dysfunction No distinction should be made between liver dysfunction due to metastases and liver dysfunction due to other causes Complete left bundle branch block Right bundle branch block + left anterior hemiblock (bi-fascicular block) Patients with right bundle branch block plus left anterior hemiblock, bifascicular block are excluded Radiographic evidence of hydrocephalus or other architectural distortion of the ventricular system, including placement of external ventricular drain or ventriculoperitoneal shunt Any clinically important abnormalities in rhythm, conduction or morphology of resting electrocardiography (ECG) (e.g., complete left bundle branch block, third degree heart block, second degree heart block) Radiographic evidence of hydrocephalus or other architectural distortion of the ventricular system, including placement of external ventricular drain or ventriculoperitoneal shunt Patients receiving medications for treatment of left ventricular systolic dysfunction