Use of 3-D Blood Pool Scintigraphy to Guide Left Ventricular Pacing Lead Placement in Patients Requiring Cardiac Resynchronization Therapy

Heart failure (HF) has a prevalence of five million individuals in the United States. Approximately 25-30% of patients with HF due to left ventricular (LV) systolic dysfunction have prolonged QRS. Prolonged QRS duration (\>120ms) on ECG in HF patients is associated with increased morbidity and mortality. Delayed electrical activation of the LV translates to temporal delay in ventricular contraction. This is referred to as mechanical dyssynchrony. Patients with advanced HF, low ejection fraction (EF) of less than 35% and QRS of more than 120ms are indicated for cardiac resynchronization therapy (CRT). While most patients undergoing CRT implantation show dramatic improvement in HF symptoms, 30-40% of the HF patients undergoing CRT placement do not show a clinical response. The site of placement of the LV lead has been shown to be an important determinant of the effects of CRT. Measurement of left ventricular ejection fraction (LVEF) is performed using non-invasive measures such as the MUGA. By using the available information on left ventricular systolic function the investigators plan on investigating the effects of MUGA-guided versus traditional LV lead placement for CRT.