Multicenter Automatic Defibrillator Implantation Trial - Chemotherapy-Induced Cardiomyopathy

Inclusion Criteria: * Age 18 (or of legal age to give informed consent specific to state and national law) up to 80 years of age * Male or Female * Without clinical heart failure at initiation of chemotherapy/radiation-induced treatment for an underlying malignancy, but developed clinical heart failure (cardiomyopathy: reduced left ventricular ejection fraction (LVEF) with a left bundle branch block (LBBB)-type of conduction disturbance; see next inclusion item) 6 months or more after initiation of the chemotherapy without other evident cause of the cardiomyopathy. * Eligible for implantation of a CRT-D (cardiac resynchronization therapy-defibrillator) device according to one of the following options in currently available guidelines: 1. Class 1: Left ventricular ejection fraction (LVEF) less than or equal to 35% AND sinus rhythm AND LBBB (left bundle branch block) with a QRS (electrocardiographic depolarization duration) duration greater than or equal to 150ms AND NYHA (New York Heart Association) class II, III or ambulatory IV symptoms on guideline-directed medical therapy 2. Class 2a1: Left ventricular ejection fraction (LVEF) less than or equal to 35% AND sinus rhythm AND left bundle branch block (LBBB) with a QRS (electrocardiographic depolarization duration) duration 120-149ms AND New York Heart Classification (NYHA) class II, III or ambulatory IV symptoms on guideline-directed medical therapy 3. Class 2a2: Left ventricular ejection fraction (LVEF) less than or equal to 35% AND sinus rhythm AND Non-left bundle branch block (LBBB) with a QRS(electrocardiographic depolarization duration) duration greater than or equal to 150ms AND New York Heart Classification (NYHA) class III or ambulatory IV symptoms on guideline-directed medical therapy * On stable optimal pharmacologic therapy for the cardiac condition that is guideline-based and may include one or more of the following medications: Loop diuretics, Angiotensin converting enzyme (ACE) inhibitors and/or angiotensin receptor blocker (ARB), Aldosterone antagonists and/or Beta-blockers unless the subject is not indicated, contraindicated, or is intolerant of medication. Exclusion Criteria: * Currently implanted pacemaker or implantable cardioverter defibrillator (ICD) device * Previous implant with a CRT (cardiac resynchronization therapy)/CRT-D (cardiac resynchronization therapy-defibrillator) device * Cardiac condition not presumed to be caused by chemotherapy * Documented symptoms or hemodynamically unstable ventricular tachyarrhythmia * On active chemotherapy (must be at least 6 calendar months after last chemotherapy) * Permanent or chronic Atrial Fibrillation (AF), or cardioversion for AF within the past 3 calendar months before consent date * Structural heart disease such as congenital heart disease, valvular heart disease, e.g., rheumatic valvular heart disease, amyloid heart disease, etc. * Coronary artery bypass graft surgery or percutaneous coronary intervention within the past 3 calendar months before consent date * Enzyme positive myocardial infarction within the past 3 calendar months prior to consent date * Unstable angina requiring hospitalization, with diagnostic work up and intervention within the past 3 months prior to consent date * Angiographic evidence of coronary disease who are candidates for coronary revascularization and are likely to undergo coronary artery bypass graft surgery or percutaneous coronary intervention in the foreseeable future * Class IV and expected to undergo transplant within study duration * Current or past history of drug addiction or abuse that caused cardiomyopathy * Pregnant or plans to become pregnant during the course of the trial. * Recent cerebral vascular accident or transient ischemia attack within the previous 3 months prior to consent date * Presence of any disease, other than the subject's cardiac or cancer disease, associated with a reduced likelihood of survival for the duration of the trial, e.g., uremia, liver failure, active malignant disease, etc. * Participating in any other clinical trial * Unwilling or unable to cooperate with the protocol * Lives at such a distance from the clinic that travel for follow-up visits would be unusually difficult * Does not anticipate being a resident of the area for the scheduled duration of the trial * Unwilling to sign the consent for participation * Physician does not allow participation