Heart failure is the most rapidly growing cardiovascular condition in developed countries. Despite advances in medical therapy, patients with heart failure are at high risk for death and hospitalization. Cardiac Resynchronization Therapy - defibrillators (CRT-D) are an effective treatment for heart failure.

Despite the high success rate of a CRT-D implant, there is a possibility of 10% that the LV lead cannot be implanted in patients undergoing a trans-venous system implantation. In this case, the patients may undergo multiple procedures before a lead is successfully implanted. These implant failures are not due to patient selection but rather to patients heart anatomy leading to lead stability problems, phrenic nerve stimulation (also called diaphragmatic stimulation) and poor electrical measurements.

The phrenic nerve is not part of the heart but runs near to this area on the way to a large muscle, called diaphragm, which separates the lung space from the space containing stomach, liver, kidneys and other internal organs in the abdomen. If the lead electrode is close to this nerve, it can cause a small part of it to contract giving you an uncomfortable hiccupping sensation.

In many patients, phrenic nerve stimulation is not identified until after the implant procedure when movement and postural changes bring the LV lead into closer contact with the phrenic nerve.

The investigation is performed to demonstrate the equality of performance of two different modalities of optimization of the implanted device and Quartet lead, Empirical (anatomical) optimization and Right Ventricle Left Ventricle (RVLV) conduction delay optimization.

Inclusion Criteria:

• Male or female patients ≥ 18 years of age
• Patient met standard CRT-D device indications (Left Ventricular Ejection Fraction (LVEF) ≤ 35%, QRS ≥ 120 ms, New York Heart Association (NYHA) Class II, III or ambulatory Class IV Heart Failure (HF) symptoms with optimal recommended medical therapy) and will be implanted with an St Jude Medical CRT-D
• Patient is willing to provide written informed consent.

Exclusion Criteria:

• Patient with non left bundle branch block (RBBB, intraventricular delay (IVCD) Block)
• Patient has an epicardial ventricular lead system.
• Patient has limited intrinsic atrial activity (≤ 40 bpm).
• Patient has persistent or permanent Atrial Fibrillation.
• Patient's life expectancy is less than 1 year
• Patient is pregnant.
• Patient is dependent on IV inotropic agents.