Cardiac resynchronization therapy (CRT) is a proven therapy in patients with severe left ventricular (LV) dysfunction with ejection fraction (EF)<35%., moderate to severe congestive heart failure and wide QRS in ECG. Positive response presents as improvement in quality of life, decrease in congestive hrat failure symptoms and signs, improvements in echocardiographic measurements and longer survival. About 30% of the patients do not respond to this treatment.

A decrease in clinical response to CRT is expected in patients with those predictors: advanced age, male, ischemic etiology of cardiomyopathy, Non-LBBB pattern in ECG, lack of mechanical dyssynchrony, large scar in LV, congestive heart failure stage IV, and non-cardiac co-morbidities (lung disease, pulmonary hypertension, renal failure and diabetes).

There are few solutions to increase the rate of clinical response to CRT, for example: endocardial pacing of LV or pacing a few simultaneous sites on LV. A study that investigated a method of simultaneous pacing on LV of patients with congestive heart failure and LBBB with QRS>150ms has shown major improvement of cardiac contraction (increased dP/dtmax) compared to a single pacing site over a postero-basal or lateral wall site).

Implantation of pacemaker leads- one in right ventricle (RV) and two over LV, i.e. multisite cardiac resynchronization therapy (MSCRT), has a few potential advantages, compared to conventional CRT.

Inclusion Criteria:

1. Patients with severe LV dysfunction, severe heart failure (NYHA FC III-IV and at least one hospitalization for congestive heart failure in the past 3 months before inclusion) on optimal medical treatment and that have narrow complex QRS or RBBB. These patients have an indication for ICD implantation.
2. Patients with conventional indications for CRTD implantation and EF<25%, QRS>150ms and severe heart failure (NYHA FC>III).
3. Patients with an indication for pacemaker implantation and an expected high rate of pacing (complete AV block or prior to AVN ablation) and a wish to avoid RV pacing (example: severe TR).
4. Patients with refractory ventricular tachycardia and severe LV dysfunction (EF<35%) that continue to have VT episodes despite antiarrhythmic drugs and despite recurrent VT ablations. Those patients have indication for ICD.
5. Patients with conventional indications for CRT but during implantation the anatomy is such that the site of implantation is not optimal (QRS>200ms). In these cases we will add an electrode in the opposite branch of the coronary sinus.

Exclusion Criteria:

Pregnancy

• Patients included in another study
• Patients that have other solutions that could avoid implantation (medications, ablation, etc