Purpose of the observational study is to assess the capability of a satellite tele-echocardiography (STE) system to acquire and transmit echocardiographic images and clips to an echocardiographic core laboratory (ECL) in a real time mode without loss of quality. Additionally the prognostic efficacy of specific echo parameters in the cardiac resynchronization therapy response will be evaluated.

CORELAB-CRT is a prospective multi center Italian observational study. All echo images and clips will be transmitted by using an integrated satellite transmission system. All echo assessments performed in accordance to the centers clinical practice will be also used to investigate the prognostic efficacy of echo parameters in term of response to the cardiac resynchronization therapy (CRT). All commercially available multi-chamber CRT-D devices from any manufacturers are allowed in this observational study.

Any compatible market released right atrial, right ventricular and left ventricular lead from any manufacturer is allowed.

The echocardiography device models used to perform echo imaging for all patients participating in this analysis are GE Vivid 7, GE Vivid 9 and GE Vivid I, according to the model used in the clinical practice of the hospital.

Inclusion Criteria:

1. NYHA class II, III and ambulatory IV with:

   • QRS complex duration ≥120msec;
   • Ejection fraction ≤35%.

2. Optimized medical treatment;

3. Patient in sinus rhythm;

4. Patient is willing and able to sign an informed consent form.

Exclusion Criteria:

1. Unstable angina, or acute myocardial infarction, coronary-aortic bypass graft or percutaneous transluminal coronary angioplasty within the past 3 months;
2. Cerebral vascular attacks or transient ischemic attack within the last month;
3. Chronic atrial arrhythmias, paroxysmal atrial fibrillation events;
4. Patients already implanted with an ICD or a CRT device;
5. Pacemaker dependency or ventricular pacing percentage ≥10%;
6. Valvular disease with an indication for surgical correction ≤12 months survival expectancy;
7. Mechanical right ventricular valve;
8. Patient is enrolled in or intends to participate in another clinical trial that may have an impact on the study endpoints;
9. Pregnancy or breastfeeding;
10. Previous heart transplant;
11. Refusal of study informed consent;
12. Expected lack of compliance during follow-up;
13. Patient is less than 18 years of age;
14. Patient's life expectancy is less than 6 months in the opinion of physician.

In accordance with the current ESC/ACCF/AHA indications for CRT in sinus rhythm, all patients in NYHA class II, III and IV with QRS complex greater than 120 msec and ejection fraction equal or less than 35% will be considered eligible to participate in this observational study.