Patients with reduced left ventricular function are at an increased perioperative risk and often need prolonged postoperative treatment on intensive care units. A significant portion of these patients require postoperative pacing. Right ventricular pacing has been shown to be hemodynamically deleterious The aim of this study is to determine which biventricular pacing after cardiac surgery, in patients with reduced left ventricular function (EF≤ 45%), is hemodynamically favourable.

Some patients with left ventricular systolic dysfunction (LVSD) have an inefficient pumping function. These patients have been shown to benefit from a device therapy known as biventricular pacing. Biventricular pacing causes a more coordinated contraction of the heart chambers resulting in improvement in the pumping ability of the heart and blood pressure. Cardiac Resynchronization Therapy (CRT) has established itself as a proven therapy for congestive heart failure in adults, patients showing improvement in exercise tolerance, quality of life, and survival.

In cardiac surgery, a significant number of these patients with left ventricular systolic dysfunction require postoperative pacing. Right ventricular pacing has been shown to be hemodynamically deleterious Whether biventricular pacing in patients with LVSD improves patient outcomes after heart surgery has not been investigated.

The aim of this crossover trial is to compare conventional ventricular pacing and DDD-biventricular in post operative patients with a pre operative ejection fraction less than 45%, in a prospective randomized setting.

We would like to determine whether biventricular pacing optimized by trans thoracic echocardiography of left ventricular, immediately after heart surgery in patients with LVSD will improve the heart function.

Immediately after surgery, the patients will receive atrio ventricular conventional right ventricular pacing, or biventricular pacing depending upon the treatment arm that they were randomized to.

The primary end point is a 15 % improvement in index cardiac measured by thermal dilution and/or echocardiography in intensive care unit.

Furthermore, Plasma N-terminal pro-brain natriuretic peptide (NT-proBNP), cardiac troponin T (cTnT), will be measured in patients undergoing elective cardiac surgery 12 h, 24 h, 48 h and 72 hours after.

This study is important because of a high probability of clinical benefit.

Inclusion Criteria:

• Planned CABG and/or valve surgery
• Left ventricular dysfunction (EF≤ 45%)
• Age > 18 years
• able to give written information consent

Exclusion Criteria:

• Existing permanent pace maker
• Atrial fibrillation
• Enrolment in other research protocols
• Inability to give written informed consent
• Heart transplant
• Pre operative cardiovascular instability