CRT which is also referred to as biventricular pacing, is often recommended for patients with severe heart dysfunction and congestive heart failure.  Approximately 30% of patients with congestive heart failure have an abnormality of their electrical conduction system which causes the two ventricles in the heart to beat asynchronously and sequentially.  Normally, the ventricles should beat simultaneously. This worsens the function of an already damaged heart.

CRT resynchronizes the two ventricles by pacing both chambers simultaneously.  By coordinating the contraction of the heart, efficiency of the heart is improved and the work of the heart to pump blood is diminished.

Studies have shown that in properly selected patients more than half will have improvement in symptoms of shortness of breath, and will have improved exercise tolerance.  Ejection fraction, a measure of heart function obtained by an echocardiogram, can also significantly improve and in rare patients the heart function can dramatically improve to reach near normal from biventricular pacing.