Cardiac resynchronisation therapy (CRT) is indicated in patients with heart failure (moderate to severe), systolic dysfunction (left ventricular ejection fraction <35%) and prolonged QRS duration despite being treated with appropriate pharmacotherapy. CRT works through simultaneous pacing of the right and left ventricles. The goal of CRT is to improve the patient's left ventricular dyssynchrony which is largely secondary to a left bundle branch block. CRT devices may also have defibrillator capacity ^1-2.