A patient was recently referred to me with advanced heart failure. She had been hospitalised and found to have very weak heart function (LVEF 20%). In addition, her ECG showed left bundle branch block (delay in electricle conduction to the left ventricle). A heart scan confirmed that the timing of contraction between the left and right heart chambers was severely affected. She did not have significant blockages of the heart arteries.
Cardiac resynchronization therapy (CRT) is a treatment to help the weak heart function with the right rhythm and to restore the normal timing pattern of the heartbeat. Pacemaker leads (or wires) are fixed in the right atrium and ventricle. An additional special lead is passed via a coronary vein to a left ventricular site. The specialised pacemaker can then optimise the timing intervals helping to restore better heart function.
The pictures below show that after the CRT was implanted, the ECG signals were more narrowed (QRS 174 to 137ms) indicating more optimised contraction of the heart chambers.