Cardiac Resynchronization Devices are built on the same principle as that of pacemakers. Pacemakers are basically used to relieve symptoms due to an excessively slow heartbeat. The device constantly monitors the heartbeat and whenever necessary it gives tiny imperceptible signals to stimulate the heartbeat.
It consists of two electrode wires or leads. One is implanted in the right atrium and the other in the right ventricle. This helps to coordinate the pumping action of the various chambers of the heart. The CRT device has three leads as opposed to the typical pacemaker which has two leads. An electrical pulse generator is kept under the skin of the upper chest. Two leads from this pulse generator are given to the right atrium and the right ventricle. In addition to this the third lead is positioned in a vein on the surface of the left ventricle.
These leads allow the CRT device to stimulate both the ventricles simultaneously thus obtaining a coordinated squeezing pattern. Since both the ventricles are stimulated at the same time it is also known as Bi ventricular Pacing. The main advantage of this is that it reduces the electrical delay and results in a more efficient pumping action.
Certain Studies conducted on the CRT device implant procedures and the associated mortalities have produced the following results.
- Implants have been unsuccessful in about 10% of the cases mostly due to the nature of the patients’ challenging anatomy of the coronary veins or the veins of the heart.
- Complications rates due to different procedures can be reduced by the use of different type of lead, known as OTW(over-the-wire) lead.
- Coronary Sinus dissection or perforation is generally resolved without further complication.
- Left ventricular complications, namely dislodging of the leads occurred in 9% of all cases involved in the study
- The time for implant of the device decreases with the experience of the personnel at the centre where implant is done.
Some patients undergoing cardiac resynchronization therapy have a high risk of sudden cardiac death. A special CRT device is available for such patients which can stop potentially life threatening rapid heartbeats by delivering an electric shock down. This device incorporates the principle of a defibrillator In the CRT device and is therefore called a CRTD device, where the D stands for defibrillation.
Ideal Candidates for Cardiac Resynchronisation Therapy
Cardiac resynchronization therapy is the right choice in the following cases:
- Patients having a weakened or enlarged heart muscle.
- Patients experiencing a bundle branch block or a marked electrical delay in the pumping action of the lower chambers.
- Patients suffering from moderate to severe Congestive Heart Failure symptoms even after proper medication and lifestyle changes.