Friday, 12 January 2018

Pacing modes of Pacemaker

Pacemaker is a device which uses electrical impulses delivered by electrodes to maintain and regulate the beating of heart-so the primary function of pacemaker is to maintain adequate heart rate. When a condition called ‘heart block’ occurs, the electro conduction system of heart is interrupted and heart’s ability to pump blood is weakened. In such cases physicians normally use pacemakers to stimulate the heart. Pacemaker is an electrical generator that delivers the wanted pulse at an approximate time. Modern pacemakers are externally programmable and allow the cardiologist to select optimum pacing modes for individual patients.

Modern pacemakers usually have multiple functions. The most basic function is to monitor the heart’s native electrical rhythm. When the pacemaker fails to sense a heartbeat within a normal beat-to-beat time period, it will stimulate the ventricle of the heart with a short low voltage pulse. This sensitivity and stimulating activity continues for each heart beat. Different pacing modes can be adopted depending on the condition of patients. Some pacemakers are external and are worn on belt and some others are placed at the bed side. Some others are surgically implanted. Some of the pacing modes of pacemaker are explained below.

1. Transcutaneous Pacing (External Pacing): This procedure is performed by placing two pads on the patient’s chest. Then a suitable pacing rate is selected and the pacing current is gradually increasing until electrical capture is achieved. External pacing is an emergency procedure and should not be relied upon for a long period of time.

2. Epicardial pacing (temporary): This mode of pacing is used during open heart surgery. Here the electrodes are placed in contact with the outer wall of the ventricle (epicardium) to maintain satisfactory cardiac output.

3. Tran-venous pacing: It is an alternative to transcutaneous pacing. Here a pacemaker wire is placed into the vein under sterile condition and then passed into either the right atrium or right ventricle. The pacing wire is then connected to an external pacemaker outside the body.

4. Permanent pacing: There are three basic types of permanent pacemakers based on the number of chambers occupied and their vital operating mechanism. They are Single chamber pacemaker, Dual chamber pacemaker and Rate responsive pacemaker.