The heart’s natural pacemaker is called the sinoatrial (SA) node and, in a healthy heart, the electrical pulse generated at the SA node travels to the atrioventricular (AV) node and down through the bundle of His (also known as the atrioventricular bundle) to the ventricles. Individuals who suffer from bradycardia, which is an abnormal heart rate below 60 beats per minute, have a defective SA node and require the assistance of an artificial pacemaker for healthy heart function. Bradycardia can also result from a blockage in the heart’s conduction pathway that ranges from partial to full inhibition of the electrical impulse. In either case, an artificial pacemaker is used for diagnosing cardiac arrhythmia and paces the heart as necessary. Cardiac Resynchronization Therapy-Pacemakers (CRT-Ps)
CRT-P devices are modified pacemakers that are capable of regulating the rhythm of both the left and right ventricles of the heart. This bi-ventricular pacing is necessary when heart contractions are out of sync, resulting in insufficient blood flow to the body. To regulate the rhythm of the left ventricle, CRT devices use a third lead, known as a left ventricle (LV) lead.
CRT-D devices are similar to CRT-P devices, but have the capabilities of an implantable defibrillator. CRT-D devices are very popular, partly because they have the capability to deal with most types of arrhythmias and can act as a defibrillator in case of a sudden cardiac event.
The primary disadvantages of cardiac resynchronization therapy devices are their high cost and shorter battery lifespan. This has limited the popularity of CRT-P devices, as they are far more expensive than equivalent pacemaker products.