Biventricular cardiac pacemaker

Biventricular cardiac pacemakers, also known as cardiac resynchronisation therapy (CRT), refers to surgically implanted cardiac conduction devices with one lead in each ventricle (and generally one into the right atrium). 

Components

•  lead in the right atrium
•  lead in the right ventricle
•  lead in the coronary sinus to pace the left ventricle

Function

Cardiac resynchronisation therapy is used generally in patients with severe heart failure who are not controlled well on maximal medical therapy and who have a prolonged QRS duration on ECG (i.e. bundle branch block). In bundle branch block, the affected conduction bundle delays conduction of the depolarisation wave and thereby delays ventricular contraction. This means, for example, in left bundle branch block the left ventricle will contract after the right, resulting in a broad QRS complex. Pacing leads are implanted into both ventricles and the device generates electrical impulses in order to stimulate both ventricles to contract simultaneously (and thereby improve the patient's symptoms and functional status).

Differential diagnosis

It should not be confused with other implantable devices in the chest like such as:

• vagal nerve stimulator
• automatic implantable cardioverter defibrillators (AICD)