A pacemaker is a small device that helps control your heart beat by providing low-energy electrical pulses that keep the heart beating normally. Pacemakers are similar to defibrillators, but they only provide low-energy shocks and are unable to restart the heart with high-energy shocks.
The device consists of two parts:
Lead wires (electrodes)
The pulse generator contains a battery and a small computer that regulates the rate of electrical pulses sent to your heart and leads (electrodes) with insulated wires which are placed in a chamber, or chambers of your heart and deliver the electrical impulses to adjust your heart rate.
Pacemakers can have one, two, or three wires; your doctor will decide which kind of pacemaker you need based on your specific condition. Your doctor will implant the device by making a pocket in the tissue under your skin to hold the pacemaker and then threading the wires into a vein and guiding them to the right place in your heart. The wire count is defined as:
One wire: single chamber
Two wires: dual chamber
Biventricular pacemaker is a special pacemaker, which is used to synchronize the contractions of the left ventricle with the right ventricle, to improve the ejection fraction in patients with severe and moderately severe symptoms of heart failure.
Ejection fraction is a measure of blood that is pumped out by the left ventricle of the heart and is expressed in percentage. A normal ejection fraction usually lies between 50% and 70%. A patient with heart failure has a low ejection fraction, hampering the blood supply to various parts of the body and leads to symptoms of heart failure that include shortness of breath, dry cough, swelling of the ankles and legs, weight gain, increased urination, fatigue and rapid or irregular heart-beat.
Biventricular implantation is considered in heart failure patients with:
Severe or moderately-severe heart failure symptoms
Delayed electrical activation of the heart
Either a risk or history of cardiac arrest
On long-term medications for heart failure
Similar to a standard pacemaker, a biventricular pacemaker can be implanted either by an endocardial (transvenous) approach or an epicardial approach. However, a biventricular pacemaker usually has three leads, one is guided to the right ventricle, one to the left ventricle and the third (which is not always present) is guided to the right atrium. The lead in the left ventricle is guided through the coronary sinus.
When the heart rate drops below the rate set with the pacemaker, it senses the drop and transmits electrical impulses to the left as well as the right ventricle to contract simultaneously, improving the ejection fraction and the cardiac function. The lead placed in the right atrium helps the heart to function in a more balanced way.
Biventricular pacemaker implantation is also called cardiac synchronization therapy and is only a part of any comprehensive heart failure management program. Medications, life style changes and regular follow up with a cardiac specialist are all crucial for managing the symptoms and improving the quality of life in heart failure patients.