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Home » Services » ACI Cath Lab » Electrophysiology » Cardiac Rhythm Devices

Cardiac Rhythm Devices


Pacemakers are devices used to treat patients who have an abnormally slow heart beat or bradycardia. The cause of the slow heart beat could be either that there is a problem with heart’s natural starting point for the electrical signals (sinus node) or the conduction pathway from the sinus node is blocked. A pacemaker is used to either replace the function of the sinus node or to bypass blockages in the conduction pathway and thereby restore a more nominal rhythm to the heart beat.

The pacemaker consists of two parts, one part, called the pulse generator, is external to the body and creates the electrical signals. The other part is the leads that carry the tiny electrical impulses into the body and to the heart.

The implantation procedure is relatively simple and is carried out using local anaesthetic and mild seduction usually in a Cath lab. During the procedure the leads are inserted through a tiny puncture in the skin into a vein and guided using X-rays to the heart where it is carefully implanted into the required chamber of the heart. The pulse generator is then placed in a pouch just under the skin and the leads are connected to the pulse generator. The doctor then uses a programmer to turn the pacemaker on.

There are two basic groups of pacemakers and these are either single or dual chamber pacemakers. A single chamber pacemaker sends signals to one chamber of the heart which is usually either the right atrium or right ventricle. A dual chamber pacemaker sends signals to two chambers which are usually the right atrium and right ventricle. The doctor decides which type of pacemaker is required depending on the patient’s condition.

Resynchronization Therapy

In some patients who have developed a condition called heart failure the conduction of electrical signals from the right side of the heart to the left side of the heart becomes disturbed. This can result in a very disorganized and inefficient beating of the heart where both sides of the heart beat independently. Studies have shown that these patients can greatly benefit from a special type of pacemaker device called a biventricular pacemaker.

This device is similar in makeup to the pacemaker devices described above. The leads however are implanted in both the left and right ventricles. The device’s role is to restore the coordination of the heart beat in the left and right sides of the heart.

Implantable Cardioverter Defibrillator (ICD)

As described in FAQ section, the irregular heart beat called ventricular fibrillation is a potentially fatal arrhythmia if it is not treated within minutes of its onset. The main treatment is defibrillation or cardioversion and is usually performed by applying a large electrical voltage to the patient’s chest. This large external electrical impulse has the effect of overwhelming the electrical pathways in the heart and thereby resets the normal electrical rhythm of the heart. This effectively stops the chaotic electrical short circuit that resulted in the ventricular fibrillation.

The problem is however that the underlying condition of the heart is still the same and therefore the ventricular fibrillation may recur.

In such patients who are at risk for recurrent ventricular fibrillation there is now an implantable device called an implantable cardioverter defibrillator (ICD) which can save the patient’s life. The implanted ICD senses the fibrillation event and automatically providing an electrical voltage directly to the patient’s heart thereby restoring a more normal heart beat.

The ICD device is slightly larger than a pacemaker though modern versions are almost the same size. It is implanted in a Cath lab in a similar procedure to that described for the pacemaker above.

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