For the heart to pump, some electrical signals have to flow through the heart. This is done in a highly organized manner, through a network of specialized cells (called ‘Conduction system’), designed to conduct electrical impulses. When this conduction system malfunctions, it results in the heart beating either very fast, very slow or irregularly, depending on the type of abnormality. These conditions are called cardiac arrhythmias (abnormal cardiac rhythms). Because of this heart condition, patients may experience symptoms like palpitations, dizziness and blackouts, fatigue, etc. Sometimes these abnormalities result in significantly impaired blood supply to vital organs of the body, like brain, kidneys, etc., resulting in unconsciousness, stroke, kidney failure, etc. and can even be fatal. Luckily, most of these conditions are fully curable, while some of them can be well controlled (with medicines and/or invasive procedures), thereby making patients lead a normal life.
The specialty that deals with these abnormalities is called Cardiac Electrophysiology.
Cardiac arrhythmias may be of two types: Tachycardia and Bradycardia.
Tachycardia is a cardiac arrhythmia condition in which the heart rate is abnormally fast. Tachycardia may be classified as Ventricular Tachycardia (VT) or Supraventricular Tachycardia (SVT) and these may be atrial fibrillation, atrial tachycardia, AV nodal re-entrant tachycardia (AVNRT) or atrioventricuar reciprocating tachycardia (AVRT). These occur as a result of either short-circuiting of electrical conduction due to presence of an abnormal conduction tissue or due to misfiring of extra impulses from one of the chambers of the heart.
Bradycardia is a cardiac arrhythmia condition in which the heart beats too slow to maintain a regular circulation. Bradycardia may occur as a result of abnormality of sinus node and/ or an AV node. Thus, either the impulse production is slowed down or there is obstruction to the flow of these electrical impulses along the conduction system.
For patients with tachycardia, a complete electrophysiological study is done, in which multiple leads (wires) are inserted from the groin (mostly under local anesthesia, without any incisions) into the various chambers of the heart. Then ECG from inside the heart is recorded with the help of these wires using a special mapping system. Tachycardia is then induced by pacing various chambers of the heart and by injecting some medicines, if required. By studying these signals, the source of abnormal electrical activity can be pin-pointed. To treat this abnormality, radiofrequency waves are delivered at the site of abnormality. This heats up and destroys the abnormal tissue. Care is taken to avoid damage to the normal conduction tissue. This procedure is called as Radiofrequency ablation. It is by and large a safe and painless procedure and results in a permanent cure in more than 98% of the cases. The patient remains conscious throughout the procedure and can be discharged within 24 hrs.
If the patient’s heart rate is too slow (bradycardia), it may be increased by electrical stimuli from a device called a pacemaker. A pacemaker consists of:
Pacemaker implantation is by and large a safe procedure, performed mostly under local anesthesia. The patient remains awake during the entire procedure and can be discharged within 48 hours.
This is a special type of pacemaker that detects if the heart rate goes abnormally high, to dangerous, life-threatening levels. If so, it treats this high heart rate either by transiently rapidly pacing the heart or by delivering D/C shock, thereby preventing sudden cardiac death.
In certain cases of heart failure, a special type of multi chamber pacemaker (heart failure device) or cardiac re-synchronization therapy (CRT) can be used. By this procedure, the different chambers of the heart which have become asynchronous (due to enlargement) are stimulated simultaneously or in quick succession, thereby establishing synchronicity of contraction between various segments of the heart and effectively improving cardiac output (amount of blood pumped out of the heart).