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Electrophysiology

is a highly specialized field of cardiology which deals with rhythm and rate related abnormalities of the heart. The heart has its own spontaneous rhythm and beats regularly at about 60 to 80 times per minute at rest. It increases appropriately with exertion and emotions such as anger and excitement and decreases naturally during sleep. This rhythm results from a regular synchronous electrical activity within the heart and any disturbance in it, for instance, inappropriately fast or slow heart rate or irregular rhythm is called cardiac arrhythmia.

Patients with cardiac arrhythmias have varied complaints. Common ones being abrupt palpitations, lightheadedness or head reeling leading to falls, loss of consciousness, choking sensation, extreme fatigue and even sudden cardiac arrest. Some arrhythmias may be potentially fatal but most often they cause significant symptoms without having to be life-threatening consequences. Rhythm disorders can also cause cardiac pump dysfunction and heart failure if persistent for a long time. Patients with irregular rhythms run the risk of suffering strokes or paralysis attacks. Cardiac arrhythmias are poorly tolerated by patients with pre-existing heart dysfunction (eg. patients with previous heart attacks). Early medical attention should be sought in such cases.

Investigations and Treatment
Cardiac arrhythmias are primarily diagnosed by an ECG. Other tools like Bolter monitoring, echocardiogram, cardiac MRI etc. may add significant value. An electrophysiology study is a specialized diagnostic procedure performed by an electrophysiologist who is a trained expert in cardiac rhythm disorders. In an EPS flexible cables are introduced into cardiac chambers via the route of veins usually from groin or neck. These cables have electrodes at their tips which record the electrical activity of the heart (similar to ECG). Visual analogues of these electrical signals are displayed on monitors and used to diagnose various arrhythmias. EP study guides treatment which includes modalities like radio-frequency ablation (RFA), pacemakers, implantable defibrillators etc. for relief of distressing symptoms to the prevention of cardiac arrest. Sophisticated techniques like 3D guided mapping cardiac mapping, biventricular and His bundle pacing have revolutionized the field in the last decade.

As any other medical field, cardiac electronic devices like pacemakers, implantable defibrillators (ICD) and cardiac resynchronisation therapy (CRT) have seen some remarkable advancements in the last few years and become an integral part of contemporary cardiac care. The devices comprise of a pulse generator implanted under the subcutaneous fat below the collar bone. One or more leads that are connected to the device are positioned in the appropriate chambers in the heart via a vein. The procedure is usually carried out under local anaesthesia.

Pacemakers Demystified
A pacemaker as the name suggests is implanted in patients with abnormally slow heart rates causing symptoms. The heart rate is normally dictated by its natural pacemaker whose electrical impulses are transmitted to the pumping chambers via an intricate conduction system. This electrical system is analogous to a switch and wiring. Failure in any of these components results in bradycardia (slowing of heart rate). Symptoms of bradycardia may range from exertional fatigue or shortness of breath to cardiac arrest. There are different types of pacemakers. The choice of one depends on the site of slowing in the heart, the cardiac function, age and comorbid status of the patient. The inception of the conduction system pacing or physiological pacing lately is revolutionizing the functionality of pacemakers.

Who needs an ICD ?
ICD is implanted in a patient who has survived a sudden cardiac arrest (SCA) or is at risk for one. SCA is the result of a malignant rhythm abnormality called ventricular tachycardia. Patients with prior heart attacks or cardiac pump dysfunction of any cause are vulnerable to SCA. ICD like a watchman constantly monitors the cardiac rhythm and intervenes when necessary. It terminates threatening or fatal arrhythmias by pacing the heart faster or delivering a timely shock.

Is CRT the right device for you ?
A subgroup of patients with severe cardiac pump dysfunction and heart failure Are eligible for cardiac resynchronization therapy. Well-selected patients show an improvement in exercise capacity and cardiac function in weeks to months after implantation. CRT D is a combination of CRT and ICD and combines the benefit of both the devices.

All patient with cardiac devices is advised at least a biannual check. Some may need more frequent visits. The pulse generator is usually replaced every 8 to 12 years with a minor procedure. When used in appropriate patients these devices may be life-saving or changing.

Dr. Soumen Devidutta
MD. DM (Cardiology, AIIMS) PDF in Electrophysiology and pacing PDF in Interventional cardiology,
Cardiologist & Electrophysiologist,
Apollo Hospitals, Jubilee Hills, Hyderabad, India

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