Electrophysiology, or EP, is the branch of cardiology that deals with the electrical system of the heart including rhythm disturbances, called arrhythmias. The normal electrical or conduction system includes a natural pacemaker called the SA (sinoatrial) node that sends impulses to the AV (atrioventricular node) which then distributes the electrical charge to the main pumping chambers of the heart via the bundles. A malfunction or short circuit at different locations along the conduction system can lead to fast arrhythmias known as tachycardias, or slow arrhythmias, known as bradycardias.
Holter monitors and event monitors record your heartbeat during daily activities. The Holter monitor records all your heartbeats, usually over a 24-hour period. Event monitors record selected rhythms that correlate with your symptoms, usually over a two week interval. Both monitors are roughly the size of a calculator. The monitors are often ordered for complaints of palpitations, dizziness, or passing out.
Cardioversion is the inpatient procedure attempting to convert an irregular heart rate, usually atrial fibrillation or atrial flutter, to a normal rhythm, either with medication or an electrical shock. A light anesthesia is given during electrical cardioversions. Following cardioversion, your physician may elect to start new antiarrhythmic drug therapy that may require several days of inpatient monitoring. Atrial fibrillation and atrial flutter are “quivering” rhythms of the upper heart chambers. If they persist beyond 48 hours, they require several weeks of anticoagulation with Coumadin to reduce the risk of stroke before cardioversion is attempted.
Permanent pacemakers are placed for bradyarrhythmias (slow heart rates). Sometimes the pacemaker completely controls the heart rhythm, at other times it only serves as a backup for slow rates. Pacemakers consist of two parts: the generator and the lead(s). The generator stores the pacemaker battery. It is roughly the size of a silver dollar and is usually surgically inserted under the skin near the collarbone. One or two thin wires, called leads, are threaded through the veins to the right heart chambers under x-ray guidance. After 5-8 years, the battery may deplete, requiring a new generator. The leads are usually left intact. Some restrictions are placed on you for a few weeks after a pacemaker insertion to allow the wound to heal and the leads to settle in place; then you can resume usual activities.
Several of the procedures listed below require the skills of a highly trained cardiologist, the electrophysiologist.
A sudden loss of consciousness is termed syncope (passing out). Two of the more common cardiac causes of syncope include arrhythmias and a condition known as neurocardiogenic syncope. The latter term describes abnormal nerve firings from the brain that lower blood pressure and heart rates leading to a sudden blackout spell.
Tilt table testing is used to assess neurocardiogenic syncope. An adrenaline type medicine is infused intravenously while you are strapped to a table that is raised to an 80 degree angle. A positive test will reproduce your symptoms. Tilt table testing is safe; it is often done in the office.
The electrophysiology study (EPS) is the electrical equivalent of cardiac catheterization. Catheters are inserted through the groin veins into various regions of the heart. These catheters can both sense electrical impulses and deliver electrical stimuli to reproduce various arrhythmias. The procedure is especially useful for sustained arrhythmias, as part of syncope workups, and for evaluation of cardiac arrest. Following an EPS, your physician may recommend medication, a pacemaker, an implantable defibrillator, or radiofrequency ablation.
Implantable defibrillators (ICD’s) (photo above) are similar to pacemakers except they function to shock the heart during tachyarrhythmias, such as ventricular tachycardia or ventricular fibrillation. If left alone, these fast heart rates from the bottom chambers of the heart (ventricles) can be lethal. The newer defibrillators now also include a backup pacemaker.
Radiofrequency Ablation (RF) is sometimes performed in conjunction with an electrophysiology study. Certain arrhythmias can be cured or greatly reduced in frequency by the application of radio-frequency energy through a catheter. A small scar is created in the heart; this usually does not cause problems. Occasionally a pacemaker is required after an ablation.
Patient Preparations for cardioversion, pacemakers, tilt tables, EPS, defibrillators, and ablations: