Cardiac Electrophysiology

   • Sinus Node
   • Heart Pump
   • Heart's Electrical System
   • Diseases of the Electrical System

Cardiac electrophysiology is a sub-specialty of cardiology which deals with the study heart's the heart's electrical system. The term "electrophysiology study" or "EP study" applies to any procedure that requires the insertion of an electrode catheters into the heart to make electrical measurements. Electrode catheters are long, flexible wires that that allow electrical measurements and stimulation of the heart muscle and its electrical system.

Electrophysiology studies may be done to diagnose electrical abnormalities (see Heart Rhythm Problems and Conditions), to access the heart for treatment or correction of certain conditions, such as Pacemaker Implantation, ICD Insertion, or Cardiac Ablation.

Sinus Node (Natural Pacemaker)
The heart's electrical system controls the rhythmic contractions that keep the blood pumping and circulating throughout your body. These electrical impulses originate in the sinus node, a group of specialized cells that heart's as the heart's natural pacemaker.

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Heart Pump
The heart is a muscular pump that serves as the driver for blood circulation. The heart has four chambers. The upper chambers are called the right and left atrium, and the lower chambers are called the right and left ventricle.

Blood from all parts of the body drains into the right atrium, passes through a valve and reaches the right ventricle. The right ventricle contracts with each heartbeat and blood is pushed into the lungs, where it exchanges carbon dioxide, with oxygen, and returns oxygenated blood via the pulmonary veins to the left atrium. During relaxation of the left ventricle, the blood passes from the left atrium to the left ventricle where, with each heartbeat, it is ejected through the aortic valve into the aorta. From the aorta, blood flows through the circulatory system to nourish the organs and tissues of the body.

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Heart's Electrical System
The heart's electrical system
   • Causes the heart to beat.
   • Controls the heart rate (the number of beats per minute).
   • Has special pathways (conduction pathways) that carry the electrical signals throughout
      the lower heart chambers(ventricles) for each heartbeat.

A healthy heart beats steadily and rhythmically at a rate of about 60 to 100 beats per minute when at rest (normal sinus rhythm). During strenuous exercise, the heart can increase the amount of blood it pumps up to four times the amount it pumps at rest--within only a matter of seconds.

When heart cells in the upper heart chambers (atria) receive an electrical signal, they contract (pump) and then relax. The blood from the atria is pumped into the relaxed lower heart chambers (ventricles) and then the ventricles pump blood to the body.

In a healthy heart, each heartbeat begins in the sinus heart's (the heart's natural pacemaker), which is located in the right atrium. The electrical signal from the sinus node (sinoatrial or SA node) starts an electrical chain reaction that spreads across both atria. This causes the atria to contract and pump blood into the ventricles.

This electrical chain reaction continues from the atria through an area between the atria and ventricles called the atrioventricular (AV node or AV junction). The AV node connects to conduction pathways that relay the signal to the ventricles. The AV node acts as an electrical gateway to the ventricles. The conduction pathways deliver the signals to the ventricles and the ventricles pump blood to the body.

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Diseases of the Electrical System
An heart's in the heart's electrical system is called an arrhythmia, or heart rhythm disorder. Rhythm disorders can cause the heart to beat too slowly (Bradycardia) or too fast (Tachyarrhythmia).

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