The Heart's Electrical System

Your heart is a muscle that works like a pump. The main job of your heart is to pump blood  throughout your body. The heart is divided into a right and left side. Each side has an upper chamber (atrium), which collects blood returning to the heart, and a muscular lower chamber (ventricle), which pumps the blood away from the heart.

Medical illustration of a heart showing the left and right atria, which collect blood returning to the heart, and the left and right ventricles, which pump the blood away from the heart.

The pumping of your heart is regulated by an electrical current or impulse, much like a spark plug in a car. The electrical impulse starts in the sinoatrial (SA) node, often called the body’s natural pacemaker, and then spreads throughout both atria, like ripples in a pond. This causes both atria to contract, which squeezes blood into the ventricles.

The impulse then travels down to the atrioventricular (AV) node, which is like a wire that connects it to the ventricles. The AV node splits into two branches, allowing the electrical signal to spread evenly to both ventricles at the same time. This is what causes your heart to beat effectively.

Medical illustration of a heart showing the sinoatrial node, the atrioventricular node, and the left and right bundle branches, which control the electrical impulse that causes your heart to pump.


Heart Arrhythmias

Any disruption in the usual electrical pathways in your heart can cause an abnormality in your heart rhythm. This is called an arrhythmia.

Supraventricular Arrhythmias

Abnormal heart rhythms that begin in the upper chambers of the heart are usually rapid. People who experience supraventricular arrhythmias may feel dizzy or light-headed, or have chest tightness or palpitations. Some people do not have any symptoms at all.

Supraventricular arrhythmias can last for only a few seconds or for prolonged periods of time. In general, they are usually not life threatening. However, they can disrupt the regular flow of blood throughout your body and cause you to feel unwell or have other, more serious, symptoms.

Types of Supraventricular Arrhythmias


Atrial fibrillation is an irregular heart rhythm that occurs when the SA node does not generate normal electrical impulses. Instead, the atria start to trigger rapid and disorganized electrical signals, causing the atria to quiver rather than contract normally. These abnormal impulses randomly pass through to the ventricles, resulting in an irregular and inefficient heartbeat.


Atrial flutter is similar to atrial fibrillation but less common. In atrial flutter, the electrical impulse that starts in your atria gets disrupted, interrupting its normal flow to the AV node. This creates a circular feedback loop and sets off a series of rapid-fire impulses, causing your heart to beat quite fast for periods of time. Patients with atrial flutter often also have atrial fibrillation.


Tachycardia is a rapid heart rhythm that occurs when there is a disruption in the normal electrical pathways. There are various types of supraventricular tachycardias.

  • Atrial Tachycardia: With atrial tachycardia, the electrical impulse starts somewhere in the atria other than the SA node. This causes an abnormally rapid heart rate.
  • AV Node Re-entrant Tachycardia: AV node re-entrant tachycardia occurs when the electrical impulse gets caught up in extra fibres around the AV node and starts to rapidly circle the AV node. This causes a rapid heart rate.
  • AV Re-entrant Tachycardia (AVRT)/Wolff-Parkinson-White (WPW) Syndrome: People with AVRT/WPW syndrome were born with an extra electrical pathway in their heart that connects the atria and the ventricles, but completely bypasses the normal AV node pathway. When the electrical impulse goes through the extra pathway, it can cause periods of very rapid heartbeats.

Ventricular Arrhythmias

Ventricular arrhythmias occur in the lower part of the heart and can be a bit more dangerous. During ventricular tachycardia, the heart beats so fast that it cannot properly pump blood to the rest of the body. This can cause extreme dizziness, fainting or sometimes a complete collapse.

Diagnosing and Treating Heart Arrhythmias

Electrophysiology Study/Standard Ablation

In order to fully understand and treat your heart arrhythmia, your doctor has recommended an electrophysiology (EP) study.

An EP study is a specialized procedure that allows your doctor to have a detailed look at the electrical signals in your heart and pinpoint the source of any abnormal rhythms. EP studies use soft catheters with tiny electrodes at their tips to map and evaluate the electrical activity inside your heart. The wires are inserted through veins in your groin or, occasionally, in your neck and threaded up to the inner chambers of your heart.

During the procedure, your doctor records and measures your heart’s electrical pathways and may even use tiny electrical pulses to stimulate the arrhythmia so that it can be fully evaluated. Your doctor may also give you different medications through your intravenous (IV) line to see how they affect the arrhythmia.

Risks of EP Studies/Standard Ablation

EP studies and standard ablation procedures are considered to be very safe; however, with any invasive procedure, there can be complications.

Rare complications include:

  • Excessive bleeding where the catheters were put in
  • Bruising or swelling

Very rare complications:

  • The heart or lung can be punctured.
  • Disruption of the heart’s electrical system
  • Blood clot inside the vein
  • Heart attack or stroke

During the procedure and throughout the recovery period, we will be monitoring you closely.

Standard Catheter Ablation

Catheter ablation is done much the same way as an EP study. In fact, most standard catheter ablations are done immediately after the EP study. It involves threading a thin catheter through the veins in your groin up to the areas inside your heart where the abnormal electrical disruptions are occurring.

The tip of the ablation catheter is directed toward the precise location. Once properly positioned, it delivers a small radio-frequency electrical current to burn out the tiny malfunctioning areas.

Usually, the EP study and ablation procedures are pre-planned to occur at the same time. In other cases, the decision to go forward with ablation is not decided until you have had the EP study and your doctor has determined that an ablation is the best treatment option for you.

Standard EP studies or ablations are usually considered day procedures. You will come in on the morning of the procedure and go home at the end of the day. The actual procedure itself may take anywhere from one to four hours to complete.

Before coming in for your procedure, your doctor will discuss any special tests or other preparations that may need to be done.

Conditions Treated with Standard Catheter Ablation

  • Typical atrial flutter
  • AV re-entrant tachycardia (AVRT)/Wolff-Parkinson-White (WPW) syndrome
  • AV node re-entrant tachycardia