Patient Conditions

Read how Maryland Heart Center cardiologists are treating ventricular tachycardia by using new imaging techniques.


Arrhythmias are abnormal heart rhythms, which cause the heart to beat too fast (tachycardia) or too slow (bradycardia) and to pump blood less effectively.

Arrhythmias are very common, affecting millions of people worldwide. They are the main cause of sudden cardiac death in the United States, accounting for more than 400,000 deaths each year.

Arrhythmias are caused by either a disruption of the normal electrical conduction system of the heart, or heart disease.

Normally, the four chambers of the heart (two atria and two ventricles) contract in a very coordinated manner:Medical illustration of the intrinsic conduction system of the heart

  • The signal for the heart to contract in a synchronized manner is an electrical impulse that begins in the "sinoatrial node" (also called the SA node), which is the body's natural pacemaker.

  • The signal leaves the sinoatrial node and travels through the two atria, stimulating them to contract. Then, the signal passes through another node (the AV node), and finally travels to the ventricles and stimulates them to contract in synchrony.

Problems can occur anywhere along the conduction system, causing various arrhythmias. There can also be a problem in the heart muscle itself, causing it to respond differently to the signal, or causing the ventricles to contract in an uncoordinated manner.

An arrhythmia occurs when:

  • The heart's natural pacemaker develops an abnormal rate or rhythm
  • The normal conduction pathway is interrupted
  • Another part of the heart takes over as pacemaker
  • Disease in the heart muscle allows electricity to travel in a circuit generating a rapid and often dangerous heart rhythm


Many people who have arrhythmias have underying heart disease. They may suffer from coronary artery disease, heart valve disorders, hypertension or other cardiac conditions. Imbalances of blood chemistries may also cause arrhythmias. Arrhythmias however, can occur in patients with no known heart disease.

Arrhythmias can also be caused by some substances or drugs. These include:

  • Antiarrhythmics
  • Beta blockers
  • Psychotropics
  • Sympathomimetics
  • Caffeine
  • Amphetamines
  • Cocaine


Some common symptoms you may experience can include:

  • Sensation of feeling the heart beat (palpitations)
  • Fainting
  • Lightheadedness, dizziness
  • Chest pain
  • Shortness of breath
  • Weakness and fatigue
  • Changes in the rate, rhythm, or pattern of the pulse

This page was last updated: August 26, 2014

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