Basic Facts

Arrhythmias are caused by problems with the heart's electrical system, such as abnormal formation of the electrical impulses that begin heartbeats or by a disruption of the pattern of conduction of those impulses.

Because the ventricles are primarily responsible for moving blood through the body, ventricular arrhythmias are often more serious than other arrhythmias.

An arrhythmia is a change in the heart's normal rate or rhythm. Typically, the heart beats with a regular rhythm at a rate between 60 and 100 beats per minute. Problems with the heart's electrical system or the heart's response to the electrical signal can interrupt the heart's coordination and cause arrhythmias.

Ventricular arrhythmias are abnormalities that affect these ventricles, or lower chambers of the heart. There are two types of ventricular arrhythmias, disorders of impulse generation and disorders of impulse conduction. With disorders of impulse generation, the heart beat originates in a place other than the sino-atrial node, the heart's natural pacemaker. With disorders of impulse generation, the electrical impulses are partially or completely prevented from traveling their normal pathway.

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Ventricular arrhythmias include:

Ventricular tachycardia

An electrocardiogram of an episode
of sustained ventricular tachycardia.

• Premature ventricular complexes (PVCs), which are premature heartbeats;
• Ventricular tachycardia, an abnormally fast heartbeat; and
• Ventricular fibrillation, in which the heart quivers rather than contracts.

Ventricular fibrillation is a medical emergency that requires immediate attention.

WHAT ARE THE SYMPTOMS?

Some ventricular arrhythmias have no symptoms. When symptoms do occur, they include:

Ventricular fibrillation

An electrocardiogram reflecting the
irregular, pulseless electrical activity
of ventricular fibrillation.

• Diminished or irregular pulse;
• Fatigue;
• Shortness of breath;
• Fainting (syncope);
• Palpitations (awareness of one's own heartbeat);
• Low blood pressure;
• Chest pain; and
• Cardiac arrest.

CAUSES AND RISK FACTORS

Causes of ventricular arrhythmias include:

• Abnormal electrolyte (mineral, such as potassium and magnesium) levels in the blood;
• Electrocution;
• Heart attack (myocardial infarction);
• Scarring resulting from a heart attack; and
• Unstable angina (chest pain).

The cause of some ventricular arrhythmias is unknown.

Risk factors for ventricular arrhythmias include:

• Alcohol abuse;
• Cardiomyopathy (enlarged heart);
• Congenital heart defects;
• Drug use, including caffeine, cocaine, some heart drugs, diet pills, and some cold and allergy medications;
• Coronary heart disease;
• Hypertension (high blood pressure); and
• Valve diseases.

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DIAGNOSIS

The physician will take a detailed medical history and perform a physical examination, during which he or she may hear irregular heartbeats with a stethoscope. The physician may also order tests, including an electrocardiogram (ECG), either resting or ambulatory (using a portable machine called a Holter monitor or a loop recorder). The physician may also order electrophysiology testing.

TREATMENT APPROACH

Many cases of arrhythmias may not require treatment. Other arrhythmias can be treated by treating any underlying heart disease. Treatments for ventricular arrhythmia includes:

• Defibrillation;
• Medication (beta-blockers and antiarrhythmic agents);
• Radiofrequency catheter ablation;
• Angioplasty; and
• Pacemaker implantation.

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