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Heart Rhythm Problems: Symptoms - Topic Overview

When is lightheadedness not caused by an arrhythmia?

Dizziness can be caused by conditions other than arrhythmia. For this reason, your doctor will try to find out whether your dizziness is caused by a heart condition, medicine, or other things.

Other causes of lightheadedness include hyperventilation, panic or anxiety attacks, prolonged standing, and excessive fluid loss caused by problems such as vomiting or diarrhea.

Many of the medicines used to treat heart conditions, such as beta-blockers, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, and diuretics, can lower the blood pressure excessively and result in lightheadedness. In general, medicine-induced lightheadedness frequently occurs soon after you stand up because of a drop in blood pressure that happens when you stand (orthostatic hypotension). In contrast, lightheadedness due to an arrhythmia can occur even when you are sitting or reclining.

Fainting (syncope)

Syncope (say "SING-kuh-pee") refers to a sudden loss of consciousness that doesn't last long. Syncope may be the first sign that you have an arrhythmia. And it is a very worrisome symptom for several reasons:

  • Fainting can result in a serious injury (for example, if you faint while climbing stairs or driving).
  • You faint because your brain did not get enough oxygen to function, which may be a warning sign that you have a serious medical condition.

An arrhythmia can cause syncope in the same way that it causes lightheadedness (presyncope). Your heart cannot pump blood effectively during excessively fast or slow heart rates, reducing the amount of blood that reaches your brain. With syncope, though, the arrhythmia causes such a dramatic drop in the blood pressure that the brain doesn't receive enough blood to keep you awake. So you lose consciousness. For an arrhythmia to cause syncope, your heart rate must be extremely fast or extremely slow, or you must also have some other heart condition.

How long does syncope last?

It is important to recognize that syncope is transient, meaning that you wake up soon after fainting. Consciousness may return because the arrhythmia spontaneously stops and a normal heart rhythm and blood pressure return. Even if the arrhythmia persists, you may still regain consciousness. When you have an episode of syncope due to an arrhythmia, it typically happens while you are standing or sitting, and the loss of consciousness causes you to fall to the floor. After you are lying down, blood flow returns to your brain, even though your blood pressure may remain low. When adequate blood flow returns to your brain, you will likely wake up.

What are the risks associated with passing out from an arrhythmia?

Fast or slow arrhythmias may cause you to pass out. Depending on your position and activity at the time of the episode, you may seriously injure yourself. If you are standing up at the time of the arrhythmia, you may pass out and fall. The fall may cause you to injure your head, break an arm or leg, or receive other injuries. If you are driving, you may crash, causing severe injury to yourself and anyone else involved.

Passing out may be a sign that you are at risk for a life-threatening arrhythmia. If you have symptoms of an arrhythmia that may cause you to pass out, do not drive any vehicle until your condition has been evaluated and treated.

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WebMD Medical Reference from Healthwise

Last Updated: August 09, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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