If you have an arrhythmia that causes your heart to beat too fast or too slow, you may feel lightheaded or dizzy. This happens because your heart cannot pump blood effectively during excessively fast or slow heart rates. The ineffective pumping action decreases your blood pressure, reducing the amount of blood that reaches your brain.

The sensation of lightheadedness is a result of this lack of blood flow to the brain. If your blood pressure drops too low, you may feel that you are about to pass out. This sensation is called presyncope. Syncope is the medical term for a temporary loss of consciousness (passing out).

What distinguishes lightheadedness from an arrhythmia?

Dizziness can be caused by conditions other than arrhythmia. For this reason, your health professional will try to determine whether your dizziness is caused by a heart condition, medications, or other factors.

Many of the medications 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, medication-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.