A stroke, sometimes called a “brain attack,” occurs when blood flow to a part of the brain is disrupted, either by a blockage or a bleed. This interruption deprives brain cells of oxygen and nutrients, causing them to die within minutes. An electrocardiogram, or ECG, is a separate and common medical test that records the heart’s electrical activity. It uses small electrodes placed on the skin to measure the speed and rhythm of the heartbeat. An ECG is a standard tool used by medical professionals when a stroke is suspected or has been confirmed.
Using an ECG to Find the Cause of a Stroke
An electrocardiogram is frequently used to investigate the cause of a stroke, particularly an ischemic stroke resulting from a blockage. A primary condition an ECG can identify is atrial fibrillation (AFib), a type of irregular and often rapid heart rhythm. AFib is a major risk factor for stroke, increasing a person’s risk by up to five times.
In a heart with atrial fibrillation, the upper chambers (atria) beat chaotically and out of sync with the lower chambers. This irregular contraction prevents blood from being fully pumped out, allowing it to pool. When blood pools, it can form clots that may travel through the bloodstream to the brain, blocking an artery and causing a stroke.
The ECG is a primary diagnostic tool for detecting atrial fibrillation, as its characteristic appearance helps clinicians identify the arrhythmia. This is important because AFib can be asymptomatic and previously undiagnosed. An ECG might also reveal other issues, such as evidence of a recent heart attack, that could be a source of blood clots.
How a Stroke Can Change the Heart’s Electrical Activity
The connection between the brain and heart is a two-way street; a stroke can directly impact the heart’s function. This phenomenon is known as cerebrocardiac syndrome or stroke-heart syndrome. It describes cardiac complications, including ECG abnormalities, that can occur after a stroke, even in individuals with no prior heart disease.
This response is driven by the brain’s influence over the autonomic nervous system, which regulates heart rate and rhythm. Strokes affecting specific brain regions like the insular cortex can disrupt this system. Damage to the insular cortex can lead to an imbalance between the sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) signals sent to the heart.
This neurological disruption can trigger a surge in stress hormones like catecholamines, which directly affect cardiac cells. The result can be a range of electrical disturbances in the heart, including changes in its rhythm or how the muscle cells recharge after each beat. These changes are a direct consequence of the brain injury.
Specific ECG Abnormalities in Stroke Patients
ECG analysis after a stroke looks for two categories of findings. The first is a potential cause of the stroke, most commonly atrial fibrillation. On an ECG, AFib appears as an “irregularly irregular” rhythm where the spacing between heartbeats is unpredictable, and the normal P waves are absent.
The second category includes changes caused by the stroke’s impact on the brain. Common findings include T-wave abnormalities, such as deep, inverted T-waves called “cerebral T-waves.” Other changes are QT interval prolongation, indicating the heart’s ventricles are taking longer to recharge, and prominent U waves. These stroke-induced patterns can sometimes mimic a heart attack, requiring a comprehensive clinical evaluation.
Cardiac Monitoring After a Stroke
A single ECG captures only a few minutes of heart activity and may not be sufficient to detect intermittent rhythm problems. Atrial fibrillation, a leading cause of stroke, is frequently intermittent. This means a person’s heart rhythm can switch between normal and irregular, making it easy to miss on a brief test.
To address this, long-term cardiac monitoring is often recommended. A common tool is the Holter monitor, a portable device that continuously records the heart’s electrical activity for 24 to 72 hours or longer. Guidelines recommend monitoring for at least 24-72 hours after a stroke to effectively screen for AFib.
For longer-term surveillance, providers might use event monitors or implantable loop recorders. An implantable loop recorder is a small device placed just under the skin of the chest that can monitor the heart’s rhythm for up to three years. This monitoring helps detect arrhythmias to ensure correct preventive treatment is prescribed to reduce future stroke risk.