How effective is an ECG for a heart attack?

It records the heart's electrical activity through sensors placed on the skin. Changes in the tracing can show that part of the heart muscle may not be receiving enough blood, help identify a serious type of heart attack, and guide urgent treatment.

A clear abnormal pattern can support a heart-attack diagnosis, especially when it matches symptoms and examination findings. A normal or uncertain tracing does not safely rule out a heart attack: electrical changes may be subtle, develop over time, or affect areas that are not obvious on the first recording.

For this reason, a medical team may repeat the ECG and combine it with blood tests that look for heart-muscle injury, monitoring, and sometimes imaging or a procedure to examine the heart arteries. The ECG is useful because it is quick and does not require needles or radiation, but its result must be interpreted in context.

Treat possible heart-attack symptoms as an emergency rather than waiting to arrange an ECG yourself. Call emergency services if there is pressure, tightness, squeezing, or pain in the chest, particularly with breathlessness, sweating, nausea, faintness, or discomfort spreading to the arm, back, neck, or jaw.

While waiting, stop exertion and sit in a supported position. Do not drive yourself to hospital. Emergency clinicians can perform an ECG promptly, assess your vital signs, and decide which further tests and treatments are needed.

Seek emergency help immediately for new or severe chest discomfort, chest discomfort that lasts or returns, or symptoms with shortness of breath, collapse, marked weakness, or a cold sweat. Symptoms can be less typical in some people, including older adults and people with diabetes, so unexplained breathlessness, nausea, or sudden unusual fatigue also deserves urgent assessment.

Do not use a normal home reading, a previous normal ECG, or temporary symptom relief as reassurance. A clinician needs to decide whether repeat recordings and additional tests are required.

You could ask: What did my ECG show, and does it match my symptoms? Do I need a repeat ECG or blood tests? Which warning symptoms should make me return immediately? If the ECG is normal, what other causes or tests will you consider?