Electrocardiograma (ECG/EKG)

An electrocardiogram — abbreviated EKG or ECG — records the electrical signals that make your heart beat. Ten small adhesive sensors are placed on your chest, arms and legs, and the machine turns the signals it picks up into the familiar tracing of waves. It is painless, involves no electricity entering your body, and the recording itself takes about a minute.

Despite how quick and inexpensive it is, an EKG remains one of the most informative first tests in cardiology. It is often the first thing done when a heart problem is suspected, and it is a standard part of a new cardiology evaluation.

• Rhythm problems — atrial fibrillation, flutter, a heart rate that is too fast or too slow
• Conduction problems — heart block and delays in the heart's wiring, such as a bundle branch block
• Evidence of a heart attack, either happening now or one that occurred in the past
• Signs of a thickened or enlarged heart chamber
• Strain from high blood pressure or a heart valve problem
• Effects of certain medications or of abnormal potassium and other electrolytes

You lie down and a technician places the sensors, which may require clearing small areas of chest hair so they make good contact. You will be asked to lie still, relax your arms and breathe normally for the few seconds the tracing is captured, because movement and shivering blur the signal. The sensors are then peeled off. There are no restrictions afterward and nothing to recover from.

A standard EKG is a snapshot of roughly ten seconds. If your symptoms come and go — palpitations that last a minute, occasional dizziness — the recording can easily be normal simply because nothing was happening at that moment. A normal EKG does not rule out an intermittent rhythm problem, which is exactly why longer recordings exist: an external monitor worn for days or weeks, or an implanted loop recorder for symptoms that are rarer still.

A cardiologist interprets the tracing in the context of your symptoms, your history and any previous EKGs on file — a comparison is often more revealing than a single tracing on its own, which is one reason prior records are worth requesting.