An abnormal EKG can sometimes happen due to a variation in the rhythm of your heart. But it can also be an indicator of a more serious condition, such as a heart attack.

An electrocardiogram (EKG) measures your heart’s electrical activity. This noninvasive test can measure many aspects, from how fast the heart beats to how well its chambers conduct electrical energy.

An abnormal EKG can mean many things. Sometimes an EKG abnormality is a normal variation of a heart’s rhythm, which does not affect your health. Other times, an abnormal EKG can signal a medical emergency, such as a myocardial infarction (heart attack) or a dangerous arrhythmia.

A doctor or medical professional trained in reading EKGs can interpret the readings to determine if you need further treatments. Discover all the causes of an irregular heartbeat.

An EKG machine is typically a portable machine that has 12 leads, or long, flexible, wire-like tubes attached to sticky electrodes. These are placed on designated areas around the heart and on the arms and legs. The electrodes sense the electrical impulses coming from multiple directions. Undergoing an EKG procedure isn’t painful. You don’t have to do anything special to prepare for the test. The test itself typically takes five minutes or less.

The EKG machine doesn’t generate electricity. Instead, it conducts and measures electrical activity.

Typically, the heart conducts electricity in a standard pathway from the right atrium to the left atrium. The electrical current then goes to the atrioventricular (AV) node, which signals the ventricles to contract. The current then flows to an area known as the bundle of His. This area divides into fibers that provide current to the left and right ventricles.

Any disruption in this current can affect the heart’s ability to work well. Ideally, an EKG can measure any potential disruptions.

Because an EKG measures so many different aspects of the heart’s function, abnormal results can signify several issues. These include:

Defects or abnormalities in the heart’s shape and size: An abnormal EKG can signal that one or more aspects of the heart’s walls are larger than another. This can signal that the heart is working harder than normal to pump blood.

Electrolyte imbalances: Electrolytes are electricity-conducting particles in the body that help keep the heart muscle beating in rhythm. Potassium, calcium, and magnesium are electrolytes. If your electrolytes are imbalanced, you may have an abnormal EKG reading.

Heart attack or ischemia: During a heart attack, blood flow in the heart is affected and heart tissue can begin to lose oxygen and die. This tissue will not conduct electricity as well, which can cause an abnormal EKG. Ischemia, or lack of blood flow, may also cause an abnormal EKG.

Heart rate abnormalities: A typical human heart rate is between 60 and 100 beats per minute (bpm). An EKG can determine if the heart is beating too fast or too slow.

Heart rhythm abnormalities: A heart typically beats in a steady rhythm. An EKG can reveal if the heart is beating out of rhythm or sequence.

Medication side effects: Taking certain medications can impact a heart’s rate and rhythm. Sometimes, medications given to improve the heart’s rhythm can have the reverse effect and cause arrhythmias. Examples of medications that affect heart rhythm include beta-blockers, sodium channel blockers, and calcium channel blockers. Learn more about arrhythmia drugs.

Several symptoms can indicate that you may need an EKG to determine if your heart is functioning normally. Seek emergency medical attention if you experience:

Treatment response to an abnormal EKG typically depends on the underlying cause. For example, some people have a very slow heartbeat where the heart doesn’t conduct electrical signals in the correct order. This person may require a pacemaker, which helps restore the heart to a more normal rhythm.

Other people may require medications taken regularly to maintain a more normal heart rhythm.

Someone having a heart attack may require cardiac catheterization or surgery to allow blood flow to return to the heart.

People with electrolyte imbalances may require correction with medications or fluids. For example, a person with dehydration may have imbalanced electrolytes that are causing an abnormal EKG. This person may require fluids, electrolyte-containing beverages, or medications to restore electrolytes.

Sometimes, a doctor may not recommend any treatments for an abnormal EKG. This may be the case if a person doesn’t have troublesome symptoms or if the abnormality is not cause for concern.