An abnormal electrocardiogram indicates heart rhythm abnormalities, damage to the heart muscle or problems with the amount of electrolytes in the blood, notes MedlinePlus. During an ECG, a technician uses electrodes, wires and a machine to measure the electrical activity of the heart.
A normal ECG reading shows a consistent heart rhythm and a heart rate between 60 and 100 beats per minute, states MedlinePlus. Abnormal ECG results are associated with conditions such as heart failure, atrial fibrillation, sick sinus syndrome and multifocal atrial tachycardia. An abnormal reading may also be caused by heart attack, congenital heart defects, inadequate blood supply to the coronary arteries, damage to the heart muscle or inflammation of the heart.
Too much or too little potassium in the blood can cause ECG abnormalities, according to the Cleveland Clinic. Low potassium levels sometimes cause abnormal heart rhythms. An ECG of someone with a high potassium level may show ventricular fibrillation, atrioventricular conduction block or other changes in the heart's rhythm. Too much calcium can also cause abnormal heart rhythms, states Mayo Clinic. An excess of calcium in the blood affects the electrical system of the heart, causing irregular heartbeats.
The ECG is usually performed when a person reports experiencing heart palpitations or chest pain. The test is also used to determine if a patient is healthy enough for surgery or to determine if someone with a family history of heart disease has any heart problems.