Despite the advent of expensive and sophisticated cardio-logic tests, the electrocardiogram remains the most reliable tool for the confirmation of acute myocardial infarction. The electrocardiogram — not the cardiac enzymes, tropo-nins, CK–MB, echocardiogram, or Sector PET scan — dictates the rapid administration of lifesaving thrombolytic therapy. There is no test to rival the electrocardiogram in the diagnosis of arrhythmia, which is a common problem seen in clinical practice. Also, the diagnosis of acute pericarditis can only be confirmed by electrocardiographic findings. The very common condition of myocardial ischemia which causes chest pain in patients with angina can be confirmed in some by electrocardiographic findings at rest and particularly during exercise.