Some people have problems with their heart rhythms.
Pacemakers are electronic devices used to help the heart beat more normally.
Heart problems that would normally be detected with ECGs are occasionally missed in patients with pacemakers because the tracing shows only the paced rhythm and not the other heart problems. A heart attack, also known as a myocardial infarction, is caused by blockage of the arteries that supply blood to the heart. Heart attacks are usually detected with an ECG tracing. It is not known, however, whether people who have heart attacks but also have a paced rhythm do worse than people with heart attacks but have no pacemaker and no paced rhythm. To compare treatments and outcomes of heart attacks among people who did or did not have paced rhythms on their initial ECGs.