Silent myocardial ischemia

Silent myocardial ischemia

Silent myocardial ischemia is detected on electrocardiographic tracings without manifest chest pain. Many a time ECG changes of old myocardial infarction and ischemia are noted on routine ECGs taken for preoperative evaluation or other purposes. According to Framingham study up to one fourth of all myocardial infarctions detected on regular ECG screening could have been clinically silent. Diabetes mellitus with autonomic neuropathy is one important situation in which ischemia may occur without the symptom of chest pain. Another important occasion is the post operative individual on sedation for pain relief.

Total ischemic burden is the sum total of all episodes of silent and manifest ischemic events, usually detected on 24 hour Holter monitoring. An episode of ischemia is ST segment deviation on Holter which lasts at least 1 minute. Total ischemic burden of more than one hour during a day is significant. It may be noted that silent myocardial ischemia is as important as or even more important than manifest ischemia regarding prognosis. It could be dangerous as the individual is not warned by the pain so that he may continue to exert during the episode leading to catastrophic results. Many with silent myocardial infarctions may present later with heart failure due to absence of a diagnosis and early treatment.

Treadmill testing is another situation in which silent myocardial ischemia is documented. Many times, ST deviation is noted on treadmill, requiring termination of test, without manifest symptoms of myocardial ischemia. It is needless to say that coronary angiography and revascularization if feasible needs to be considered in both silent and manifest myocardial ischemia.