What is a silent myocardial infarction? Cardiology Basics

What is a silent myocardial infarction? Cardiology Basics

Silent myocardial infarction is one in which the person does not know that myocardial infarction has occurred. This can be because chest pain was not felt or was only mild. It can also be missed if the person was under sedation or under general anaesthesia when it occurred. In earlier community studies like the Framingham Heart Study, in which ECG was recorded every two years, it was shown that up to one fourth of the previous myocardial infarctions detected on ECG were silent.

Silent myocardial infarctions are more likely in those with diabetes mellitus. Long standing diabetes affects the nerves of the heart so that they may not feel the chest pain which is common with a myocardial infarction. Sometimes they come later with breathlessness which occurs when there is heart failure as a consequence of undetected and untreated myocardial infarction.

Though ECG studies showed one fourth as silent myocardial infarction, studies of high risk patients undergoing surgery under anaesthesia have shown that even half of the myocardial infarctions in this situation can be silent. The detection rate of myocardial infarction in this setting is higher because along with ECG, troponin estimation is also done to detect even smaller infarcts which may be missed by an ECG. Another reason is that they are frequently given medications for pain which may cause the myocardial infarction to be silent.

Silent myocardial infarction is a disadvantage than an advantage though one does not have to suffer pain. Pain is a warning symptom which allows to take care and medical attention. Those who do not recognize the myocardial infarction due to lack of pain will not take rest or get medical attention and thereby miss secondary preventive measures. So, the outcome may even be worse than a symptomatic myocardial infarction.

They often present later with heart failure due to reduced left ventricular ejection fraction. Few of the lucky ones do not have any symptoms or worsening and they are incidentally detected later during some screening program or routine medical check-up. Once detected, they also need secondary preventive measures like a symptomatic myocardial infarction.