The diagnosis of myocardial infarction can be done by using integrating the various methods including the physical examination, history of the presenting illness, electrocardiogram findings and cardiac markers. By using a coronary angiogram, one can visualize the narrowing of arteries and obstructions present on the heart vessels. During the autopsy, a pathologist can diagnose a MI on the basis of anatomopathological findings.
When a patient is arrived in the emergency department, a chest radiograph and routine blood tests are performed to indicate any complications or precipitating causes. The regional wall motion abnormalities on an ECG (echocardiogram) also suggest of a myocardial infarction. A cardiologist may perform Echo in equivocal cases. The Technetium (99mTc) sestamibi or thallium-201 chloride is used in nuclear medicine in stable patients with resolved symptoms for visualizing the areas of reduced blood flow along with pharmocologic stress. The Thallium can also be used for determining if the non-functional myocardium is dead or is in the state of hibernation
Diagnostic criteria of Myocardial Infarction is being formulated by WHO in 1979 and it is followed as a classical criteria to diagnose MI if a patient satisfies two or three of the below mentioned criteria.
1. The clinical history of chest pain (ischaemic type) lasts for over 20 minutes
2. Serial ECG tracings shows changes
3. Levels of Serum cardiac biomarkers like troponin and creatine kinase-MB fraction rise and fall
The WHO criteria were modified in 2000 for giving more importance to cardiac biomarkers. As per the new refined guidelines, if a cardiac troponin rise is accompanied by pathological Q waves, coronary intervention,typical symptoms, ST elevation or depression then it is diagnostic of MI.
The early diagnosis goes a long way in preventing the MI in patients by providing them the effective treatment therapies.