Diagnosis of MI – Physical Examination and ECG

Physical examination – During the physical examination, the appearance of patients may vary as per the experienced symptoms by them and thus patient may be restless or in severe distress or comfortable. The presence of a cool and pale skin in patients with MI is common and it highlights the vasoconstriction. The blood pressure of the patients may be high or low. The pulse of patients may be irregular and some of them may have low-grade fever (38–39 °C).

In case of a heart failure, doctor can detect the raised hepatojugular reflux and jugular venous pressure. The swelling of the legs because of peripheral edema is also found on inspection. Doctors may also inspect a cardiac bulge with different pace from the pulse rhythm on precordial examination. There could be various abnormalities detected on auscultation including systolic murmurs, paradoxical splitting of the second heart sound, third and fourth heart sound, and pericardial friction rub.

The chief aim of the electrocardiogram is to detect ischemia or acute coronary injury in case of symptomatic and broad emergency department populations. Doctors can use serial ECG for following the rapid changes happening in time. The standard 12 lead ECG does not examine the right ventricle directly, and also does not properly examine lateral and the posterior basal walls of the left ventricle. In fact, acute myocardial infarction may produce a no diagnostic ECG in the distribution of the circumflex artery. The usage of additional ECG leads including the right-sided leads and posterior leads may enhance the sensitivity for posterior and right ventricular myocardial infarction.

Patients can be classified into three groups based on the 12 lead ECG.

1. Patients with ST segment elevation

2. Patients with ST segment depression

3. Patinets with non-diagnostic or normal ECG.

A normal ECG does not mean that the patient do not have acute myocardial infarction. One should not fail to identify the high risk features.

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Diagnosis of Myocardial Infarction

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.

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