Diagnosis of Myocardial Infarction

WHO criteria for diagnosis of acute myocardial infarction

World Health Organization required at least two of the following criteria:

(1) A history of chest pain

(2) Evolving changes on the ECG

(3) Elevation of serial cardiac markers

Diagnosis of acute myocardial infarction

Either one of the following criteria satisfies the diagnosis for an acute, evolving, or recent MI.

1. Typical rise and gradual fall (cardiac troponin) or more rapid rise and fall (CK-MB) of biochemical markers of myocardial necrosis with at least one of the following:

a.     Ischemic symptoms

b.     Development of pathological Q waves on the ECG.

c.      ECG changes indicative of Ischemia (ST segment elevation of    depression).

d.     Coronary artery intervention (e.g. coronary angioplasty)

2. Pathological findings of an AMI.

International recommendations for use of cardiac biomarkers for detection of myocardial injury and myocardial infarction

• Increase in biomarkers of cardiac injury are indicative of injury to the myocardium, but not of an ischemic mechanism not leading to injury of myocardium.
• Cardiac troponins (I or T) are preferred markers for diagnosis of myocardial injury.
• Increase in cardiac marker proteins reflect irreversible injury.
• AMI is present when there is cardiac damage, as detected by cardiac marker.
• For patients with an ischemic mechanism of injury, prognosis is related to the extent of troponin increases.
• If an ischemic mechanism is unlikely, other causes for cardiac injury should be pursued.
• To rule out MI, samples must be obtained for at least 6 to 9 hours after the symptoms begin.
• After percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG), the significance of marker elevations and patient care should be individualized.