AIIMS November 2011 – MCQ 22

Universal definition of myocardial infarction includes all except?
A. Sudden cardiac death
B. New regional wall motion abnormality with raised cardiac biomarkers
C. 3 times rise in troponin levels after coronary artery bypass graft surgery
D. Reinfarction is diagnosed by elevation of troponin levels by 5-7%

Correct answer : C. 3 times rise in troponin levels after coronary artery bypass graft surgery

Given below is the universal definition of myocardial infarction published in ‘Circulation’ – a journal by American Heart Association.
Option A and B are given in the definition.
Option C – 5 times rise in troponin levels after coronary artery bypass graft surgery is considered as CABG related MI instead of 3 times as given in the option. So the statement is wrong and hence not included in the definition.
Option D is correct – ‘Analytical values are considered to be different if they are different by 3 SDs of the variance of the measures. For troponin, this value is 5–7% for most assays at the levels involved with reinfarction.’

Universal Definition of Myocardial Infarction by Kristian Thygesen; Joseph S. Alpert; Harvey D. White; on behalf of the Joint ESC/ACCF/AHA/WHF Task Force for the Redefinition of Myocardial Infarction

Definition of myocardial infarction:

Criteria for acute myocardial infarction
The term myocardial infarction should be used when there is evidence of myocardial necrosis in a clinical setting consistent with myocardial ischaemia. Under these conditions any one of the following criteria meets the diagnosis for myocardial infarction:
Detection of rise and/or fall of cardiac biomarkers (preferably troponin) with at least one value above the 99th percentile of the upper reference limit (URL) together with evidence of myocardial ischaemia with at least one of the following:
— Symptoms of ischaemia;
— ECG changes indicative of new ischaemia [new ST-T changes or new left bundle branch block (LBBB)];
— Development of pathological Q waves in the ECG;
— Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
• Sudden, unexpected cardiac death, involving cardiac arrest, often with symptoms suggestive of myocardial ischaemia, and accompanied by presumably new ST elevation, or new LBBB, and/or evidence of fresh thrombus by coronary angiography and/or at autopsy, but death occurring before blood samples could be obtained, or at a time before the appearance of cardiac biomarkers in the blood
• For percutaneous coronary interventions (PCI) in patients with normal baseline troponin values, elevations of cardiac biomarkers above the 99th percentile URL are indicative of peri-procedural myocardial necrosis. By convention, increases of biomarkers greater than 3 x 99th percentile URL have been designated as defining PCI-related myocardial infarction. A subtype related to a documented stent thrombosis is recognized.
• For coronary artery bypass grafting (CABG) in patients with normal baseline troponin values, elevations of cardiac biomarkers above the 99th percentile URL are indicative of peri-procedural myocardial necrosis. By convention, increases of biomarkers greater than 5 x 99th percentile URL plus either new pathological Q waves or new LBBB, or angiographically documented new graft or native coronary artery occlusion, or imaging evidence of new loss of viable myocardium have been designated as defining CABG-related myocardial infarction
• Pathological Endings of an acute myocardial infarction.

Criteria for prior myocardial infarction
Any one of the following criteria meets the diagnosis for prior myocardial infarction:
• Development of new pathological Q waves with or without symptoms
• Imaging evidence of a region of loss of viable myocardium that is thinned and fails to contract, in the absence of a non-ischaemic cause
• Pathological Endings ofa healed or healing myocardial infarction

Ref: circ.ahajournals.org/content/116/22/2634.full.pdf

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AIIMS November 2011 – MCQ 21

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