Perioperative Myocardial Injury

Question 1

Cardiomyocyte Contractile Apparatus

Answer 1

• Troponin C: Binds to Calcium
• Troponin T: Connects troponin complex to tropomyosin allowing actin-myosin binding
• Troponin I: Inhibits ATP activity when bound to actin

Question 2

Myocardial Injury after Non-cardiac Surgery (MINS)

Answer 2

VISION- Trop T >20 within 72hrs of surgery, with no evidence of a non-ischaemic cause for raised trop T (eg. fast AF, PE, sepsis)
AHA- Trop T or I above the 99th percentile of the upper reference limit within 30 days of surgery with absence of an overt non-ischaemic cause

Question 3

Acute Myocardial Infarction Definition (4th Universal Defnintion)

Answer 3

Trop >99th upper reference limit + evidence of ischaemia with >1 of the following: symptoms of MI, new ischaemic ECG changes, development of pathological Q waves on ECG, ECHO evidence of new RWMAs, identification of coronary thrombus (angio or autopsy)

Type One: secondary to atherothrombotic coronary artery disease, usually precipitated by plaque disruption
Type Two: secondary to mismatch of O2 supply and demand of the myocardium (70% of intra-op MIs)
Type Three: sudden cardiac death assoc with symptoms or signs of MI

Question 4

Incidence of MINS

Answer 4

VISION 8% in >45yrs undergoing non-cardiac surgery

Question 5

Risk Factors for MINS

Answer 5

• Age
• Male
• Known Coronary Artery Disease
• HTN
• Prev MI
• Heart failure
• CKD
• Emergency Surgery
• General surgery

Question 6

Prevention of perioperative myocardial injury

Answer 6

• Lifestyle changes: lose weight, stop smoking, reduce ETOH
• Optimisation of cardiac risk factors
• Avoid hypotension (esp sys <90), anaemia, hypoxia and tachycardia intra-op
• Possibly statins