Perioperative Medicine - Cardiac

Mechanism of Peri-operative MI:

• Plaque fissuring due to Inflammatory state and stress
• Hypercoagulability precipitating acute coronary thrombosis.
• Hypoxic state secondary to anaesthesia, hypothermia, bleeding and anaemia.

Peri-operative cardiac risk can be assessed by many different methods:

Eagle Criteria

1. Age more than 70 yrs.
2. DM - requiring therapy other than diet
3. CCF
4. MI - q wave on ECG
5. History of angina

2 Risk factors - < 5% risk
3 or more risk factors - 30 - 40 % risk

Revised Cardiac Risk Index ( Lee et al )

1. High risk surgery - AAA repair, thoracic and abdominal
2. IHD - AMI, Q wave, angina, nitrates, EST positive
3. CCF
4. CVA - stroke, TIA
5. Pre-op insulin
6. Serum creatinine > 180 micromol/L

3 risk factors - intermediate
4 or more risk factors - high risk

High Risk patient can be further assessed by doing Dobutamine Stress Echocardiogram.

• If ECG changes at high work load - 20 % risk
• If ECG changes at low work load - 70 % risk

Management,

Cardiac Prophylactic measures include:

• Coronary revascularisation ( PCI or CABG )

• Adjuvant therapies - Beta blockers & Aspirin

• No high quality evidence of decreased perioperative cardiac risk according to: other anti-anginal medications and type of surgery - open vs laproscopic
  

Coronary revascularisation ( PCI or CABG )

The underlying mechanism of perioperative cardiac event is different from usual cardiac event as described before. The decision for revascularisation should rest on proven indications in non-operative setting - for symtomatic control or for prognosis.

Indications in which PCI is beneficial for prognosis include:

1. Left main coronary lesion
2. Proximal LAD lesion
3. Triple vessel disease
4. Ejection Fraction less than 40 %

If PCI is done, surgery should be deferred for 6 weeks or longer. ( within 6 weeks - 20 % mortality, 18 % non-fatal MI and 28 % major bleeding )