Silent Myocardial Ischemia

Silent myocardial ischaemia is objective evidence of ischaemia (ECG, perfusion or wall motion changes) without angina. It accounts for most ischaemic episodes recorded during ambulatory monitoring.

Cohn classification

• Type I: asymptomatic with no prior infarction or angina.
• Type II: silent ischaemia after infarction.
• Type III: silent episodes in patients who also have angina.
• Prevalence is 2 to 10% in middle aged asymptomatic adults, higher in diabetics (up to 20 to 25%).
• Causes of reduced pain perception: autonomic neuropathy, higher pain threshold, elevated endorphins, age and diabetes.
• Prognosis is similar to symptomatic ischaemia when burden is equal. It predicts infarction and death.

• No symptoms, or atypical equivalents (fatigue, dyspnoea, nausea).
• Detected through screening of high risk individuals, preoperative evaluation, incidental ECG changes or sudden complications (infarction, heart failure, arrhythmia).
• Diabetics with neuropathy may present with arrhythmia or heart failure as the first sign.

• Resting ECG for Q waves and ST T changes.
• Exercise ECG or stress imaging in high risk groups (diabetes with other risk factors, peripheral arterial disease, strong family history, long standing hypertension).
• Ambulatory ECG shows ST depression of 1 mm or more lasting 1 minute, separated by 1 minute from other episodes. Episodes cluster in the morning and at lower heart rates than angina.
• Coronary CT angiography or calcium scoring for risk stratification.
• Invasive angiography for high risk findings (extensive ischaemia, reduced ejection fraction, exercise hypotension).
• Routine screening of asymptomatic low risk adults is not recommended.

• Treat as chronic coronary disease.
  • Aspirin 75 to 100 mg daily, high intensity statin, ACE inhibitor.
  • Beta blocker (bisoprolol 2.5 to 10 mg) as first antiischaemic agent, with amlodipine or diltiazem as alternatives.
  • Targets: LDL cholesterol below 55 mg/dL, blood pressure below 130/80 mmHg, HbA1c about 7%.
• Revascularisation follows the same indications as symptomatic disease (left main, multivessel disease with diabetes, large ischaemic territory, reduced ejection fraction).
• Diabetics: add SGLT2 inhibitor (empagliflozin 10 mg) or GLP 1 agonist (semaglutide up to 1 mg weekly) for cardiovascular benefit.
• Lifestyle: smoking cessation, supervised exercise, weight loss.
• Follow up with symptom review and periodic functional testing when clinical status changes. Re testing intervals of 2 to 3 years are reasonable after a negative test in high risk diabetics.