1. Overview & Epidemiology
Diabetes is one of the top risk factors for myocardial infarction (MI). The relationship between diabetes and Acute Coronary Syndromes (ACS) is critical for CDEs to understand.
- Prevalence: Approximately 30–50% of people admitted with ACS have either known diabetes or previously undiagnosed diabetes (or prediabetes).
- Worse Outcomes: Compared to those without diabetes, people with diabetes have:
- 3-fold increased risk of ACS.
- Events occur 15 years earlier.
- 2-fold increased mortality (short and long-term).
- Care Gap: People with diabetes are historically less likely to receive guideline-recommended therapies (like early invasive strategies) despite having greater benefit from them.
2. Screening for Diabetes in ACS
Because stress hyperglycemia is common and undiagnosed diabetes is prevalent, specific screening protocols are recommended upon admission for ACS.
The Screening Algorithm:
- Measure: Admission A1C and Random Plasma Glucose (PG) in all ACS patients without a history of diabetes.
- Interpret:
- A1C 6.5% OR Random PG 11.1 mmol/L: Presumed diabetes/stress hyperglycemia. Action: Start in-hospital capillary blood glucose monitoring (AC and HS for 48 hours).
- A1C 5.5 – 6.4%: “At Risk.” Action: Rescreen after discharge .
- A1C < 5.5%: Normal.
3. In-Hospital Glycemic Management
Hyperglycemia in the first 24–48 hours post-ACS is associated with increased mortality.
- Target: If random BG is mmol/L, treat to maintain BG between 7.0 – 10.0 mmol/L.
- Method: Insulin therapy is often required. The goal is to avoid both severe hyperglycemia and hypoglycemia (which can negate benefits).
- Note: The guidelines do not recommend “tight” control (e.g., normal range) in the acute phase as evidence remains inconclusive and hypoglycemia risk is high.
4. Pharmacotherapy: Antiplatelet Agents
Platelets in people with diabetes are “hyperactive” and pro-thrombotic. Therefore, potent antiplatelet therapy is crucial.
A. ASA (Aspirin):
- Standard of care for all ACS patients.
B. P2Y12 Inhibitors (The Second Antiplatelet):
- Clopidogrel: A weaker inhibitor; many patients with diabetes have high residual platelet activity on Clopidogrel.
- Ticagrelor (Brilinta) & Prasugrel (Effient): Preferred over Clopidogrel.
- TRITON-TIMI 38 (Prasugrel): Showed a 30% reduction in primary endpoints (CV death, MI, stroke) in patients with diabetes compared to Clopidogrel.
- PLATO (Ticagrelor): Significant reduction in CV death and MI compared to Clopidogrel.
- Long-Term Therapy: For high-risk patients (history of MI + diabetes), extending Ticagrelor (60 mg BID) up to 3 years reduced CV death, MI, or stroke (PEGASUS-TIMI 54 trial).
5. Revascularization Strategies
How to fix the blocked arteries?
- NSTE-ACS (Non-ST Elevation): An early invasive strategy (angiogram/intervention) is preferred over a conservative (“wait and see”) approach for people with diabetes.
- CABG vs. PCI: For complex multi-vessel disease, Coronary Artery Bypass Grafting (CABG) is preferred over PCI (stenting) because it reduces death and MI in this specific population.
- STEMI (ST Elevation):
- Primary PCI: Preferred if available.
- Fibrinolysis (Clot busters): If PCI is not available. Important Exam Note: Diabetic Retinopathy is NOT a contraindication to fibrinolysis (ocular hemorrhage is extremely rare).
6. 2018 Diabetes Canada Clinical Practice Guidelines Recommendations
Key takeaways from the “Recommendations” section (Page S192).
Screening: In all people with ACS without known diabetes, measure A1C and Random PG. If A1C 6.5% or Random PG 11.1, initiate in-hospital monitoring [Grade D, Consensus].
Glycemic Targets: If BG > 11.0 mmol/L, treat to target 7.0–10.0 mmol/L [Grade C, Level 2].
Antiplatelet Choice: In patients with diabetes and ACS undergoing PCI, use Prasugrel [Grade A] or Ticagrelor [Grade B] rather than clopidogrel.
Extended Therapy: Consider prolonged Ticagrelor (60 mg BID) for up to 3 years in high-risk patients [Grade B, Level 2].
Revascularization: For complex coronary anatomy (multi-vessel), CABG should be considered rather than complex PCI [Grade A, Level 1].
Fibrinolysis: Retinopathy should not be a contraindication to fibrinolysis [Grade B, Level 2].