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Long-term prognosis after myocardial infarction in patients with previous coronary artery bypass surgery
A Wiseman1, D D Waters, A Walling
1Department of Medicine, Montreal Heart Institute, Quebec, Canada.
Insights
Patients with myocardial infarction after bypass surgery had smaller infarcts but more recurrent cardiac events like reinfarction and unstable angina. Previous bypass surgery indicates higher risk for future cardiac events.
Area of Science:
- Cardiology
- Cardiac Surgery
- Clinical Medicine
Background:
- Patients hospitalized with myocardial infarction (MI) after coronary artery bypass grafting (CABG) present unique clinical challenges.
- Comparing outcomes of MI in patients with prior CABG versus those without is crucial for risk stratification.
Purpose of the Study:
- To compare the clinical characteristics, infarct severity, and long-term outcomes of patients experiencing acute myocardial infarction (MI) after coronary artery bypass grafting (CABG) with a control group.
- To determine if prior CABG influences subsequent cardiac events and overall survival post-MI.
Main Methods:
- A cohort of 205 patients with MI post-CABG was compared to 205 control patients with MI.
- Follow-up data were collected for an average of 34 months post-discharge, assessing infarct size, in-hospital mortality, and long-term events including reinfarction, unstable angina, and revascularization procedures.
Main Results:
- Post-CABG patients had significantly smaller infarct sizes (e.g., lower peak serum creatine kinase) compared to controls (p ≤ 0.001).
- In-hospital mortality and 5-year cumulative mortality were similar between groups (p = NS).
- However, the post-CABG group experienced significantly more reinfarctions (40% vs. 23%, p = 0.007), unstable angina admissions (23% vs. 18%, p = 0.04), and revascularization procedures (34% vs. 20%, p = 0.04).
Conclusions:
- Despite smaller infarct size, patients with MI after CABG do not have better survival than other MI patients.
- Previous bypass surgery is a significant predictor of recurrent cardiac events, including reinfarction and unstable angina.
- Patients with prior CABG require vigilant monitoring for adverse cardiac events post-MI.
Abstract:
A group of 205 patients hospitalized with myocardial infarction 2 to 162 months (mean 66) after bypass surgery and 205 control patients with myocardial infarction were compared and followed up for 34 +/- 25 months after hospital discharge. At baseline the postbypass group contained more men (p less than 0.03) and more patients with previous myocardial infarction (p less than 0.06), but the groups were otherwise comparable. Indexes of infarct size were lower in postbypass patients: sum of ST elevation, QRS score, peak serum creatine kinase (CK) (1,115 +/- 994 versus 1,780 +/- 1,647 IU/liter) and peak MB CK (all p less than or equal to 0.001). Postmyocardial infarction ejection fraction was 45 +/- 15% in the postbypass group and 43 +/- 15% in the control group (p = NS); in-hospital mortality rate was 4 and 5%, respectively (p = NS). When patent grafts were taken into account, the two groups were comparable in extent of coronary artery disease. At 5 years after discharge, cumulative mortality was similar in the postbypass and control groups (30 versus 25%, respectively, p = NS). However, postbypass patients had more reinfarctions (40 versus 23%, p = 0.007), more admissions for unstable angina (23 versus 18%, p = 0.04) and more revascularization procedures (34 versus 20%, p = 0.04) than did control patients. The total for these events at 5 years was 70% in the postbypass group and 49% in the control group (p = 0.001). Thus, although patients with previous bypass surgery who develop acute myocardial infarction have a smaller infarct, their subsequent survival is no better than that of other patients with acute myocardial infarction. They experience more reinfarctions and unstable angina. Previous bypass surgery is an important clinical marker for recurrent cardiac events after myocardial infarction.