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Ischemia Change in Stable Coronary Artery Disease Is an Independent Predictor of Death and Myocardial Infarction
Study Questions:
What is the independent prognostic significance of ischemia change in stable coronary artery disease (CAD)?
Methods:
From the Duke Cardiovascular Disease and Nuclear Cardiology Databanks, 1,425 consecutive patients with angiographically documented CAD who underwent two serial myocardial perfusion single-photon emission computed tomography scans were identified. Ischemia change was calculated for patients undergoing medical therapy alone, percutaneous coronary intervention, or coronary artery bypass grafting. Patients were followed for a median of 5.8 years after the second myocardial perfusion scan. Cox proportional hazards regression modeling was used to identify factors independently associated with the primary outcome of death or myocardial infarction (MI). Formal risk reclassification analyses were conducted to assess whether the addition of ischemia change to traditional predictors resulted in improved risk classification for death or MI.
Results:
More medical therapy patients (15.6%) developed ≥5% ischemia worsening compared with those undergoing percutaneous coronary intervention (6.2%) or coronary artery bypass grafting (6.7%) (p < 0.001). After adjustment for established predictors, ≥5% ischemia worsening remained a significant independent predictor of death or MI (hazard ratio, 1.634; p = 0.0019) irrespective of treatment arm. Inclusion of ≥5% ischemia worsening in this model resulted in significant improvement in risk classification (net reclassification improvement 4.6%, p = 0.0056) and model discrimination (integrated discrimination improvement 0.0062, p = 0.0057).
Conclusions:
The authors concluded that in stable CAD, ischemia worsening is an independent predictor of death or MI, resulting in significantly improved risk reclassification when added to previously known predictors.
Perspective:
This study reports that ≥5% worsening ischemia was a strong, independent predictor of death or MI after adjustment for established predictors and irrespective of treatment arm. Also, the addition of ≥5% worsening ischemia to traditional predictors resulted in significant improvement in the classification of risk for prediction of death or MI. If patients have had two consecutive myocardial perfusion single-photon emission computed tomography (MPS) studies performed for appropriate clinical reasons, the information regarding ischemia change may be used to improve prognostication in these patients. However, these study data should not be used as justification for performing serial MPS scans. Randomized prospective trials are required before any such recommendations can be proposed.
Keywords: Incidence, Coronary Artery Disease, Myocardial Infarction, Myocardial Ischemia, Tomography, Cardiology, Risk Factors, Coronary Artery Bypass, Percutaneous Coronary Intervention
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