Prognostic predictors and outcomes in patients with abnormal myocardial perfusion imaging and angiographically insignificant coronary artery disease

Background: Abnormal stress myocardial perfusion imaging studies (SMPI) with angiographically insignificant coronary artery disease (ICAD) have often been labeled "false positive" scans. We evaluated the prognostic predictors and outcomes in an unselected patient population having abnormal SMPI and ICAD (study group) over a 24 month period of follow-up. Methods: Retrospective study of consecutive patients who had SMPI and subsequent coronary angiography showing ICAD within 6 months of index scan with matched control group with normal scans. Major Adverse Cardiac Events (MACE) were defined as the first occurrence of death or myocardial infarction (MI). Patients were followed up to 24 months from the time of their SMPI to identify the development of MACE. Results: One hundred and twenty five patients formed the study group and one hundred and thirty six patients formed the control group. Over a two-year follow up, approximately 13% of the study group had MACE as compared to 4.2% in the control group (P = .022). Abnormal SMPI, EF < 40% and chronic kidney disease (GFR < 60 ml/min) were independent predictors of MACE in the study group. In multivariate analysis for MACE prediction, chronic kidney disease remained the sole independent predictor regardless of size or severity of perfusion abnormalities (P = <.001). Conclusion: Patients with abnormal SMPI and ICAD have a 13% event rate of MACE over a two-year follow up. CKD seems a very important marker of a higher risk subgroup amongst such patients.