Diagnostic performance and prognostic impact of coronary angiography‐based Index of Microcirculatory Resistance assessment: A systematic review and meta‐analysis

Abstract Background The Index of Microcirculatory Resistance (IMR), measured with a pressure‐thermistor tipped coronary guidewire has been established as a gold standard for coronary microvascular assessment. Angiography‐based IMR (angio‐IMR) is a novel method to derive IMR without intracoronary instrumentation or the need for adenosine. Methods PubMed and Embase databases were systemically searched in November 2021 for studies that measured angio‐IMR. The primary outcomes were pooled sensitivity and specificity as well as the area under the curve (AUC) of the summary receiver operating characteristic curve using IMR as a reference standard. Results A total of 129 records were initially identified and 8 studies were included in the final analysis. Overall, 1653 lesions were included in this study, of which 733 were in patients presenting with ST‐segment elevation myocardial infarction. Angio‐IMR yielded high diagnostic performance predicting wire‐based IMR with pooled sensitivity = 0.81 (95% confidence interval: 0.76, 0.85), specificity = 0.80 (0.72, 0.86), and AUC = 0.86 (0.82, 0.88), which was similar irrespective of patient presentation. When the clinical outcome was compared between high versus low angio‐IMR in patients presenting with myocardial infarction, high angio‐IMR predicted an increased risk of major adverse cardiac events (MACE). Conclusion Our study found that coronary angio‐IMR has relatively high diagnostic performance as well as prognostic values predicting MACE, supporting its use in clinical practice.