Why the study?
Assessment of coronary microvascular dysfunction remains limited in routine clinical practice despite its clinical implications, prompting interest in alternative angiography-derived indices in the catheterisation laboratory.
Do IMR hybrid and IMR angio accurately predict coronary microvascular dysfunction compared to bolus thermodilution-based IMR in patients with coronary artery disease?
Do IMR hybrid and IMR angio accurately predict coronary microvascular dysfunction compared to bolus thermodilution-based IMR in patients with coronary artery disease?
Both hybrid and fully angiography-derived indices of microcirculatory resistance are viable and accurate alternatives to conventional bolus thermodilution for assessing coronary microvascular dysfunction.
Both IMR hybrid and angio show comparable accuracy; leaves open prospective outcome validation before clinical adoption.
Background Despite growing evidence of its clinical implications, assessment of coronary microvascular dysfunction (CMD) remains limited in routine clinical practice. Hence, there is an increasing interest in angiography‐derived indices to encourage assessment of CMD in the cardiac catheterisation laboratory. Aims We investigate here an alternative approach, using a combination of pressure‐wire‐based assessment of distal coronary pressure (P d ) and an angiography‐derived surrogate of coronary flow, to derive a hybrid index of microcirculatory resistance (IMR hybrid ). Methods Patients enroled prospectively under the Oxford Acute Myocardial Infarction (OxAMI) study were included in the OxAMI HYBRID substudy. The accuracy of IMR hybrid was assessed in diagnosing CMD using bolus thermodilution‐based Index of Microcirculatory Resistance (IMR) as a reference. The accuracy of IMR hybrid was then compared against a fully angiography‐derived index of microvascular resistance (IMR angio ). Results One hundred and eighty six patients were enroled, of which 121 with acute coronary syndrome and 65 with stable coronary artery disease. A total of 240 vessel analyses were performed. Both IMR hybrid and IMR angio correlated with IMR (rho = 0.71, p < 0.001 and rho = 0.71, p < 0.001 respectively) and showed good and comparable overall diagnostic accuracy in predicting IMR ≥ 25 (80.8% and 83.1% respectively) with a receiver operator curve (ROC) analyses showing similar AUC of 0.86 (95% CI 0.82–0.91, p < 0.001) for IMR hybrid and 0.86 (95% CI 0.809–0.906, p < 0.001) for IMR angio , p for comparison = 0.641. Conclusion Both approaches, IMR hybrid and IMR angio are viable and comparable indices correlating with bolus thermodilution‐based IMR and retaining good diagnostic accuracy. IMR hybrid specifically is a simple alternative to conventional bolus thermodilution‐based IMR applicable to any pressure wire system.
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Chai et al. (2024) studied this question.
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