Comparison of a Fully Angiography-Derived Versus a Hybrid of Angiography and Pressure-Wire-Derived Approach to Assess Coronary Microvascular Resistance: The Oxford Acute Myocardial Infarction Hybrid (OxAMI-HYBRID) Study.
Chai J., Marin F., Scarsini R., Kotronias R., Benenati S., Chu M., Couch LS., Langrish J., OxAMI Investigators ., Channon K., Banning A., De Maria GL.
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 (Pd) and an angiography-derived surrogate of coronary flow, to derive a hybrid index of microcirculatory resistance (IMRhybrid). METHODS: Patients enroled prospectively under the Oxford Acute Myocardial Infarction (OxAMI) study were included in the OxAMI HYBRID substudy. The accuracy of IMRhybrid was assessed in diagnosing CMD using bolus thermodilution-based Index of Microcirculatory Resistance (IMR) as a reference. The accuracy of IMRhybrid was then compared against a fully angiography-derived index of microvascular resistance (IMRangio). 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 IMRhybrid and IMRangio 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 IMRhybrid and 0.86 (95% CI 0.809-0.906, p < 0.001) for IMRangio, p for comparison = 0.641. CONCLUSION: Both approaches, IMRhybrid and IMRangio are viable and comparable indices correlating with bolus thermodilution-based IMR and retaining good diagnostic accuracy. IMRhybrid specifically is a simple alternative to conventional bolus thermodilution-based IMR applicable to any pressure wire system.