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.

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.