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Diagnostic and Prognostic Performance of Microvascular Resistance Reserve
Quick Takes
- The current study evaluated the diagnostic and prognostic performance of microvascular resistance reserve (MRR) to assess coronary vasodilatory capacity in a large group of patients with stable anginal symptoms and across the spectrum of epicardial CAD.
- MRR (optimal cut-off value of 3.0) had good correlation with CFR and similar to CFR, was independently associated with MACE (death, AMI, urgent revascularization) and target vessel failure at 5 years among patients with functionally intermediate or nonsignificant epicardial CAD.
- In addition, MRR was a more reliable indicator of coronary microvascular dysfunction in the presence of functionally significant epicardial disease (FFR <0.75).
Study Questions:
What are the diagnostic and prognostic characteristics of the microvascular resistance reserve (MRR) for the assessment of coronary circulation vasodilatory capacity?
Methods:
A total of 1,481 patients with stable symptoms and a clinical indication for coronary angiography were included from the global ILIAS (Inclusive Invasive Physiological Assessment in Angina Syndromes) registry. MRR was derived as a function of the coronary flow reserve (CFR) divided by the fractional flow reserve (FFR) and corrected for driving pressure. Clinical follow-up was obtained at outpatient clinic visits or by telephone contact to ascertain the occurrence of major adverse cardiac events (MACE) or target vessel failure (TVF). MACE was defined as the composite of all-cause death, acute myocardial infarction (AMI) of the target vessel, and clinically driven (urgent) revascularization through coronary artery bypass surgery (CABG) or percutaneous coronary intervention (PCI). TVF was defined as the composite of cardiac death, AMI of the target vessel, and clinically driven revascularization of the target vessel through CABG or PCI. All patient-reported events were verified by evaluating hospital records or contacting the treating cardiologist or general practitioner.
Results:
The median MRR was 2.97 (Q1–Q3: 2.32–3.86) and the overall relationship between MRR and CFR was good (correlation coefficient [Rs] = 0.88, p < 0.005). The difference between CFR and MRR increased with decreasing FFR (coefficient of determination [R2] = 0.34; coefficient –2.88, 95% confidence interval [CI], –3.05 to −2.73; p < 0.005). MRR was independently associated with MACE at 5-year follow-up (hazard ratio [HR], 0.78; 95% CI, 0.63–0.95; p = 0.024) and with TVF at 5-year follow-up (HR, 0.83; 95% CI, 0.76–0.97; p = 0.047). The optimal cut-off value of MRR was 3.0. Based on this cut-off value, only abnormal MRR was significantly associated with MACE and TVF at 5-year follow-up in vessels with functionally significant epicardial disease (FFR <0.75)
Conclusions:
MRR seems a robust indicator of the microvascular vasodilator reserve capacity. Moreover, in line with its theoretical background, this study suggests a diagnostic advantage of MRR over other indices of vasodilatory capacity in patients with hemodynamically significant epicardial coronary artery disease (CAD).
Perspective:
MRR is a novel index of vasodilator capacity that theoretically is not confounded by the presence of epicardial CAD or use of vasodilators on aortic pressure while measuring microvascular function. The current study evaluated the diagnostic and prognostic performance of MRR to assess coronary vasodilatory capacity in a large group of patients with stable anginal symptoms and across the spectrum of epicardial CAD. MRR (optimal cut-off value of 3.0) had good correlation with CFR and similar to CFR, was independently associated with MACE (death, AMI, urgent revascularization) and TVF at 5 years among patients with functionally intermediate or nonsignificant epicardial CAD. In addition, MRR was a more reliable indicator of coronary microvascular dysfunction in the presence of functionally significant epicardial disease (FFR <0.75). Although there remains a need for prospective assessment of MRR in clinical practice, it potentially could offer prognostic advantage over other indices of microvascular function in the presence of epicardial CAD.
Clinical Topics: Acute Coronary Syndromes, Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Stable Ischemic Heart Disease, Atherosclerotic Disease (CAD/PAD), Aortic Surgery, Cardiac Surgery and SIHD, Interventions and ACS, Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Nuclear Imaging, Chronic Angina
Keywords: Acute Coronary Syndrome, Angina, Stable, Coronary Angiography, Coronary Artery Bypass, Coronary Artery Disease, Fractional Flow Reserve, Myocardial, Microvascular Angina, Myocardial Infarction, Myocardial Ischemia, Myocardial Revascularization, Percutaneous Coronary Intervention, Prognosis, Vasodilator Agents
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