Pressure-derived estimations of coronary flow reserve are inferior to flow-derived coronary flow reserve as diagnostic and risk stratification tools

Abstract

Background: Pressure-derived coronary flow reserve (CFR_pres) and pressure-bounded CFR (CFR_pb) enable simple estimation of CFR from routine pressure measurements, but have been inadequately validated. We sought to compare CFR_pres and CFR_pb against flow-derived CFR (CFR_flow) in terms of diagnostic accuracy, as well as regarding their comparative prognostic relevance.

Methods: We evaluated 453 intermediate coronary lesions with intracoronary pressure and flow measurements. CFR was defined as hyperemic flow/baseline flow. The lower bound (CFR_pres) and upper bound of CFR_pb were defined as √[(ΔP_hyperemia) / (ΔP_rest)] and [(ΔP_hyperemia) / (ΔP_rest)], respectively. Long-term follow-up (median: 11.8-years) was performed in 153 lesions deferred from treatment to document the occurrence of major adverse cardiac events (MACE) defined as a composite of cardiac death, myocardial infarction and target vessel revascularization. CFR < 2.0 was considered abnormal.

Results: CFR_pb was normal or abnormal in 56.7% of stenoses, and indeterminate in 43.3% of stenoses. There was a poor diagnostic agreement between CFR_pres and CFR_pb with CFR_flow (overall agreement: 45.5% and 71.6% of vessels, respectively). There was equivalent risk for long-term MACE for lesions with abnormal versus normal CFR_pres (Breslow p = 0.562), whereas vessels with abnormal CFR_flow were significantly associated with increased long-term MACE (Breslow p < 0.001). For vessels where CFR_pb was abnormal or normal, there was equivalent risk for long-term MACE for vessels with abnormal versus normal CFR_pb (Breslow p = 0.194), whereas vessels with abnormal CFR_flow were associated with increased MACE rates over time (Breslow p < 0.001).

Conclusions: Pressure-derived estimations of CFR poorly agree with flow-derived measurements of CFR, which may explain the inferior association with long-term MACE as compared to flow-derived CFR.

Keywords: Coronary flow reserve; Long-term clinical outcome; Pressure-bounded coronary flow reserve; Pressure-derived coronary flow reserve.