Abstract 18441: Adenosine-Free Functional Assessment of Coronary Stenosis Severity by Contrast-Induced Submaximal Hyperemia

Abstract

Background Detection of clinically significant stenoses by fractional flow reserve (FFR) or hyperemic stenosis resistance (HSR) requires maximal vasodilation, which varies with the amount of adenosine (ADO) given. However, the hemodynamic effect of a coronary artery stenosis is uniquely determined by its quadratic pressure gradient-velocity (ΔP- v ) relationship over a range of physiological flow velocities. Hypothesis Functional stenosis severity can be defined from the ΔP- v relationship in terms of the mean pressure gradient at a fixed submaximal velocity (dP v ). Since contrast medium (CM) induces reactive hyperemia, it provides a convenient means to increase flow for this purpose. Methods In 64 patients, aortic pressure (P a ) and intracoronary pressure (P d ) and v distal to an intermediate stenosis were recorded throughout the response to an i.c. ADO injection (30-60 µg). The curve fit (ΔP=A v +B v 2 ) of each ΔP-v relationship was used to obtain the mean dP v at 20, 25, 30, and 40 cm/s. Ischemic cut-off values for each dP v were defined with respect to FFR (=P d /P a ) <0.75 and HSR (=ΔP/ v ) >0.80 mmHg/cm/s. The dP v with the least discordance was used to assess diagnostic performance. Measurements were repeated after i.c. CM injection (3 ml) in 20 patients. Similarity between ADO and CM-derived ΔP- v relationships was evaluated by comparing the dP v at all fixed velocities. Results ADO-based FFR ranged from 0.27 to 0.97 and HSR from 0.08 to 9.12 mmHg/cm/s. Maximal v after CM was 17 ± 16% lower (p<0.01) and P d was 9 ± 11% higher (p<0.001) compared to ADO. Corresponding ADO and CM ΔP-v relationships showed good agreement; no significant differences were found for dP v at any of the tested velocities. Diagnostic performance was highest for dP v at a velocity of 25 cm/s (dP v25 ), with a cut-off >15.8 mmHg. Sensitivity, specificity, and accuracy compared to FFR were 84%, 92% and 87% for ADO and 88%, 92% and 90% for CM-based dP v25 , respectively. Sensitivity, specificity and accuracy were 100% compared to HSR for both ADO and CM-based dP v25 . Conclusion dP v25 is a promising new index of functional stenosis severity that is based on stenosis hemodynamics and yields a high diagnostic accuracy. This index can be obtained from CM injections and obviates problems associated with the use of adenosine.