Introduction:
Although coronary flow reserve (CFR) has been the only physiological way to evaluate the coronary microvascular (MV) function until recently, hyperemic MV resistance (hMR) have been developed as a newer modality measuring directly coronary MV function. Discordance between CFR and hMR may reflect various coronary hemodynamic situations.
Hypothesis:
Simultaneous measurement of CFR/hMR in pts without coronary obstruction could provide us deeper appreciation of hemodynamic functional alterations in coronary microvasculature.
Methods:
In 44 pts without coronary stenosis (diameter stenosis >50%), CFR and hMR were measured utilizing a dual sensor (Doppler velocity and pressure)-equipped guidewire. To evaluate coronary MV hemodynamics, pts were categorized into four CFR/hMR quadrants using a cutoff values of CFR≥2.0 and hMR<1.7 (median value of all study subjects) (Figure).
Results:
Discordance results between CFR/hMR was present in 39% of patients (17 of 44), with CFR≥2.0 and hMR≥1.7 in 30% (13 of 44) and CFR<2.0 and hMR<1.7 in 9% (4 of 44). There were significantly negative correlation between hMR and
hyperemic
average peak velocity (APV) (r=-0.73, p<0.0001), CFR and
baseline
APV (r=-0.66, p<0.001) despite no correlation between CFR and hyperemic APV (r=0.25, p=0.1). Baseline APV and hyperemic APV were significantly different among these groups (baseline APV; group 2 vs. group 3, 12.0±5.7 vs. 30.5±7.2, p=0.02, group 2 vs. group 4, 12.0±5.7 vs. 21.3±8.5, p=0.002, hyperemic APV; group 1 vs. group 4; 51.2±10.4 vs. 28.7±10.2, p<0.0001, group 1 vs. group 2, 51.2±10.4 vs. 32.5±13.6, p=0.03). Four CFR/hMR quadrants thus represent 4 different types of coronary blood flow-perfusion pressure relationship (Figure).
Conclusions:
In pts without coronary obstruction, CFR was related to coronary autoregulation state and hMR to hyperemic state. Simultaneous CFR/hMR measurement might provide new physiological insight about coronary MV hemodynamics.
Coronary obstruction: a rare but devastating complication during transcatheter aortic valve-in-valve implantation