Abstract
BACKGROUND: Variations in resting pulsatile coronary flow velocity acceleration/deceleration characteristics (dU/dt) with respect to epicardial lesions and coronary microvascular dysfunction (CMD) remain incompletely understood. METHOD: The coronary dU/dt pattern was extracted from the first derivative of the intracoronary Doppler velocity signal. Univariable and multivariable models evaluated the relationships between the dU/dt amplitudes, epicardial disease as well as CMD, defined by a blunted coronary flow reserve (CFR) adjusted for the concomitant epicardial disease severity (fractional flow reserve, FFR) yielding the microvascular resistance reserve (MRR). Functional CMD was defined by a blunted MRR (≤ 3.0) but normal hyperemic microvascular resistance (hMR < 2.5) whereas structural CMD was defined by a blunted MRR (≤ 3.0) combined with increased hMR (≥ 2.5). Six major acceleration or deceleration peaks were identified in each cardiac cycle; these were a (amplitude of peak diastolic acceleration), b (amplitude of early diastolic deceleration nadir), c (amplitude of peak diastolic re-acceleration), j (amplitude of end-diastolic deceleration nadir), x (amplitude of peak systolic acceleration), and z (amplitude of end-systolic deceleration nadir) waves. RESULTS: Functional CMD was associated with amplification of a (β = 55.944, 95% CI [21.112, 90.777], p = 0.002) and × (β = 44.069, 95% CI [20.182, 67.955], p < 0.001), b (β = -34.019, 95% CI [-50.865, -17.173], p < 0.001), j (β = -48.723, 95% CI [-71.272, -26.174], p < 0.001), and z (β = -31.047, 95% CI [-53.596, -8.498], p = 0.007) waves. Structural CMD was associated with blunted a (β = -76.938, 95% CI [-113.125, -40.751], p < 0.001) and j (β = 24.787, 95% CI [1.361, 48.213], p = 0.039). CONCLUSION: Epicardial disease severity is minimally associated with alterations in the resting dU/dt pattern, whereas CMD endotypes are associated with distinctively altered intrabeat pulsatility characteristics. Stronger acceleration magnitudes at rest do not indicate a healthier microcirculation or absence of CMD. TRIAL REGISTRATION: ClinicalTrials.gov (NCT02328820).