Abstract 2831: Endomyocardial-to-Epimyocardial Blood Flow Ratio Distinguishes Severity of Coronary Artery Disease: A Perfusion CMR Study
Background: Ischemia propagates as a wave front from the endocardial (ENDO) to the epicardial (EPI) surface. Normally, myocardial blood flow (MBF) is higher in the ENDO than EPI. We hypothesized that the ENDO/EPI ratio could differentiate the severity of coronary stenoses in a clinical patient population.
Methods: Perfusion CMR was performed in 29 patients within 30 days of x-ray angiography and quantitative coronary analysis. During adenosine infusion and at rest, dual boluses of Gd-DTPA were infused (4ml/s) to quantify arterial input function (0.0075mM/kg) and tissue perfusion (0.075mM/kg) in 3 short axis slices using hybrid gradient echo/echo planar imaging. ENDO and EPI MBF for rest and stress were estimated by determining the peak amplitude of the impulse response derived from Fermi function deconvolution. Stress and rest ENDO/EPI ratios were calculated and then corrected (corr) for rate-pressure product (RPP) using the formula ENDO/EPI * (SBP*HR*10−4).
Results: Coronary stenosis (CS) >50% was present in 23 of 29 patients. Hypertension, diabetes, and dyslipidemia were present in 23, 9, and 26 patients, respectively. Stress corrENDO/EPI (mean±SE) was inversely related to CS (CS<50% = 1.356 ± 0.030, CS 50–70% = 1.266 ± 0.029, and CS>70% = 1.149 ± 0.039; p<0.05) (Figure⇓). The relationship persisted after exclusion of the 56 segments with a myocardial scar (p<0.05). No relationship existed between CS and rest ENDO/EPI, rest corrENDO/EPI, or uncorrected stress ENDO/EPI.
Conclusions: Stress corrENDO/EPI is inversely related to the severity of CS. Quantitative stress endo/epi ratios can distinguish intermediate from severe stenoses in patients with known or suspected CS.