Analysis Of Myocardial Transmural Perfusion Gradient By CMR In Patients With Suspected Coronary Artery Disease

Objective:To evaluate the diagnostic accuracy of transmural gradient perfusion(TPG)and transmural perfusion gradient reserve(TPGR)with 3.0 Tesla Cardiac Magnetic Resonance(CMR)against invasively determined fractional flow reserve(FFR)to detect coronary artery stenosis.Methods:71 patients(57 men,age 60.1 ± 6.4 years)with suspected or known coronary artery disease(CAD)referred for coronary angiography and Fractional flow reserve(FFR)measurement were prospectively recruited and underwent cardiac magnetic resonance(CMR)perfusion imaging prior to invasive coronary studies.Visual analysis of perfusion imaging was completed by 2 experienced observers blinded to all other data.Perfusion imaging was divided into 17 standard segments.The exponential model was used to match the residual function,where we calculated myocardial blood flow(MBF).Myocardial perfusion reserve(MPR)was calculated by dividing the value of the MBF during the stress state by the rest state.We then subdivide each left ventricular(LV)segments into endocardial and epicardial parts equally.Correspond MBF values(MBFendo and MBFepi)were calculated based on previous description.The TPG was defined as the ratio of MBFendo and MBFepi.TPGR was defined as the ratio of TPG in stress and rest sate.The segments were assigned to the respective coronary perfusion territory based on the standardized LV segmentation.X-ray coronary angiography was performed according to the standard methods within 2 weeks after CMR exam.An FFR<0.75 was considered to represent hemodynamic significant coronary artery stenosis.Results:1.39 patients(54.9%)were defined as having CAD,including 27(69.2%)had single-vessel disease,8(20.5%)had 2-vessel disease,and 4(10.3%)had 3-vessel disease.An FFR<0.75 was detected in 32 patients(45.1%)and another 7 patients with severe coronary disease were not suitable for FFR measurement.There were 55 lesion vessels in all.2.MBF and MPR of both endocardium(MBFendo and MPRendo)and transmural myocardium(MBFtrans and MPRtrans)were significantly lower in stenotic territories compared with remote non-stenosis territories(P<0.001).However,in the analysis of epicardium,the MBFepi was not significantly different from stenosis territories and non-stenosis territories(P=0.070).The AUC for stress MBFendo and MPRendo were significantly higher than for stress MBFtrans(0.77 vs.0.71,P<0.01)and MPRtrans(0.83 vs.0.73,P<0.001)respectively on a vessel basis for FFR<0.75.3.A TPG<0.85 predicted significant CAD with sensitivity and specificity of 74.55%and 83.65%,respectively.Sensitivity and specificity of TPGR<0.81 were 90.91%and 89.94%.Area under the receiver-operating curve(AUC)to detect FFR<0.75 was 0.86 for TPG and 0.95 for TPGR.TPGR yielded significantly better sensitivity and specificity for diagnosis of CAD than traditional MBF,MPR and TPG(P<0.0001).Conclusion:1.Endocardium is more vulnerable to ischemia than epicardium.TPG and TPGR analyses with CMR are capable of detecting hemodynamic stenosis of coronary artery and superior to traditional myocardial perfusion analysis.2.TPGR appears to be superior to TPG in the diagnosis of coronary artery stenosis.