Coronary volume-to-left ventricular mass ratio as a predictor of agreement between myocardial perfusion- and invasive fractional flow reserve measurements

Background Patients with coronary artery disease (CAD) often experience chest pain caused by myocardial ischemia, arising from a mismatch between coronary blood oxygen supply and myocardial oxygen demand. Myocardial perfusion imaging and invasive coronary angiography fractional flow reserve (ICA-FFR) are established modalities for the diagnostic evaluation of patients with suspected obstructive CAD. However, discordance between FFR and the extent of myocardial perfusion defects is frequently observed in moderate stenosis. The coronary volume-to-left ventricular mass ratio (V/M-ratio) has been suggested to describe this relation in supply-demand imbalance. However, it remains unknown whether the V/M-ratio can predict agreement between stress cardiac magnetic resonance (CMR) and ICA-FFR. Purpose To investigate the impact of V/M-ratio on the agreement between stress CMR and ICA-FFR measurements in patients with possible myocardial ischemia. Methods This analysis was based on a prospective, multi-center study of 4407 patients referred for cardiac computed tomography angiography (CCTA) due to symptoms suggestive of obstructive CAD. In total 461 patients with suspected stenosis at CCTA underwent CMR and ICA. ICA-FFR was performed in 205 patients with 30-90% diameter stenosis. Patients with severe stenosis (>90%), did not undergo ICA-FFR and were excluded from the analysis. Abnormal CMR were defined as clinically relevant subendocardial or transmural signal changes during stress imaging or irreversible defects in ≥ 2 continuous segments by late gadolinium enhancement imaging. An abnormal ICA-FFR was defined as ≤0.80. Results In the analysis, 205 patients (mean age 63 years, 69% male) were included. The mean total coronary volume was 2911mm3 (sd:875), mean left ventricle mass was 141g (sd:40) and the mean V/M-ratio 21.2 mm3/g (sd:5.8). CMR perfusion test had 36 (18%) diagnosed with abnormal perfusion and ICA-FFR had 73 (36%) with abnormal flow measurements. V/M-ratio evaluated as a predictor of abnormal ICA-FFR or abnormal CMR perfusion using multivariable adjusted logistic regression models showed OR: 0.90 ([0.85:0.96], p<0.01) and OR: 0.91 ([0.84:0.98], p<0.02) respectively, per 1mm3/g increase in V/M-ratio (Figure 1). The V/M-ratio’s impact on concordance between CMR and ICA-FFR result based on CMR normal (p=0.049) or abnormal (p=0.071) perfusion is shown in figure 2. Conclusions In this study, V/M-ratio was shown as an independent predictor of both abnormal CMR and abnormal ICA-FFR results when adjusted for established clinical covariates. Furthermore, V/M-ratio impacted the discordance between CMR and ICA-FFR results. Our results indicated that the rate of false negative CMR results is higher in patients with low V/M-ratio and the false positive rate is higher in patients with higher V/M-ratios.Figure 1 - log.reg.models of outcomes.Figure 2 - CMR and ICA-FFR agreement