Increased LV mass linked to discordant stress CMR/ICA results via microvascular resistance

This substudy of the Dan-NICAD 2 trial (NCT03481712) investigated the impact of left ventricular mass (LVM) on discordance between stress cardiac magnetic resonance (CMR) and invasive coronary angiography (ICA) in patients with suspected obstructive coronary artery disease (CAD) identified on coronary computed tomography angiography (CCTA). The study included 354 patients who underwent both rest and stress CMR and ICA for invasive physiological measurements. An abnormal stress CMR was defined as ≥2 contiguous segments with a stress perfusion defect, late gadolinium enhancement, or wall motion abnormality. CMR-derived LVM was sex-adjusted and expressed as a percentage. Haemodynamically obstructive CAD at ICA was defined as visual diameter stenosis >90% or FFR ≤0.80. Results showed LVM was significantly higher in patients with an abnormal stress CMR compared to those with a normal CMR (median difference = 8.0%, P < 0.001). In contrast, LVM was similar between patients with and without haemodynamically obstructive CAD at ICA (median difference = 2%, P = 0.222). When patients were categorized into four binary groups based on normal/abnormal stress CMR and ICA results, both median LVM and the index of microvascular resistance were higher in patients with discordant findings (abnormal stress CMR but normal ICA) compared to patients with concordant normal findings (normal stress CMR and normal ICA). Specifically, median LVM was 124% vs. 111% (P = 0.001), and the index of microvascular resistance was 29 vs. 19 (P = 0.072). The study concludes that in patients with suspected obstructive CAD, increased LVM can confound concordance between stress CMR and ICA, potentially due to increased microvascular resistance, which may decrease the pressure gradient across an epicardial stenosis, resulting in a false high FFR and thus a normal ICA result.