Reference Values for Myocardial Strain by Cardiac Magnetic Resonance Feature Tracking: Insights From Healthy Volunteers and Heart Failure Patients Using Caas MR

Background: Magnetic resonance imaging (MRI) allows for the assessment of myocardial strain and identification of heart failure (HF) patients with reduced (HFrEF), mildly reduced (HFmrEF), or preserved (HFpEF) left ventricular ejection fraction (LVEF). The cardiovascular angiographic analysis system magnetic resonance (Caas MR) strain (Pie Medical Imaging) has recently been implemented in the IntelliSpace Portal Suite (Philips Healthcare) to assess the global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS). However, standard values for this software across different HF entities, as well as normal values, have yet to be established. Thus, this study aimed to establish reference values for the GLS, GCS, and GRS using the Caas MR strain in healthy individuals and HF patients, to assess the ability of these parameters to differentiate between HF subtypes, and to compare CAAS-derived strain values with those obtained using CVI42 software. Methods: Using a 1.5 T Philips Achieva scanner, we analyzed 19 healthy volunteers and 56 HF patients (HFpEF, n = 19; HFmrEF, n = 20; and HFrEF, n = 17) using the feature tracking post-processing software Caas MR Strain. GLS, GCS, and GRS were quantified using 4-chamber-view, 2-chamber-view, and short-axis (SAX) cine images. All volunteers and patients were evaluated by CVI42 to analyze inter-vendor reliability with a validated software. Results: Mean GLS, GCS, and GRS by Caas MR Strain were significantly different for healthy volunteers compared to HF patients (GLS –15.8 ± 1.9% vs. –11.7 ± 3.0%, p < 0.001; GCS –17.0 ± 2.6% vs. –11.4 ± 3.3%, p < 0.001; GRS 27.3 ± 6.2% vs. 14.5 ± 5.5%, p < 0.001). The upper limit of the 99% confidence interval for healthy volunteers was –14.6% for GLS, –15.3% for GCS and the lower limit of the 99% CI for GRS was 23.1%. GLS, GRS, and GCS by Caas MR Strain were significantly different among HF entities (p < 0.001). Intervendor comparison showed very good agreement for GLS and GRS between Caas MR Strain and CVI42 (GLS r = 0.86, p < 0.001; GCS r = 0.83, p < 0.001; GRS r = 0.76, p < 0.001). Conclusion: Magnetic resonance imaging assessment of left ventricular myocardial strain using Caas MR Strain software reliably identifies HF patients. Discrimination between the different HF entities is potentially feasible by GLS, GCS, and GRS. Intervendor agreement was most robust for GLS and GCS, but less robust for GRS. For practical clinical use, we propose cut-off values for GLS above –15%, GCS above –15%, and GRS below 23% to define pathological findings.