Non-invasive pressure-volume loops from cardiovascular magnetic resonance predict cardiovascular mortality in heart failure with reduced ejection fraction

Abstract Background Heart failure with reduced ejection fraction (HFrEF) is characterized by impaired ventricular energetics secondary to ventricular remodeling. Left ventricular pressure-volume (PV) loop analysis (Figure 1) can now be performed noninvasively using cardiovascular magnetic resonance (CMR) imaging, enabling study of cardiac thermodynamic efficiency without the risk and cost associated with invasive measurements (1–3). Here we investigated whether noninvasive PV loops from CMR can predict cardiovascular death in HFrEF patients. Methods We analyzed 135 datasets (age 60±12 years, 79% male) from HFrEF patients (LVEF≤40%) who underwent clinical CMR examination at our center between 2004-2013. Pressure-volume loop parameters were computed from manually segmented CMR data and same-day brachial blood pressure (Segment 4.0 R11026, Medviso, Lund, Sweden). The primary endpoint was cardiovascular mortality extracted from national registries with a 5-year follow-up. Parameters of interest were selected from univariate Cox regression, and associations with clinical outcome evaluated using multivariate Cox regression. Survival was visualized using Kaplan-Meier analysis. Statistical analysis was performed in R 4.0.3 (R Core Team). Results A total of 19 deaths from cardiovascular causes occurred during follow-up. Univariate Cox regression found stroke work (SW, joule), ventricular efficiency (VE, %), external power (J/s), contractility (mmHg/ml), and energy per ejected volume (mJ/ml) computed from PV loops associated with the primary endpoint alongside age, LVEF, and NT-proBNP level. In multivariate Cox regression adjusted for age, ventricular efficiency remained significant (HR 0.86, p<0.001), while EF did not (p = 0.077). Event-free survival is shown in Figure 2. Conclusion Ventricular efficiency derived from non-invasive pressure-volume loop analysis from standard CMR scans, may outperform LV EF as a predictor of cardiovascular mortality in HFrEF. Figures: Figure 1. Example of left ventricular pressure-volume (PV) loop. The area enclosed by the loop is the stroke work (SW). The area bounded by the PV loop and the end-systolic pressure-volume relationship (ESPVR) is the potential energy (PE). Ventricular efficiency (VE) is calculated as SW/(PE+SW). Figure 2. Kaplan-Meier plots of survival by tertiles of stroke work and ventricular efficiency.Figure 1Figure 2