Ventricular-arterial coupling during exercise and tilt assessed using a pulse wave velocity-to-global longitudinal strain ratio.

Ventricular-arterial coupling (VAC) is commonly assessed using the echocardiography-derived ratio of arterial elastance to end-systolic elastance (Ea/Ees), a convenient but global construct that collapses ventricular and arterial properties into a single lumped parameter. A proposed index, combining pulse wave velocity and global longitudinal strain (PWV/GLS), provides a mechanistically-grounded representation of coupling by directly integrating measures of arterial stiffness and myocardial deformation. This study compared the ability of Ea/Ees and PWV/GLS to discriminate between acute physiological stress conditions. Twenty healthy young adults (10 females; 23±2 years) completed a randomized crossover graded cycling protocol (25W, 75W, and fixed heart rate ~130 bpm) in supine and 20° head-up tilt (HUT). HUT induced changes in ventricular volume loading, thereby challenging inherent assumptions underlying Ea/Ees. Ea/Ees progressively declined with increasing exercise intensity (main effect of stage p<0.01; all p<0.05 from previous stage), reflecting increased left ventricular elastance (Ees) relative to arterial load (Ea). Ea/Ees showed no detectable differences between supine and HUT either at rest or at any exercise stage (interaction p > 0.05). In contrast, PWV/GLS was less sensitive to exercise intensity (all stages only different from baseline p < 0.05) but showed a difference from supine to HUT at rest (p < 0.01). These findings support a context-dependent approach to VAC assessment: Ea/Ees reflects volumetric-pressure coupling during exercise, whereas PWV/GLS was responsive to fluid shifts and preload changes, supporting its potential as an alternative VAC measure that captures arterial wave propagation and myocardial deformation when the assumption of a negligible V0 is challenged.