January 1, 2024Open Access
Non-invasive pressure–volume loops using the elastance model and CMR: a porcine validation at transient pre-loads
Structured PICO
Does a non-invasive elastance model using CMR accurately estimate pressure-volume loops and haemodynamic parameters compared to invasive measurements in a porcine model at transient pre-loads?
P
Population
15 pigs (n = 7 naïve, n = 8 with ischaemic cardiomyopathy)
I
Intervention
Non-invasive elastance model-based estimation of pressure-volume (PV) loops using real-time left ventricular volumes from cardiovascular magnetic resonance (CMR)
C
Comparator
Simultaneous measurements of invasive pressure and volume from real-time CMR acquired concurrent to an inferior vena cava (IVC) occlusion
O
Outcome
Agreement between model-based and invasive haemodynamic parameters (stroke work, potential energy, ventricular energy efficiency, contractility, and ventriculoarterial coupling) and PV loop dice similarity coefficientsurrogate
A non-invasive elastance model using CMR accurately estimates pressure-volume loops and associated haemodynamic parameters under transient loading conditions in a porcine model.
Abstract
Abstract Aims Pressure–volume (PV) loops have utility in the evaluation of cardiac pathophysiology but require invasive measurements. Recently, a time-varying elastance model to derive PV loops non-invasively was proposed, using left ventricular (LV) volume by cardiovascular magnetic resonance (CMR) and brachial cuff pressure as inputs. Validation was performed using CMR and pressure measurements acquired on the same day, but not simultaneously, and without varying pre-loads. This study validates the non-invasive elastance model used to estimate PV loops at varying pre-loads, compared with simultaneous measurements of invasive pressure and volume from real-time CMR, acquired concurrent to an inferior vena cava (IVC) occlusion. Methods and results We performed dynamic PV loop experiments under CMR guidance in 15 pigs (n = 7 naïve, n = 8 with ischaemic cardiomyopathy). Pre-load was altered by IVC occlusion, while simultaneously acquiring invasive LV pressures and volumes from real-time CMR. Pairing pressure and volume signals yielded invasive PV loops, and model-based PV loops were derived using real-time LV volumes. Haemodynamic parameters derived from invasive and model-based PV loops were compared. Across 15 pigs, 297 PV loops were recorded. Intra-class correlation coefficient (ICC) agreement was excellent between model-based and invasive parameters: stroke work (bias = 0.007 ± 0.03 J, ICC = 0.98), potential energy (bias = 0.02 ± 0.03 J, ICC = 0.99), ventricular energy efficiency (bias = −0.7 ± 2.7%, ICC = 0.98), contractility (bias = 0.04 ± 0.1 mmHg/mL, ICC = 0.97), and ventriculoarterial coupling (bias = 0.07 ± 0.15, ICC = 0.99). All haemodynamic parameters differed between naïve and cardiomyopathy animals (P 0.05). The invasive vs. model-based PV loop dice similarity coefficient was 0.88 ± 0.04. Conclusion An elastance model–based estimation of PV loops and associated haemodynamic parameters provided accurate measurements at transient loading conditions compared with invasive PV loops.