Non-invasive pressure–volume loop analysis in left ventricular load manipulation

Background: Clinical monitoring of patients with heart failure or cardiomyopathy is facilitated by detailed assessment of cardiac loading conditions. Specifically, alterations in preload and afterload may unmask pathology through effects on ventricular pressure–volume (PV) relations. Therefore, the aim was to assess non-invasive PV loops during left ventricular load manipulation in healthy participants and in patients with hypertrophic cardiomyopathy (HCM). Methods: In total, n = 46 participants were studied in paired experiments at baseline and during load manipulation. Controls (n = 24) and patients with HCM (n = 14) were assessed at baseline and during intravenous infusion of 1.5–2 L isotonic saline, and another group of volunteers (n = 8) was assessed at baseline and during infusion of glyceryl trinitrate (GTN). Non-invasive PV loops were calculated from cardiovascular magnetic resonance (CMR) and concurrent brachial blood-pressure measurements. Results: Saline infusion brought about increased end-diastolic and decreased end-systolic volumes in controls, but not in HCM. Concurrently, PV loops revealed mechanistic differences, where controls but not HCM exhibited decreased arterial elastance and potential energy during load manipulation. In both groups, ventricular-arterial coupling (VAC) decreased, and ventricular efficiency and cardiac output increased. Infusion of GTN resulted in decreased ventricular volumes. Contrary to saline infusion, volunteers receiving GTN retained unchanged arterial elastance, VAC, ventricular efficiency and cardiac output. Conclusion: Non-invasive PV analysis from CMR detects cardiac response to altered loading conditions in healthy participants and in patients with HCM. Our findings support the use of CMR-derived PV loops for detailed assessment of cardiac thermodynamic performance in relation to interventions affecting preload and afterload.