Rapid Fire Abstracts
Karin Pola, MD
MD, PhD student
Lund University, Skåne University Hospital Lund, Department of Clinical Sciences Lund, Clinical Physiology, Lund, Sweden, Sweden
Karin Pola, MD
MD, PhD student
Lund University, Skåne University Hospital Lund, Department of Clinical Sciences Lund, Clinical Physiology, Lund, Sweden, Sweden
Charlotte Burup Kristensen, MD, PhD
MD, PhD
University hospital of Copenhagen, Copenhagen, Denmark, Denmark
Will D. Watson, BSc
Clinical Lecturer
University of Cambridge, United Kingdom
Peregrine Green, MD, PhD
Researcher
University of Oxford, United Kingdom
Betty Raman, MBBS FRACP DPhil
Associate Professor of Cardiovascular Medicine
University of Oxford, United Kingdom
Stefan Neubauer, MD, PhD
Professor
Oxford Centre for Clinical Magnetic Resonance Research, United Kingdom
Oliver Rider, PhD
Consultant Cardiologist
University of Oxford Centre for Clinical Magnetic Resonance, United Kingdom
Christian Hassager, MD, PhD
Professor
University hospital of Copenhagen, Copenhagen, Denmark, Denmark
Rasmus Møgelvang, MD, PhD
Professor
Copenhagen University, Copenhagen, Denmark, Denmark
Håkan Arheden, MD, PhD
MD, PhD, Professor
Lund University and Skåne University Hospital, Lund, Sweden, Sweden
Per M Arvidsson, MD, PhD
Postdoctoral researcher
Lund University, Sweden
Pressure-volume (PV) analysis provides unique insights into hemodynamics, including myocardial efficiency and oxygen consumption, and can now be computed non-invasively using standard cardiac magnetic resonance (CMR) cine images (1,2). Previous studies have validated this method in healthy and failing hearts (3,4).
Alterations in preload and afterload affect ventricular function and may unmask pathology through effects on pressure-volume relations, although this remains to be evaluated using non-invasive methods. The aim of this study was therefore to assess the effects of changing preload and afterload on non-invasive PV loops in healthy controls and in patients with hypertrophic cardiomyopathy (HCM).
Methods:
In total, n=32 participants underwent CMR with acquisition of short-axis cine images and concurrent brachial blood-pressure measurements (Figure 1A). Healthy controls (n=12) and patients with HCM (n=12, of which n=4 were obstructive) were assessed at baseline and immediately after rapid intravenous infusion of 1.5-2 liters isotonic saline. Another group of healthy subjects (n=8) was assessed at baseline and during GTN infusion.
Pressure-volume loops were calculated using Segment (https://medviso.com/segment/), for analysis of contractility, ventricular efficiency, potential energy, and stroke work (Figure 1B). Statistical analysis was conducted in GraphPad Prism v.10.2.0 using the Wilcoxon test or paired t-test for paired comparisons within each group.
Results:
After saline infusion, controls and patients with HCM increased heart rate, cardiac output (Table 1), ventricular efficiency and stroke work, whereas contractility and potential energy remained unchanged (Figure 1C-D and 1F). Increased stroke work in controls was primarily driven by increased stroke volume, resulting in a widening of the PV loop. Conversely, increased stroke work in patients was mainly secondary to increased systolic blood pressure, and thereby a taller PV loop (Table 1), suggesting a decreased compliance in HCM consistent with a restrictive phenotype.
Infusion of GTN in healthy subjects resulted in a decrease in blood pressure, end-diastolic and end-systolic volumes, stroke volume, potential energy and stroke work. There was an increase in heart rate and ventricular efficiency, while cardiac output and contractility remained unchanged (Table 1 and Figure 1E and 1G).
Conclusion: Non-invasive pressure-volume analysis detects cardiac response to altered loading conditions. This may be a novel approach to assessing myocardial compliance, and the method may be used on data already acquired in previous studies.
