AUTHOR=Mobin Fahim Usshihab , Renaldo Antonio C. , Carrasco Perez Enrique , Jordan James E. , Neff Lucas P. , Williams Timothy K. , Johnson M. Austin , Rahbar Elaheh 

TITLE=Investigating the variability in pressure–volume relationships during hemorrhage and aortic occlusion

JOURNAL=Frontiers in Cardiovascular Medicine

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2023.1171904

DOI=10.3389/fcvm.2023.1171904

ISSN=2297-055X

ABSTRACT=Left ventricle pressure-volume (P-V) relationships are the classical benchmark for studying cardiac mechanics and pumping
function. Perturbations in the P-V relationship (or P-V loop) can be informative and guide the management of heart failure,
hypovolemia, and aortic occlusion. Traditionally, P-V loop analyses have been limited to a single beat P-V loop or an average of
consecutive P-V loops and there are limited tools to evaluate the variations in P-V relationships longitudinally over time. This is
particularly important when studying acute and transient hemodynamic and cardiac events, such as active hemorrhage or aortic
occlusion. In this study, we aimed to investigate the variability in P-V relationships during hemorrhagic shock and aortic occlusion,
by leveraging on a previously published porcine hemorrhage model. Briefly, swine were instrumented with a P-V catheter in the
left ventricle of the heart and underwent 25% total blood volume hemorrhage over 30 minutes, followed by either Zone 1 complete
aortic occlusion (i.e., REBOA), Zone 1 endovascular variable aortic control (EVAC), or no occlusion, as a control, for 45 minutes.
Preload-independent metrics of cardiac performance were obtained at predetermined time points by performing inferior vena
cava occlusion (IVCO) during a ventilatory pause. Continuous P-V loop data, and other hemodynamic flow and pressure
measurements were collected in real-time using a multi-channel data acquisition system.
We developed a custom algorithm to quantify the time-dependent variance in both load-dependent and independent cardiac
parameters from each P-V loop. As expected, all pigs displayed a significant decrease in end-systolic pressures and volumes, after
hemorrhage. The variability in response to hemorrhage was consistent across all three groups. However, upon introduction of
REBOA, we observed significantly high levels of variability in both load-dependent and independent cardiac metrics such as ESP, ESV,
and elastance. For instance, pigs receiving REBOA experienced a 342% increase in ESP from hemorrhage, while pigs receiving EVAC
experienced only 188% increase. The level of variability within the EVAC group was consistently less than the REBOA group, which
suggests that the EVAC group may be more supportive of maintaining healthier cardiac performance than complete occlusion with
REBOA.