REBOA is associated with more variability in cardiac performance and physiologic response compare to partial aortic occlusion after hemorrhage

Introduction:: Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is a lifesaving intervention designed to mitigate non-compressible torso hemorrhage. By introducing a full aortic occlusion with REBOA one is able to minimize internal bleeding, but this procedure can only be applied for short durations due to the major risk of ischemia-reperfusion injury (IRI) post-occlusion. Partial occlusive strategies, like endovascular variable aortic control ( EVAC) mitigate these risks by reducing the level of occlusion seen in full REBOA, allowing for longer lengths of intervention time and curbing IRI. Left ventricle pressure-volume (P-V) relationships are the classical benchmark for studying cardiac mechanics and pumping function. Perturbations to 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 commercially available software that either provides information from a single beat P-V loop or generates an ensemble average of consecutive P-V loops. While there are several algorithms to obtain single-beat estimations of end-systolic and end-diastolic pressure volume relations (i.e., ESPVR and EDPVR), there remains a need to better 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. We leveraged a previously published porcine hemorrhage model to investigate the individual variability in P-V relationships during hemorrhagic shock and aortic occlusion.

Materials and Methods::


Results, Conclusions, and Discussions:: Results and Discussion:

At baseline (T0), all animal groups should have been similar, and indeed our results confirm that the inherent physiologic variability in CO and P-V relationships is relatively low. On average the CO is 4.2 ± 1.9 L/min across all animals. At the end of 25% hemorrhage (T30), there were significant decreases in ESP, ESV, EDP, EDV, and SW. Conversely, statistically significant increases in, HR, EJF and Ees (the slope of linear ESPVR obtained under load independent conditions) were observed, with the REBOA group displaying the highest variability in these indices. CO was not statistically different than baseline, indicating that the animal’s natural physiologic response is to preserve CO during acute hemorrhage. At the end of the intervention phase (T74), the largest differences in cardiac function between EVAC and REBOA groups were observed. In the control group, ESP, EDV and EDP were restored to near baseline levels, but CO was generally higher than baseline. In the REBOA group, there was a restoration of SV, EJF, ESV, EDV EDP and significant increases in SW, HR, CO, Ea, ESP when compared to baseline. Furthermore, a doubling of Ees was observed (with high variability), implying considerable changes in left ventricular contractility. In the EVAC group, no significant differences in cardiac function were noted compared to baseline and less variability was observed in comparison to the REBOA group. This implies a large variability the impact of REBOA on cardiac function and that the REBOA intervention can lead to potentially damaging effects on the heart and its performance compared to EVAC.

Conclusions: In this study we developed an algorithm to perform beat-to-beat analysis of P-V loops under load-independent and load-dependent conditions. We evaluated the effects of EVAC and REBOA interventions on cardiac function and found that REBOA was associated with significantly increased variability and worse cardiac performance suggesting that partial aortic occlusion strategies are associated with less drastic changes in cardiac functional metrics. Further studies are needed to determine the relationship between varying degrees of partial occlusion and cardiac performance at milder and more severe hemorrhage conditions.


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