In vitro validation of a passive left ventricular assist device

Cardiogenic shock, represents a dangerous consequence of myocardial infarction, severe cardiomyopathy, or mechanical obstruction or compression of the heart. The mismatch between the elastances of the failed left ventricle and the normal aorta limits the energy transfer between the pump and the arterial load worsening the just critical condition.. Since it is not possible to increase the ventricular elastance, a possible intervention to recover a better mechanical coupling is to decrease the aortic one, by inserting a dumper in aorta. We tested this proposal by inserting an intra-aortic balloon filled with helium in a previously validated simulator of the cardiovascular system. Different conditions of mismatch between ventricle and aorta and different filling pressures of the balloon were simulated. Aortic pressures and flows were measured with a polygraphic system (EP-12, Esaote, Italy) and an AD converter (Light System, Sparkbio, Italy). Results show that increasing step by step the helium pressure in the balloon, the shape of arterial pressure pulse changes both for systolic and diastolic values, with an overall increasing of the mean pressure. The maximum positive effect is obtained with a balloon pressure slightly higher than the mean aortic one. This “pure passive biomechanical approach” seems to be useful and easy to apply. To evaluate the net benefit in clinical conditions an “in vivo” protocol is in progress and preliminary results support our in-vitro findings.