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Objective: Despite advances in design, modern ventricular assist device (VAD) placement involves median sternotomy, cardiopulmonary bypass, and is associated with infectious/embolic complications. Accordingly, innovative approaches to assistive therapies for ischemic cardiomyopathy (ICM) remain in great demand. In this study, we examine the feasibility and function of a novel minimally invasive, off-pump epicardial assist device in a porcine ICM model.
Methods: Five male Yorkshire swine underwent selective ligation of the circumflex artery and its branches to create a 23.8±1.5% posterolateral infarct. Twelve weeks post-infarct, all animals underwent left mini-thoracotomy. A custom inflatable bladder was positioned over the epicardial surface of the infarct and firmly secured to surrounding borderzone myocardium with polypropylene mesh and minimally-invasive mesh tacks (Figure 1a). The inflation port was externalized through the chest wall and connected to an external gas pulsation system which actively inflated and deflated (Figure 1b-c, respectively) the bladder in synchrony with the cardiac cycle. All animals then underwent pressure-gated 3D cardiac MRI to assess device and ventricular function. Post-mortem, the heart was examined for evidence of mesh dehiscence, device damage, coronary injury, and ventricular perforation.
Results: All subjects successfully underwent off-pump placement of the novel epicardial assist device via mini-thoracotomy. Total operative time was under 30 minutes in all cases. Ejection fraction (EF) significantly improved from 29.1±4.8% to 39.6±4.23% (p<0.001) when compared to pre-treatment. End-systolic volume decreased (76.6±13.3ml vs 62.4±12.0ml, p<0.001) and stroke volume increased (28.6±3.4ml vs 37.9±3.1ml, p<0.05) when assisted. No change was noted in end-diastolic volume (105.1±11.4 vs 100.3±12.7). On post-mortem examination, mesh fixation and device position were excellent in all cases. No complications were noted.
Conclusions: Directed epicardial assistance improves global ventricular function in a porcine ICM model, and may provide a safe alternative to currently available invasive VAD therapies. Minimally invasive, off-pump placement of the novel assist device was easy and technically uncomplicated. Further, the technique used for device positioning and fixation suggests an entirely thoracoscopic approach is possible.