Prospective evaluation of ventricular assist device risk scores' capacity to predict cardiopulmonary exercise parameters

Exercise capacity following ventricular assist device implantation via thoracotomy with outflow cannula anastomosis to the descending aorta

Left ventricular assist device (LVAD) implantation via left lateral thoracotomy with outflow cannula anastomosis to the descending aorta is an alternative technique that avoids anterior mediastinal planes and requires a single incision. This study compares changes in exercise capacity following LVAD implantation with outflow cannula anastomosis to the descending aorta versus ascending aorta. Adult patients who received a continuous flow centrifugal LVAD implantation and completed both pre- and postimplantation cardiopulmonary exercise tests (CPETs) and or 6-minute walk tests (6MWT) were included. Change in CPET parameters (maximum oxygen intake: vO₂ max, oxygen uptake efficiency ratio: OUES, ventilatory efficiency ratio: vE/vCO₂ Slope) and 6MWT distance were compared between ascending and descending aorta anastomosis groups. Ascending and descending aorta anastomosis cohorts included 59 and 14 patients, respectively. Pre- and postimplantation CPETs were performed 63 ± 12 days before and 216 ± 17 days following implantation. The improvement in CPET parameters (vO₂ max, OUES, vE/vCO₂ Slope) or 6MWT distance was not significantly different between the ascending and descending aorta anastomosis groups. This study found no significant difference in the improvement of CPET parameters or 6MWT distance between LVAD implantation via thoracotomy with outflow cannula anastomosis to descending aorta and standard implantation via sternotomy with outflow cannula anastomosis to ascending aorta.

Exercise physiology in left ventricular assist device patients: insights from hemodynamic simulations

Left ventricular assist devices (LVADs) assure longer survival to patients, but exercise capacity is limited compared to normal values. Overall, LVAD patients show high wedge pressure and low cardiac output during maximal exercise, a phenomenon hinting at the need for increased LVAD support. Clinical studies investigating the hemodynamic benefits of an LVAD speed increase during exercise, ended in inhomogeneous and sometimes contradictory results. The native ventricle-LVAD interaction changes between rest and exercise, and this evolution is complex, multifactorial and patient-specific. The aim of this paper is to provide a comprehensive overview on the patient-LVAD interaction during exercise and to delineate possible therapeutic strategies for the future. A computational cardiorespiratory model was used to simulate the hemodynamics of peak bicycle exercise in LVAD patients. The simulator included the main cardiovascular and respiratory impairments commonly observed in LVAD patients, so as to represent an average hemodynamic response to exercise. In addition, other exercise responses were simulated, by tuning the chronotropic, inotropic and vascular functions, and implementing aortic regurgitation and stenosis in the simulator. These profiles were tested under different LVAD speeds and LVAD pressure-flow characteristics. Simulations output showed consistency with clinical data from the literature. The simulator allowed the working condition of the assisted ventricle at exercise to be investigated, clarifying the reasons behind the high wedge pressure and poor cardiac output observed in the clinics. Patients with poorer inotropic, chronotropic and vascular functions, are likely to benefit more from an LVAD speed increase during exercise. Similarly, for these patients, a flatter LVAD pressure-flow characteristic can assure better hemodynamic support under physical exertion. Overall, the study evidenced the need for a patient-specific approach on supporting exercise hemodynamics. In this frame, a complex simulator can constitute a valuable tool to define and test personalized speed control algorithms and strategies.

Cardiopulmonary Exercise Test in heart failure: A Sine qua non

A robust literature, over the last years, supports the indication of cardiopulmonary exercise testing (CPET) in patients with cardiovascular diseases. Understanding exercise physiology is a crucial component of the critical evaluation of exercise intolerance. Shortness of breath and exercise limitation is often treated with an improper focus, partly because the pathophysiology is not well understood in the frame of the diagnostic spectrum of each subspecialty. A vital field and research area have been cardiopulmonary exercise test in heart failure with preserved/reduced ejection fraction, evaluation of heart failure patients as candidates for LVAD-Implantation, as well as for LVAD-Explantation and ultimately for heart transplantation. All the CPET variables provide synergistic prognostic discrimination. However, Peak VO2 serves as the most critical parameter for risk stratification and prediction of survival rate.