A computational model to simulate physical exercise in heartfailure condition with a LVAD.

Objectives: Aim of the work is the development of a computational cardiorespiratory model able to simulate upright bicycle exercise (BE) of different intensity levels (from rest to 75 watts) in both physiological (PH) and heart failure (HF) conditions. Methods & Materials: The simulator is a lumped parameter model providing the representation of: left/right hearts, systemic and pulmonary circulations, ventilatory mechanics, gas exchange (lobes-blood), gas transport (bloodtissues), baroreflex and metabolic controls. An additional module reproduces a continuous left ventricular assist device characteristics (LVAD) in terms of pressure-flow relationship. BE was reproduced increasing the regional oxygen uptakes according to BE level and including the baroreflex resetting mechanism in the model. Results: Specific simulations were conducted in three different conditions: PH, HF, and HF+LVAD. HF was simulated by decreasing the end-systolic left ventricular elastance from 4.6 to 1.1 mmHg/cm3. Results evidence differences among the three groups i.e. from rest to 75 watts: cardiac outputs (l/min) were 5.9-10 for PH, 3.4-6.6 for HF, and 4-7.8 for HF+LVAD; flows (l/min) through exercising regions were 0.84-6.3 for PH, 0.7-3.1 for HF, 0.8-3.9 for HF+LVAD; legs arteriovenous oxygen differences (mlO2/dl blood) were 7-15.9 for PH, 10-19.2 for HF, 8.8-16.3 for HF+LVAD. Conclusions: PH, HF conditions were set and compared with literature data. The model permits to simulate BE for both PH and HF. The addition of LVAD has a positive effect in terms of CO increment and regional perfusion. In this sense this tool is a first attempt to study LVAD performance in different conditions, evidencing the need to provide an assist device able to detect and automatically adapt to the change of patients\u27 needs. Acknowledgments: this work was developed within FP7 SensorART project (GA n. 248763)