The effect of minimally invasive surgical aortic valve replacement on postoperative pulmonary and skeletal muscle function

Abstract

NEW FINDINGS: What is the central question of this study? An increasing number of patients are in need of aortic valve replacement. It remains unresolved how surgical aortic valve replacement affects the cardiopulmonary and muscle function during exercise. What is the main finding and its importance? Early after the surgical replacement of the aortic valve a significant decline in pulmonary function was observed, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. These date reiterate, despite restoration of aortic valve function, the need of a tailored rehabilitation program for the respiratory and peripheral muscular system.

ABSTRACT: Introduction Suboptimal post-operative improvements in functional capacity are often observed after minimally invasive aortic valve replacement (mini-AVR). It remains to be studied how AVR affects the cardiopulmonary and skeletal muscle function during exercise to explain these clinical observations and to provide a basis for improved/tailored post-operative rehabilitation. Methods Twenty-two patients with severe aortic stenosis (AS) (aortic valve area (AVA) < 1.0 cm²) were pre-operatively compared to 22 healthy controls during submaximal constant-workload endurance-type exercise for: oxygen uptake (V̇O2 ), carbon dioxide output (V̇CO2 ), respiratory gas exchange ratio, expiratory volume (VE), ventilatory equivalents for O2 (VE/V̇O2 ) and CO2 (V̇E/V̇CO2 ), respiratory rate (RR), tidal volume (Vt ), heart rate, oxygen pulse (V̇O2 /HR), blood lactate, Borg ratings of perceived exertion (RPE) and exercise-onset V̇O2 kinetics. These exercise tests were repeated at five and 21 days after AVR surgery (n = 14), next to echocardiographic examinations. Results RER, ventilatory equivalents (VE/V̇O2 and VE/V̇CO2 ) were significantly elevated, V̇O2 and V̇O2 /HR were significantly lowered, and exercise-onset V̇O2 kinetics were significantly slower in AS patients vs. healthy controls (p < 0,05). Although the AVA was restored by mini-AVR in AS patients, VE/V̇O2 and VE/V̇CO2 further worsened significantly within five days after surgery, accompanied by elevations in Borg RPE, VE, RR and lowered Vt . At 21 days after mini-AVR exercise-onset V̇O2 kinetics further slowed significantly (p < 0,05). Conclusion A decline in pulmonary function was observed early after mini-AVR surgery, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. Therefore, a tailored rehabilitation program should include training modalities for the respiratory and peripheral muscular system.