Exercise gas exchange in continuous-flow left ventricular assist device recipients

Exercise ventilation/perfusion matching in continuous-flow left ventricular assist device recipients (LVAD) has not been studied systematically. Twenty-five LVAD and two groups of 15 reduced ejection fraction chronic heart failure (HFrEF) patients with peak VO 2 matched to that of LVAD (HFrEF-matched) and !14 ml/kg/min (HFrEF!14), respectively, underwent cardiopulmonary exercise testing with arterial blood gas analysis, echocardiogram and venous blood sampling for renal function evaluation. Arterial-end-tidal PCO 2 difference (P(a-ET)CO 2 ) and physiological dead space-tidal volume ratio (VD/VT) were used as descriptors of alveolar and total wasted ventilation, respectively. Tricuspid annular plane systolic excursion/pulmonary artery systolic pressure ratio (TAPSE/PASP) and blood urea nitrogen/creatinine ratio were calculated in all patients and used as surrogates of right ventriculo-arterial coupling and circulating effective volume, respectively. LVAD and HFrEFmatched showed no rest-to-peak change of P(a-ET)CO 2 (4.52.4 vs. 4.32.2 mm Hg and 4.11.4 vs. 3.82.5 mm Hg, respectively, both p >0.40), whereas a decrease was observed in HFrEF!14 (6.53.6 vs. 2.82.0 mm Hg, p <0.0001). Rest-to-peak changes of P(a-ET) CO 2 correlated to those of VD/VT (r = 0.70, p <0.0001). Multiple regression indicated TAPSE/PASP and blood urea nitrogen/creatinine ratio as independent predictors of peak P (a-ET)CO 2 . LVAD exercise gas exchange is characterized by alveolar wasted ventilation, i.e. hypoperfusion of ventilated alveoli, similar to that of advanced HFrEF patients and related to surrogates of right ventriculo-arterial coupling and circulating effective volume.