Cardiopulmonary, biomarkers, and vascular responses to acute hypoxia following cardiac transplantation

Abstract

Previous studies have suggested good adaptation of cardiac transplant (CTx) recipients to exposure to a high altitude. No studies have investigated the cardiopulmonary and biomarker responses to acute hypoxic challenges following CTx. Thirty-six CTx recipients and 17 age-matched healthy controls (HC) were recruited. Sixteen (16) patients (42%) had cardiac allograft vasculopathy (CAV). Cardiopulmonary responses to maximal and submaximal exercise at 21% O2 , 20-minutes hypoxia (11.5% O2 ), and following a 10-minute exposure to 11.5% O2 using 30% of peak power output were completed. Vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), suppression of tumorigenicity 2 (ST2) were measured at baseline and at peak stress. Endothelial peripheral function was assessed using near-infrared spectroscopy. Compared with HC, CTx presented a lesser O2 desaturation both at rest (-19.4±6.8 [CTx] vs -24.2±6.0% O2 [HC], P<0.05) and following exercise (-23.2±4.9 [CTx] vs -26.2±4.7% O2 [HC], P<0.05). CTx patients exhibited a significant decrease in peak oxygen uptake. IL-6 and VEGF levels were significantly higher in CTx recipients in basal conditions but did not change in response to acute stress. CTx patients exhibit a favorable ventilatory and overall response to hypoxic stress. These data provide further insights on the good adaptability of CTx to exposure to high altitude.