Chronic high-altitude exposure has been shown to reduce ischemia-reperfusion injury in animal experiments. The objective was to evaluate the clinical protective effect of long-term high-altitude hypoxic exposure for patients undergoing cardiac surgery with cardiopulmonary bypass.
In this retrospective cohort study, data from patients who underwent cardiac procedures between January 2013 and December 2019 at a single center was collected. Patients were divided into highlander group (> 2500 m) and lowlander group (< 1500 m) according to the altitude of their residence. A propensity-score-matched analysis was performed to estimate the association of long-term high-altitude exposure and cardiac surgery outcomes.
In a total of 2085 patients, 128 highlander patients were matched to 248 lowlander patients. The levels of CK-MB and hs-TnI upon arrival at the intensive care unit were lower in the highlander group compared to the lowlander group [70.6 U/L (56.0, 92.6) vs 85.0 U/L (68.5, 113.5), P < 0.001; 6.1 ng/mL (3.3,11.2) vs 7.9 ng/mL (3.6, 14.1), P = 0.011, respectively]. The highlander group also had a lower incidence of acute kidney injury (13.3% vs 21.8%, P = 0.046). The in-hospital mortality in the highlander group was lower than in the lowlander group without statistical significance (0.8% vs 4.0%, P = 0.107).
Long-term high-altitude exposure was associated with less myocardial injury and a lower incidence of acute kidney injury after cardiac surgery.