A Cardiac and a Kidney Transplant Patient Above 6000 Meters in Bolivia

Ambulatory Blood Pressure at Sea Level and High Altitude in a Climber with a Kidney Transplant and Hypertension

Background and Objectives: High altitude may increase blood pressure (BP) and the kidney plays an important role in acclimatization. Little is known about how transplanted kidneys respond to the hypoxic stress at high altitude. We compared 24 hour ambulatory BP in a climber with a kidney transplant and hypertension at sea level and at high altitude (2860-4300 m). Methods: Welch-Allyn ABPM 6100 monitor was used to collect heart rate, systolic BP (SBP), and diastolic BP every 30 minutes while awake, and hourly while asleep. BP was monitored for 49 hours at sea level and for 53 hours at 2860-4300 m. Results: Overall mean SBP did not differ between altitudes. At high altitude, the participant's mean nocturnal BP increased, but this "reverse dipping" pattern was not observed at sea level. The participant had no evidence of altitude illness or infectious complications at high altitude. Conclusions: This case builds on previous reports that kidney transplant recipients may safely travel to high altitude. Further study is required to determine the generalizability to other travelers with kidney transplant and/or underlying hypertension, and the clinical significance of short-term elevated nocturnal BP at high altitude.

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

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.

Improved survival in heart transplant patients living at high altitude

OBJECTIVE

Higher altitudes are associated with chronic hypoxia and elevated pulmonary vascular resistance, both potentially detrimental to patients requiring heart transplantation. The purpose of the present study was to determine whether altitude negatively affects survival among patients undergoing heart transplantation.

METHODS

The United Network of Organ Sharing database for adult patients undergoing heart transplantation from 1990 to 2008 (n = 36,529) was analyzed, and each patient was assigned an altitude according to their home ZIP code. Survival was compared between patients at less than 2000 ft, 2000 or more to less than 4000 ft, and 4000 ft or more. Adjusted survival was calculated using Cox proportional hazards analysis with propensity-matched stratification.

RESULTS

Patients living at above 2000 ft had a 16% reduction in the risk of death at 1 year after transplant (P = .006) compared with those at lower altitudes. At 5 and 10 years, the risk reduction was 6% (P = .21) and 6% (P = .114), respectively. Among patients living above 4000 ft, the 1-, 5-, and 10-year reduction in the risk of death was 20% (P = .022), 12% (P = .057), and 15% (P = .0052) compared with those living below 2000 ft, respectively. Patients at high altitude had a lower incidence of diabetes, used tobacco less often, and accounted for the greatest proportion of status 2 heart transplants. Comparing the factors predicting survival at high and low altitudes, patients with a status 1A listing had improved outcomes at higher altitudes.

CONCLUSIONS

Patients living above 2000 ft have improved survival after heart transplantation, an advantage even more pronounced at 4000 ft. Although the mechanism of protection remains unclear, the findings might reflect differences in pre-2006 organ allocation.