In 2014, Mellor and colleagues conducted a study examining cardiac biomarkers at altitude, and their relationship to high pulmonary artery systolic blood pressure (PASP), as well as acute mountain sickness (AMS). Cardiac biomarkers can be used to predict and diagnose several clinical conditions. However, the authors of this study were concerned with the ability of cardiac biomarkers to aid in diagnoses of noncardiogenic conditions at high altitude. The ultimate goal of this research was to assist in the creation of a simplified test (with the use of cardiac biomarkers) to identify High Altitude Pulmonary edema (HAPE), which is particularly difficult condition to detect and diagnose in the field. The focus of this study was placed on two common precursors of this condition (PASP and AMS) and their relation to cardiac biomarkers at altitude. The cardiac biomarkers examined in this study are listed below.
| Cardiac Biomarker | Background Information |
| Natriuretic Peptides
· NT-proBNP · BNP (brain natriuretic peptide) |
· Commonly used for Cardiac Congestive Failure diagnosis
· Stimulated by Hypoxia · Have been associated with pulmonary artery hypertension |
| Hs-CRP (highly sensitive c-reactive protein) | · Used in prediction of Myocardial Infarction and acute coronary syndromes
· Marker of inflammation |
| Hs-cTnT(highly sensitive cardiac troponin T) | · Used in myocardial infarction diagnosis
· Increased with pulmonary hypertensive patients after exercise |
The study consisted of 48 healthy subjects ascending to altitude in La Paz, Bolivia. At sea level (SL), 6 weeks prior to the trek, 20 of the subjects were examined pre and post-exercise (control). When the 48 subjects reached La Paz they embarked on a series ascension days, followed by rest days. Data was collected at three primary altitudes, 3833m, 4450m, and 5129m.
Day 1: arrive and rest La Paz 3681 m
Day 2: ascension to 3833 m
Day 3: rest at 3833 m
Day 4: La Paz 3681 m
Day 5: ascension to 4450 m
Day 6: rest at 4450 m
Day 7: ascension to 4710 m
Day 8: rest at 4710 m
Day 9: ascension to 5129 m
Day 10: rest at 5129 m
Throughout the study, heart rate, blood pressure, oxygen saturation, and AMS scores were recorded twice daily. Venous blood samples and electrocardiography were collected immediately following exercise (marked as ascension above) and the following morning (rest days). The bolded days above identify which days these measures were taken. The venous blood samples were used for the examination of cardiac biomarkers. AMS scores were assessed by a self-report questionnaire.
All cardiac biomarkers were found to be significantly different at varying altitudes. NT-proBNP levels were significantly higher at 5129m rest, compared to SL, but not after exercise. Elevated levels of Hs-cTnT were positively correlated in individuals with a >40mmHg PASP, but had no relation to AMS or severe AMS. Hs-CRP levels were only weakly correlated with BNP and NT-proBNP. BNP and NT-proBNP levels were significantly higher in individuals rated as having AMS and severe AMS. BNP and NT-proBNP were significantly higher in the presence of individuals with >40mmHg PASP.
This study adds to the current body of literature that demonstrates a link between cardiac biomarkers and clinical conditions at altitude. Increased levels of BNP and NT-proBNP were associated with the presence of AMS, severe AMS, and PASP at altitude. Elevated hs-cTnT release was discovered following exercise at altitude and in individuals with high PASP. From a practical standpoint, the results of this study suggest that the use of cardiac biomarkers could eventually aid the detection and diagnosis of HAPE in the field. Although this study only presents their association with high PASP and AMS, both conditions are key components of HAPE. Further research needs to be conducted separating the normal response of cardiac biomarkers at HA from a pathological response.
Mellor A, Boos C, Woods D, et al. Cardiac Biomarkers at High Altitude. High Altitude Medicine & Biology [serial online]. December 2014;15(4):452-458. Available from: Academic Search Alumni Edition, Ipswich, MA. Accessed February 10, 2016.
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