MEDEX 2015: The key role of cardiac mechanics to maintain biventricular function at high altitude

New Findings

What is the central question of this study? This study is the first investigating the effects of high‐altitude trekking on biventricular mechanics including measurements of left ventricular (LV) subendocardial and subepicardial function. What is the main finding and its importance? We provide new evidence that an increased contractility and untwisting efficiency, a key element of diastolic function, probably play a key role to preserve cardiac function during high‐altitude trekking. Persistent increased loading conditions during several weeks at high altitude may have a key role in the apparition of LV or RV dysfunctions.

Abstract

Aims

Cardiac responses to acute hypoxic exposure have been deeply investigated. We analyzed the effects of high‐altitude trekking (i.e. prolonged hypoxic exposure) on the biventricular function including the evaluation of subendocardial and subepicardial functions in the left ventricle (LV).

Methods and results

Resting evaluations of LV and right ventricular (RV) function and mechanics were assessed by Speckle Tracking Echocardiography on twenty subjects at sea level and at high altitude (5085 m, after a 10‐day ascent). Pulmonary artery systolic pressure (PASP) was increased at high altitude (sea level: 13.1 ± 5.9 mmHg; high altitude: 26.6 ± 10.8 mmHg, p < 0.001). LV volumes were decreased whereas RV volumes were increased at high altitude. Alterations in PASP and cardiac volumes were correlated to hypoxemia. We observed neither RV nor LV systolic dysfunction, including analysis of LV subendocardial and subepicardial function. LV systolic strain rates were enhanced at high altitude. Transmitral and transtricuspid diastolic filling ratios were decreased at high altitude. Diastolic apical rotational rate, untwisting rate and untwisting rate/peak twist ratio (i.e. untwisting efficiency) were enhanced at high altitude.

Conclusion

We observed no echocardiographic signs of LV and RV pathological dysfunctions at rest at high altitude. In contrast, our data highlighted major changes in the LV mechanics with an increased LV contractility and a higher untwisting efficiency at high altitude. Biventricular interaction, alterations in loading conditions and an increase in plasma catecholamine concentration may partly explain these modifications. Thus, we demonstrated that LV mechanics (i.e. increased strain rates and untwisting efficiency) have a key role to preserve cardiac function during high‐altitude trekking.

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