Myocardial Performance Index in Subjects Susceptible to High-Altitude Pulmonary Edema

Abstract

Objective A recent study concerning high-altitude pulmonary edema (HAPE), a non-cardiogenic pulmonary edema, suggested that it is initially a hydrostatic-type pulmonary edema. We suspect that some extent of cardiac insufficiency may likely relate to the mechanism of the development of this disease. Methods By Doppler echocardiography, the Tei index (a new quantitative index proposed for the evaluation of global myocardial performance) and the systolic pulmonary artery pressure (sPAP) were measured before and after 30 minutes of hypoxic breathing. Patients Eleven HAPE-susceptible subjects (HAPE-s) and nine HAPE-resistant subjects (HAPE-r).Results The results of Tei index indicated an enhanced left myocardial performance but an impaired right performance in HAPE-s during hypoxic breathing. The sPAP of HAPE-s was significantly increased after hypoxic breathing, which was not correlated with the heart functions such as right ventricular (RV) Tei index, cardiac index (CI), percent ejection fraction (EF%) and percent fractional shortening (FS%) under hypoxic condition. Comparatively, the HAPE-r subjects did not show such significant changes of Tei index after hypoxic breathing. The results suggested that a paradoxical myocardial performance, in a format of an augmented left ventricular (LV) in contrast to an attenuated RV, was observed in the HAPE-s exposed to acute hypoxia. Conclusion The responses of the left and right myocardial performances to hypoxia may be involved in the pathogenesis of HAPE.

Preserved right ventricular function but increased right atrial contractile demand in altitude-induced pulmonary hypertension

“…Data regarding the effect of acute high-altitude exposure on RV function and structure are sparse and conflicting. While some studies report that an acute hypoxia-induced increase in RV afterload leads to an improved contractility [17], others found no change [18] or even an impaired contractility [19][20][21]. The discrepancies in the existing literature could be related to the considerable differences between methods and research designs.…”

Right Ventricle and High Altitude

“…However, it has been suspected that some extent of cardiac insuffi ciency may favour the development of HAPE. The Tei index of RV function measured by Doppler echocardiography before and after 30 min of hypoxic breathing in 11 HAPE-susceptible subjects compared to nine HAPE-resistant subjects evidenced an enhanced left ventricular myocardial performance but an impaired right ventricular performance in HAPEsusceptible subjects [ 21 ]. Elite swimmers following a "Living High Training Low" procedure during 13 days between 2,500 and 300 simulated altitude showed a slight increase in the RV/LV diameters ratio at echocardiography, suggesting a slight dilatation of the right ventricle without alteration of contractile function [ 22 ].…”

Left Ventricular Function during Acute High-Altitude Exposure in a Large Group of Healthy Young Chinese Men

“…This is in keeping with previous findings that suggested that LV systolic function was improved in hypoxic healthy volunteers [ 1 – 3 , 22 , 23 ] and even in studies referring to adults and children exposed to high altitude [ 21 , 24 ]. The improved cardiac systolic function in hypoxic environments allows for the output of the maximum amount of blood to transfer a sufficient amount of oxygen to support the metabolic demands of a body challenged by hypoxic stress [ 9 ]. As expected, the present data did show an improvement in cardiac output in all subjects, due to their elevated HR and SV.…”