Acute Changes in Pulmonary Artery Pressures Due to Exercise and Exposure to High Altitude

left ventricularIn various forms of pulmonary hypertension, an association between elevated pulmonary artery pressures and abnormal left ventricular (LV) diastolic function has been proposed. Ventricular interaction with a shift of the septum toward the LV as a consequence of right ventricular pressure overload has been suggested as the primary cause of LV diastolic dysfunction.

At high altitude, not only acute hypoxia-induced pulmonary hypertension but also changes of the transmitral inflow pattern suggestive of impaired LV diastolic function have been described. In accordance to chronic right-sided pressure overload, ventricular interaction has been discussed as a cause for the observed alteration in LV diastolic function. Recently, a new concept of compensated altitude-induced diastolic dysfunction was proposed because changes in diastolic function at high altitude were mainly related to an increase in the atrial phase of LV filling.

In high-altitude pulmonary edema-susceptible (HAPE-S) subjects, an abnormal pulmonary vascular response occurs not only at high altitude but also under normoxic conditions during submaximal levels of exercise. Concurrent data on LV diastolic function, however, are limited to evaluation of mitral inflow patterns recorded during exercise.

Prophylactic administration of the phosphodiesterase inhibitor tadalafil or the corticosteroid dexa-methasone has been shown to effectively reduce altitude-induced pulmonary hypertension and prevent high-altitude pulmonary edema (HAPE). To date, assessment of LV diastolic function at high altitude has not been studied under the influence of HAPE prophylaxis.

To provide more detailed information on LV diastolic function in the presence of acute pulmonary hypertension and to evaluate potential consequences of therapeutic intervention, we investigated HAPE-S subjects randomized to tadalafil, dexamethasone, or placebo, and control subjects without a history of HAPE. Subjects were assessed by Doppler echocardiography at rest and during submaximal exercise, at low as well as at high altitude.

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