Decreased right ventricular contractile reserve in patients with Chronic Mountain Sickness

Background: Chronic Mountain Sickness (CMS) disease is characterized by increase in systolic pulmonary arterial pressure (PASP) during mild effort. Aim: To evaluate left and right ventricular systolic function and their relationship with PASP increase during stress in CMS. Methods: In La Paz (Bolivia, 3600 m s.l.), we evaluated 31 male CMS (age= 54+10 yrs) and 30 male healthy high-altitude dwellers (controls, C; age= 45+10 yrs) at rest and exercise. Upright bicycle exercise (up to 50 Watts) stress echo was performed with integrated 2D (Ejection Fraction, EF, Simpson rule), peak Systolic Velocity from tissue Doppler imaging at the tricuspid annulus (PSVtdi) and Doppler (PASP assessment from peak velocity of tricuspid regurgitation jet) evaluation. Results: CMS patient showed higher PASP at rest (CMS=27.6+6 vs C=24.3+4 mmHg, p=.02) and at peak stress (CMS=44+12 vs C=33+7 mmHg, p,.001). Right ventricular function was similar at rest (PSVtdi: CMS=13.3+2.3 vs C=13+2.6 cm. s-1, p=ns) but lower in CMS at peak stress (CMS=12+1 vs C=15+3 cms-1, p,.0001) (see figure). EF was similar in CMS at rest (CMS=63+6 vs C=66+6%, p=ns) and at peak stress (CMS=67+6 vs C=66+8%, p=ns). The exercise-induced increase in PASP was correlated with PSVtdi in C (R= 0.6, p=.03), but not in CMS (R=0.1, p=ns). Conclusion: When compared to controls, CMS patients show an increase in PASP during exercise associated with a preserved left ventricular and decreased right ventricular contractile reserve.