# Right Ventricular Free Wall Strain in Healthy Lowlanders and Highlanders—A Case-Control Study

## TL;DR

The study found that highlanders have higher pulmonary pressure but similar right ventricular function compared to lowlanders, suggesting adaptation rather than heart dysfunction.

## Contribution

This study introduces speckle-tracking-derived strain analysis to compare right ventricular function in highlanders and lowlanders.

## Key findings

- RV free wall strain did not differ significantly between highlanders and lowlanders.
- Conventional RV indices like RV FAC and TAPSE showed significant differences between groups.
- Highlanders with and without risk for pulmonary hypertension had similar RV function metrics.

## Abstract

Background/Objectives: It is widely acknowledged that healthy highlanders (HL) present with significantly higher pulmonary arterial pressure (PAP) compared to healthy lowlanders (LL). However, whether this elevated PAP solely signifies a response to hypoxia at altitude or is also linked to right ventricular (RV) dysfunction is still unknown. Therefore, we assessed RV function in HL and LL using speckle-tracking-derived strain analysis. Methods: This case-control study evaluates echocardiographic RV free wall strain (RVFWS) in LL and HL in Kyrgyzstan. A RVFWS over −20% for men and a RVFWS of −21% for women were considered indicators of RV dysfunction. Subgroup analysis included individuals with and without risk for pulmonary hypertension (PH), defined as a TRV > 2.8 m/s. Results: A total of 59 participants (21 LL, 38 HL), with a mean ± SD age of 43 ± 8 versus 48 ± 10 years, were included and assessed at their living altitude. RVFWS in HL and LL was −27.3% ± 4.7 versus −27.0% ± 6.0 (mean difference 0.13%, 95%CI −2.65 to 2.92, p = 0.852). The conventional RV indices RV FAC (42% ± 6 vs. 38% ± 8), TAPSE (2.2 cm ± 0.2 vs. 2.0 cm ± 0.3), and TDI S’ (14.2 cm/s ± 1.9 vs. 12.1 cm/s ± 1.8), however, did differ significantly between LL and HL. HL with and without risk for PH did not differ in RVFWS and in the conventional RV indices. Conclusions: Despite significant differences in conventional RV markers, healthy highlanders generally did not differ in RVFWS compared with lowlanders, indicating maintained RV systolic function at high altitude. Our findings suggest that elevated PAP in HL reflects adaptation rather than RV dysfunction, underscoring the need for refined diagnostic criteria for clinically relevant high-altitude pulmonary hypertension.