Impact of grip strength and gait speed on exercise tolerance in patients with pulmonary hypertension without left heart disease

Patients with pulmonary hypertension (PH) suffer from poor exercise tolerance due to impaired oxygenation and/or reduced cardiac output. However, the relationship between exercise tolerance and physical function remains unclear. The purpose of this study was to investigate the relationship between exercise tolerance and physical function in patients with PH. A total of 94 patients without left heart disease (61.3 ± 14.7 years old, 69.1% females, 22/8/60/4 patients with Group 1/3/4/5 PH) were retrospectively analysed. Physical function was measured using muscle strength (grip strength, knee extension muscle strength), balance function (one-leg standing time), and gait speed within 7 days of cardiac catheterization. Exercise tolerance was measured using the 6-min walking distance (6-MWD). A total of 194 6-MWD measurements and the corresponding physical function were evaluated in 94 patients. Multivariable linear regression analysis using adaptive-LASSO methods indicated that the World Health Organization functional classification, pulmonary vascular resistance, mixed venous oxygen saturation, grip strength, and gait speed were independently associated with the 6-MWD. Low grip strength (< 28 kg for males and < 18 kg for females; adjusted odds ratio and 95% confidence interval: 2.06 [1.30–3.26], p = 0.002), and slow gait speed (< 1.0 m/s for both sexes; 13.33 [3.61–49.19], p < 0.001) were independent predictors of poor exercise tolerance (6-MWD < 440 m) in a logistic regression analysis. Grip strength and gait speed as measures of physical function, pulmonary vascular resistance, and mixed venous oxygen saturation were associated with exercise tolerance in patients with PH without left heart disease.