Exercise testing can unmask right ventricular dysfunction in systemic sclerosis patients with normal resting pulmonary artery pressure

Background: Pulmonary arterial hypertension (PAH) is a frequent complication of systemic sclerosis (SSc). Diagnosis usually occurs late and often after the development of irreversible right heart dysfunction. Exercise testing is increasingly used for assessing right ventricular (RV) function when resting hemodynamics do not account for symptoms. We hypothesized that SSc patients without resting pulmonary hypertension could have impaired exercise capacity and RV contractile reserve with exercise thus unmasking early RV dysfunction and pulmonary vascular disease.

Methods: Treadmill exercise stress echocardiography with concurrent expired gas analysis was performed in 25 SSc patients with normal resting pulmonary arterial pressure (PAP) and healthy controls (n = 50). Additionally, controls and SSc patients were compared to those with established PAH (n = 23). Parameters of RV systolic function (RV fractional area change (FAC), Doppler tissue (DTI) s' velocity, systolic strain and strain rate (S-Sr)) were evaluated at baseline and post-exercise with the difference (Δ) being contractile reserve.

Results: RV contractile reserve was reduced in the SSc group with normal resting PAP, compared with healthy controls (Δs': 6.1 ± 2.3 vs 8.0 ± 2.2 cm s(-1), p < 0.001; and ΔS-Sr: 2.3 ± 0.5 vs 2.6 ± 0.2s(-1), p = 0.02) in association with a significantly higher mean PAP with exercise (25.5 ± 6.6 vs 19.9 ± 7.2 mmHg, p < 0.001). PAH patients demonstrated the lowest levels of contractile reserve (Δs', Δ strain, ΔS-Sr and ΔFAC, all p < 0.05).

Conclusion: Exercise stress testing unmasks reduced RV contractile reserve in SSc patients with normal resting PAP. Subclinical RV dysfunction during exercise may be a surrogate for early pulmonary vascular disease in SSc patients.