Reduced pulmonary vascular reserve during stress echocardiography in confirmed pulmonary hypertension and patients at risk of overt pulmonary hypertension

Noninvasive estimation of systolic pulmonary artery pressure (SPAP) during exercise stress echocardiography (ESE) is recommended for pulmonary hemodynamics evaluation but remains flow-dependent. Our aim was to assess the feasibility of pulmonary vascular reserve index (PVRI) estimation during ESE combining SPAP with cardiac output (CO) or exercise-time and compare its value in three group of patients: with invasively confirmed pulmonary hypertension (PH), at risk of PH development (PH risk) mainly with systemic sclerosis and in controls (C) without clinical risk factors for PH, age-matched with PH risk patients. We performed semisupine ESE in 171 subjects: 31 PH, 61 PH at risk and 50 controls as well as in 29 young, healthy normals. Rest and stress assessment included: tricuspid regurgitant flow velocity (TRV), pulmonary acceleration time (ACT), CO (Doppler-estimated). SPAP was calculated from TRV or ACT when TRV was not available. We estimated PVRI based on CO (peak CO/SPAP*0.1) or exercise-time (ESE time/SPAP*0.1). During stress, TRV was measurable in 44% patients ACT in 77%, either one in 95%. PVRI was feasible in 65% subjects with CO and 95% with exercise-time (p < 0.0001). PVRI was lower in PH compared to controls both for CO-based PVRI (group 1 = 1.0 ± 0.95 vs group 3 = 4.28 ± 2.3, p < 0.0001) or time-based PVRI estimation (0.66 ± 0.39 vs 3.95 ± 2.26, p < 0.0001). The proposed criteria for PH detection were for CO-based PVRI ≤ 1.29 and ESE-time based PVRI ≤ 1.0 and for PH risk ≤ 1.9 and ≤ 1.7 respectively. Noninvasive estimation of PVRI can be obtained in near all patients during ESE, without contrast administration, integrating TRV with ACT for SPAP assessment and using exercise time as a proxy of CO. These indices allow for comparison of pulmonary vascular dynamics in patients with varied exercise tolerance and clinical status.