Exercise stress echocardiography has not been recommended in the diagnostic workup of pulmonary hypertension because of insufficient certainty about feasibility and limits of normal.
Doppler echocardiography pulmonary hemodynamic measurements were performed at a progressively increased workload in 56 healthy male and 57 healthy female volunteers aged 19 to 63 years. Mean pulmonary artery pressure (mPAP) was estimated from the maximal tricuspid regurgitation jet velocity. Cardiac index was calculated from the left ventricular outflow velocity-time integral. Pulmonary vascular distensibility α index, the percentage change of vessel diameter per mm Hg of mPAP, was calculated from multipoint mPAP-cardiac output (CO) plots.
Peak exercise at 175 ± 50 W was associated with an mPAP of 33 ± 7 mm Hg and a CO of 18 ± 5 L/min. The slope of mPAP-CO relationships was 1.5 ± 0.5 mm Hg/L/min, and the distensibility coefficient (α) was 1.3% ± 1.0%/mm Hg. Maximal workload and cardiac index were higher in men than in women (P < .05), but mPAP-cardiac index relationships were not different. However, women had a higher α (1.6% ± 1.3%/mm Hg vs 1.1% ± 0.6%/mm Hg, P < .05). The average mPAP-cardiac index slope was higher and α lower in subjects ≥ 50 years old. Upper limits of normal of mPAP at exercise were 34 mm Hg at a CO < 10 L/min, 45 mm Hg at a CO < 20 L/min, and 52 mm Hg at a CO < 30 L/min. These values are in keeping with previously reported invasive measurements.
Exercise stress echocardiography of the pulmonary circulation is feasible and allows for flow-corrected definition of upper limits of normal. Women have a more distensible pulmonary circulation.