Dobutamine Stress Echocardiography for the Assessment of Pressure-Flow Relationships of the Pulmonary Circulation

BACKGROUND: Stress testing of the pulmonary circulation (via increasing pulmonary blood flow) can reveal abnormal mean pulmonary artery pressure-cardiac output (mPpa-Q) responses, which may facilitate early diagnosis of pulmonary vascular disease. We investigated the application of dobutamine stress echocardiography (DSE) for the noninvasive assessment of mPpa-Q relationships. METHODS: DSE using an incremental dose protocol (<= 20 mu g/kg/min) was performed in 38 subjects (16 patients with pulmonary arterial hypertension [PAH] and 22 healthy control subjects). An additional 22 healthy control subjects underwent exercise stress echocardiography as a comparator group. Multipoint mPpa-Q plots were analyzed, and the pulmonary vascular distensibility coefficient a was calculated. RESULTS: DSE was feasible and informative in 93% of subjects. The average dobutamine-induced mPpa-Q slope was 1.1 +/- 0.7 mm Hg/L/min in healthy control subjects and 5.1 +/- 2.5 mm Hg/L/min in patients with PAH (P < .001). Th e dobutamine-induced a was markedly reduced in patients with PAH (0.003 +/- 0.001 mm Hg vs 0.02 +/- 0.01 mm Hg in control subjects, P < .001). When exercise and dobutamine stress were compared in healthy control subjects, the exercise-induced mPpa-Q slope was modestly higher (1.6 +/- 0.7 mm Hg/L/min, P = .03 vs dobutamine). In patients with PAH, lower functional class status was associated with lower dobutamine-induced mPpa-Q slopes (P = .014), but not with resting total pulmonary vascular resistance. CONCLUSIONS: Noninvasive assessment of mPpa-Q relationships is feasible with dobutamine stress. DSE may potentially be a useful noninvasive technique for stress testing of the pulmonary vasculature.