Left ventricular outflow tract obstruction provoked during dobutamine stress echocardiography predicts future chest pain, syncope, and near syncope

Background Although dobutamine stress echocardiography (DSE) is associated with dynamic left ventricular (LV) obstruction, it is unknown whether such obstructive event, in general, and the specific site of obstruction, in particular, have unique clinical prognostic significance. We sought to determine whether dynamic LV outflow tract (LVOT) versus LV midcavitary obstruction provoked during DSE would predict future chest pain, syncope, and/or near syncope. Methods Two hundred thirty-seven patients (145 men and 92 women, mean age 58 +/- 13 [+/- SD] years) without DSE-provoked ischemia underwent continuous wave Doppler interrogation to detect any inducible dynamic flow obstruction. Patients were prospectively followed for a mean duration of 31 +/- 13 months. Results One hundred fifty-four of 237 patients had no provoked LV obstruction (group 1). Fifty-four (22.8%) had provoked LV midcavitary (group 2) obstruction, and 29 (12.2%) had outflow tract (group 3) obstruction. During follow-up, chest pain occurred more frequently in groups 2 (46%, P<.05) and 3 (52%, P=.05) as compared with group 1 (31%). A higher incidence of syncope and/or near syncope was noted in group 3 (21% vs 9% in group 1). LVOT obstruction but not midcavitary obstruction was a significant predictor of future chest pain (relative risk 2.63, P = .0021) and syncope and/or near syncope (relative risk 3.11, P = .036). Kaplan-Meier analysis showed a significantly less event-free survival (P = .025) for the combined end point of chest pain, syncope, and/or near syncope in patients with LVOT obstruction. Conclusions This is the first prospective study to identify the differential prognostic implications of the site of dynamic obstruction noted during DSE. Our results demonstrate that DSE-provoked LVOT obstruction is an independent positive predictor of future episodes of chest pain and syncope and/or near syncope. These findings warrant larger studies addressing treatment options to ameliorate symptoms in this subgroup of patients.