EFFECTS OF DOBUTAMINE ON DOPPLER-ECHOCARDIOGRAPHIC INDEXES OF AORTIC-STENOSIS

Objectives. This study sought to assess the diagnostic implications of the flow dependence of Doppler echocardiographic indexes of aortic va lve stenosis. Background. Although valve area has been shown to change with alterations in flow rate, the diagnostic consequences of this ph enomenon remain unknown. Valve resistance has been suggested as a more stable index for evaluating aortic stenosis. Methods. A low dose dobu tamine protocol was performed in 35 patients with aortic stenosis. Hem odynamic indexes were obtained by Doppler echocardiography at baseline and at each dobutamine dose. Results. As a result of the shortening o f the systolic ejection period, flow increased from (mean +/- SD) 164 +/- 48 to 229 +/- 102 ml/s (p < 0.0001). At peak flow, valve area incr eased by 28% (from 0.5 +/- 0.2 to 0.6 +/- 0.3 cm(2), p < 0.0001), wher eas valve resistance decreased by 4% (from 498 +/- 252 to 459 +/- 222 dynes . s . cm(-5), p = 0.04). This observed change in resistance was smaller than that for valve area (p < 0.01). The flow dependence of va lve area varied among individual patients (p < 0.0001). Multivariate a nalysis identified calcific degenerative etiology (beta 0.29, p = 0.00 2), left ventricular velocity of fiber shortening (beta 0.22, p = 0.01 ), baseline flow (beta -0.28, p = 0.04) and amount of flow increase in duced by dobutamine (beta 0.90, p < 0.0001) as factors related to valv e area flow dependence. Conclusions. Although all Doppler echocardiogr aphic indexes of aortic stenosis are affected by flow, valve resistanc e is more stable than valve area under dobutamine-induced hemodynamic changes. Baseline valve area may be unreliable in patients with calcif ic degenerative aortic stenosis and low output states.