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 valve stenosis. BACKGROUND: Although valve area has been shown to change with alterations in flow rate, the diagnostic consequences of this phenomenon remain unknown. Valve resistance has been suggested as a more stable index for evaluating aortic stenosis. METHODS: A low dose dobutamine protocol was performed in 35 patients with aortic stenosis. Hemodynamic indexes were obtained by Doppler echocardiography at baseline and at each dobutamine dose. RESULTS: As a result of the shortening of the systolic ejection period, flow increased from (mean +/- SD) 164 +/- 48 to 229 +/- 102 ml/s (p < 0.0001). At peak flow, valve area increased by 28% (from 0.5 +/- 0.2 to 0.6 +/- 0.3 cm2, p < 0.0001), whereas 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 valve area varied among individual patients (p < 0.0001). Multivariate analysis identified calcific degenerative etiology (beta 0.29, p = 0.002), left ventricular velocity of fiber shortening (beta 0.22, p = 0.01), baseline flow (beta -0.28, p = 0.04) and amount of flow increased induced by dobutamine (beta 0.90, p < 0.0001) as factors related to valve area flow dependence. CONCLUSIONS: Although all Doppler echocardiographic indexes of aortic stenosis are affected by flow, valve resistance is more stable than valve area under dobutamine-induced hemodynamic changes. Baseline valve area may be unreliable in patients with calcific degenerative aortic stenosis and low output states.