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 increase 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.
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This study was presented in part at the 68th Scientific Sessions of the American Heart Association, Anaheim, California, November 1995 and at the XVIIth Congress of the European Society of Cardiology, Amsterdam, The Netherlands, August 1995.
