Response to Letter Regarding Article, “Projected Valve Area at Normal Flow Rate Improves the Assessment of Stenosis Severity in Patients With Low-Flow, Low-Gradient Aortic Stenosis: The Multicenter TOPAS (Truly or Pseudo-Severe Aortic Stenosis) Study”
We thank Dr Schinkel and colleagues for their comments, with which we are basically in agreement. Indeed, dobutamine stress echocardiography (DSE) in patients with low-flow, low-gradient aortic stenosis (AS) is a serious diagnostic procedure with potential complications. Thus, it should be limited to patients in whom it is likely to influence clinical management.
In this context, it should be remembered that the main objective of DSE is to increase transvalvular flow rate, without inducing myocardial ischemia, to (1) distinguish truly severe AS from pseudosevere AS and (2) assess myocardial contractile reserve. Hence, we agree that a low-dose protocol (ie, up to 20 μg/kg per minute) should be used, as was done in our study.1 In addition, we also prefer longer dobutamine stages (8 minutes instead of the 3 to 5 minutes previously proposed in the literature) to ensure that the patient is in a steady-state condition during Doppler-echo data acquisition and before proceeding to the next stage. The increase in heart rate should also be taken into consideration because it may predispose patients to myocardial ischemia and, at one point, it may override the inotropic effect, thereby limiting the increase in transvalvular flow.
Side effects occurred in 30% of our patients, but these side effects were minor and had no serious clinical consequence. Nonetheless, the point made by Schinkel and colleagues that the occurrence of these side effects may result in premature termination of the test and thereby decrease the diagnostic accuracy of DSE is well taken. However, this disadvantage may be partially or totally counterbalanced by the use of the projected effective orifice area at a normal flow rate, as was demonstrated in our study.
In conclusion, a low-dose gradual DSE protocol with careful monitoring and rigorous end points is safe and may provide important information for clinical decision making and risk stratification in patients with low-flow, low-gradient AS.
Blais C, Burwash IG, Mundigler G, Dumesnil JG, Loho N, Rader F, Baumgartner H, Beanlands RS, Chayer B, Kadem L, Garcia D, Durand LG, Pibarot P. Projected valve area at normal flow rate improves the assessment of stenosis severity in patients with low-flow, low-gradient aortic stenosis: the multicenter TOPAS (Truly or Pseudo-Severe Aortic Stenosis) study. Circulation. 2006; 113: 711–721.