Letter by Schinkel et al 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”
To the Editor:
In a recent study by Blais and colleagues,1 the authors reported the use of dobutamine stress echocardiography (DSE) in patients with low-output, low-gradient aortic valve stenosis. Clinical decision making regarding these patients is challenging, and the clinical advantage of DSE is in distinguishing truly and pseudosevere aortic stenosis and evaluating contractile reserve.2–4 The authors have not made specific recommendations about the safety of DSE in these patients, but they have stated that “in a significant proportion of patients in this study (30%), the DSE had to be stopped before the maximal dose was reached because of the occurrence of symptoms, arrhythmias or hemodynamic abnormalities” (p 717). Review of the currently available data on DSE in patients with aortic stenosis shows that the high prevalence of side effects in the study of Blais et al1 is no exception. Pooled analysis of the 12 available studies demonstrates that in 30% (165 of 556) of patients with aortic stenosis, side effects occurred during dobutamine infusion. The highest prevalence of side effects was reported in studies that used a high-dose dobutamine protocol (up to 40 μg/kg per minute in some protocols with addition of atropine). Nevertheless, a subanalysis of the 7 studies that used a low-dose DSE protocol (up to 20 μg/kg per minute) demonstrates that in 17% (55 of 324) of patients, side effects occurred during dobutamine infusion.
The mechanism responsible for the high prevalence of side effects of DSE in patients with aortic stenosis is not clear. Dobutamine has positive inotropic and chronotropic effects, but it decreases peripheral vascular resistance. Patients with aortic stenosis have a fixed stroke volume, and adaptation to hemodynamic changes is impaired. Conceivably, these patients are more susceptible to symptomatic hypotension, whereas increased wall stress may cause subendocardial hypoperfusion, elicit ischemia, and serve as a substrate for arrhythmias.5
The high prevalence of side effects is a serious concern because patients with aortic stenosis and left ventricular dysfunction represent a high-risk group. Moreover, clinical information derived from a prematurely terminated DSE may be suboptimal because the increase in flow rate during a prematurely stopped test is limited. Because patients with aortic stenosis undergoing DSE are susceptible to potentially life-threatening side effects, it seems unwise to perform DSE when results are not likely to influence clinical management. In our center, we avoid high-dose DSE in patients with aortic stenosis, and we perform low-dose dobutamine infusion in these patients only under close monitoring.
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.
Monin JL, Quere JP, Monchi M, Petit H, Baleynaud S, Chauvel C, Pop C, Ohlmann P, Lelguen C, Dehant P, Tribouilloy C, Gueret P. Low-gradient aortic stenosis: operative risk stratification and predictors for long-term outcome: a multicenter study using dobutamine stress hemodynamics. Circulation. 2003; 108: 319–324.