Aims: Dobutamine stress echocardiography is a time-consuming test, often requiring atropine at the end of the protocol to achieve target heart rate (HR). We examined whether earlier administration of atropine in appropriate patients would shorten test time and increase the likelihood of achieving peak HR.
Methods: Two hundred and seventy consecutive patients were randomized prospectively to conventional or early atropine protocols. Of these, 120 patients with an inadequate HR response [mid-30 μg/kg/min HR<100 (age <50) or <90 (age >50); or mid-40 μg/kg/min stage HR<120 (age <50) or <110 (age >50)] were included in the analysis. The remaining patients were used in a model to define which patients are likely to require atropine.
Results: The 61 patients receiving early-atropine had decreased test-time relative to the 59 not receiving early-atropine (17:05 vs . 18:24 min:sec, P =0·014) accompanied by a 10% reduction in total dobutamine dose ( P =0·008). Their HR at end of 40 μg/kg/min was 123±18 vs . 105±17 respectively, P <0·0001. Only 7% of the early-atropine group failed to reach target HR vs . 15% not receiving early-atropine. By multivariate analysis, age ( P <0·0001), HR at end of 30 μg/kg/min stage ( P <0·0001), β-blocker use ( P =0·009) and baseline HR ( P =0·04) were predictors of need for atropine.
Conclusion: Giving atropine early in appropriate patients can reduce test times without an increase in side effects. Our model enables accurate prediction of these patients.