Is the standard weight-based dosing of dobutamine for stress testing appropriate for patients of widely varying body mass index?

Background: Although a gradual increase in heart rate (HR) during dobutamine stress testing (DST) is desired, few data exists regarding whether this is similarly achieved in patients of widely varying body mass index (BMI). Whether difference in BMI contributes to variation in the hemodynamic and symptomatic response to dobutamine is also unknown. Methods: From prospectively acquired data of 2776 consecutive patients who underwent DST according to standard weight-based clinical protocol, we classified patients into 4 groups of BMI (kg/m²): <25 (normal), 25 to 29.9 (overweight), 30 to 39.9 (obese), and ≥40 (severely obese) and compared the rate of increase of HR, mean blood pressure, and development of symptoms for the groups. Results: Age was 68±12 years, 52% were men, BMI was 29.8 ± 6.6 kg/m² (range 14.5-81.4), 198 (7%) had BMI ≥40, and target HR was achieved in 2433 (88%). The rate of increase in HR was similar for each group of BMI after adjustment for age, gender, baseline HR, negative chronotropic use, and atropine administration. The percentage of patients in each group who achieved target HR was similar and the percentage of target HR achieved at each stage of dobutamine was essentially equivalent. Blood pressure responses and development of symptoms were similar in the 4 groups of BMI. Independent predictors of failure to achieve target HR included age, diabetes mellitus, treatment with negative chronotropic medications, and baseline HR; BMI was not a predictor (odds ratio [OR] 0.98, P = .086). Conclusion: The current weightbased protocol of dobutamine dosing for DST results in similar increases in HR and blood pressure for patients of widely varying BMI.