Blunted heart rate response during dobutamine stress echocardiography: Should atropine be administered earlier?

Atropine (AT) has been used at peak dobutamine infusion during dobutamine stress echocardiography (DSE) in pts who cannot achieve 85% maximal predicted heart rate (MPHR) at peak infusion. The purpose of this study was to determine whether the heart rate at end 20 mcg/kg/min (HR20) was predictive of the need for AT at peak dobutamine (DB). This protocol modification could potentially shorten study time. Review of 68 consecutive pts requiring AT at peak DB during DSE as well as 66 age- and sex-matched controls who achieved ≥85% MPHR and who did not require atropine was completed. Rest HR HR20 HR Peak Test Time (min) Controls 77 116 134 12 Atropine 67 85 134 18 p<.0001 Pts requiring AT were more often taking beta blockers (BB) (15% vs 44%; p<.001). HR20 was assessed to determine parameters where pts who would require AT at peak DB could be identified early. The number of pts in both groups who achieved each level of %MPHR at HR20 is depicted: %MPHR at HR20: <65 <60 <55 <50 Controls 12 (18%) 7 (10%) 5 (7%) 5 (7%) Atropine 53 (80%) 42 (64%) 32 (48%) 24 (36%) HR at 20 mcg/kg/min was predictive of a need for AT at peak DB; HR20 <55 %MPHR identified a group of pts who would likely require AT at peak DB. Total DB infusion time was significantly shorter in the control group (12 vs 18 min; p<.001). Administration of AT at the end of the 20 mcg/kg/min dose in pts with blunted HR response to DB may shorten study time and therefore minimize adverse side effects. Because atropine administration can result in a prolonged tachycardia, larger prospective studies are needed to test these parameters and define a protocol for AT administration.