Combined low dose dobutamine and exercise stress echocardiography: a new hybrid protocol to detect inducible ischaemia

Myocardial response to stress echocardiography may be elicited physiologically, through exercise, or pharmacologically, often with dobutamine. Both have advantages but also limitations due to reduced exercise capacity or side-effects to stressor agent/lack of closeness to true pathophysiology of ischaemic cascade. We have combined low-dose dobutamine and exercise, creating a “hybrid” protocol to utilise the advantages of both techniques and limit the drawbacks. The aim of the study was to evaluate its safety and feasibility. In the hybrid protocol low dose dobutamine infusion (up to 10 mcg/kg/min) is enhanced by supine bicycle exercise at 3 min increments of workload of 25W to achieve target heart rate. We analysed safety and outcome data for all patients who underwent this protocol from 2017-2022. 727/835 (87.1%) patients referred for evaluation of ischaemia underwent the hybrid protocol. The median age was 61 years old and 61% (442/727) were men. The median exercise time was 11 (9-13.5) minutes with a median maximum workload of 100W (75-125). 670/727 (92.2%) achieved target heart rate. Atropine was not used. 192/727 (26.4%) of studies were positive for ischaemia. 102/122 (83.6%) with positive stress who underwent invasive angiography had significant coronary disease. The incidence of complications was low: 1/727 - severe arrhythmia, 5/727 (0.7%) developed a vasovagal episode and 14/727 (1.9%) had a hypertensive response to exercise. Our findings suggest that this protocol is safe, feasible and has a high success rate in achieving target heart rate.