Haemodynamic changes during dobutamine stress echocardiography in patients with and without ischaemia

We studied haemodynamic changes during dobutamine stress echocardiography in 69 patients (mean age 58 years, 6 female, 63 male) referred for investigation of chest pain. We used a standard protocol of 3 min stages using infusion rates of 5, 10, 20, 30 and 40 μg/kg/min. Heart rate rose from 74 (13) to 123 (21) beats per min with the major increment occurring during the high dose phase of the study (>20 μg/kg/min). Stroke volume was calculated as the product of left ventricular outflow tract cross-sectional area and the velocity integral of the continuous wave aortic signal. Mean stroke volume increased from 67.5 (22) ml pre-test to 82 (22) ml at 20 μg/kg/min dose (P<0.0001) and 85 (21) ml at 40 μg/kg/min (P<0.00001). Only 15 patients (26%) reached their maximal stroke volume by 10 μg/kg/min, 38 patients (65%) reached maximal stroke volume by 20 μg/kg/min. Patients with ischaemic responses tended to have a blunted rise in stroke volume from 67 (22) ml to 85 (22) ml at maximum compared with a rise from 69 (23) to 92 (19) ml in those without ischaemia (P=0.09). In conclusion, the early rise in cardiac output during dobutamine stress was mainly due to a rise in stroke volume and the later rise due to an increase in heart rate. Individual increases in stroke volume did not adequately differentiate between ischaemic and non-ischaemic results.