[Hypokinetic arrhythmia, paradoxical chronotropic reaction and hypotension during dobutamine stress test].

The aim of this study was to evaluate the incidence of hypokinetic arrhythmias, bradycardiac (BR) and hypotensive reactions in a population of 775 patients during dobutamine stress test (DST): 281 patients (36.2%, group I) were symptomatic for thoracic pain without any history of coronary artery disease (CAD); 494 patients (63.8%, group II) were evaluated 3-4 weeks after an acute myocardial infarction (AMI) to stratify ischemic risk. None of these patients was receiving coronarodilating therapy.DST was performed using an infusion of 5, 10, 20, 40 micrograms/kg/min for 5 minutes during the first two stages and for 3 minutes during subsequent stages, and was accompanied by EKG and echocardiographic monitoring. BR was defined as severe when heart rate diminished more than 40 b/min, moderate when the decrease ranged between 20 and 39 b/min, and mild when the decrease was less than 20 b/min.A total of 34 (4.38%) BR were observed, 19 (55%) in group I and 15 (45%) in group II. BR were severe in 12 patients (35.9%), 3 with recent AMI (2 inferior and 1 anterior) and 9 without a history of CAD. Fifteen (45%) presented moderate BR, 8 with recent AMI (6 inferior and 2 anterior); 7 cases were in group I. Mild BR was observed in 7 patients (20%), 2 with recent AMI (1 inferior, 1 anterior), of which 5 were in group I. Episodes of junctional rhythm were also observed in 10 patients (29.4%) and 1 patient (2.9%) presented 2nd degree AV block during DST positive for ischemia. The mean duration of bradycardic episodes was 89.6 seconds (+/- 29.8) and only 3 patients (8.8%) presented significant hypotension. In 13 patients (38.2%) arrhythmia was observed during dobutamine-induced ischemia. In spite of the often severely diminished heart rate, no significant hypotension was evident during the bradycardiac episode in 19 patients (55%). Only one patient (2.9%) showed a decrease of more than 40 mmHg.In conclusion, we found that the incidence of BR during DST (4.38%) is higher than that reported in the literature; moreover, patients with recent inferior AMI showed a higher incidence of BR compared to patients with AMI in other sites (9 vs 4, p = n.s.). We feel that ischemia alone may not be responsible for hypokinetic arrhythmia during DST, but that dobutamine-induced neurovegetative reflexes may also contribute to the pathophysiological mechanisms underlying the phenomenon.