By definition the Beta-blockers are substances which antagonize in a specific, competitive and reversible manner the action of the endogenous or exogenous catecholamines in the beta adrenergic receptors.
They are found in the smooth muscle (vascular and bronchial) causing dilatation and relaxation of these structures, and a considerable number is also found in the cardiac muscle exerting positive inotropic and chronotropic influence. The beta receptors are distributed in the heart leading to an increase of the inotropism and chronotropism. The early administration of atropine optimized the hemodynamic response, reduced test time in patients with or without Beta-blockers and reduced the number of inconclusive tests in the early protocol. The chronotropic response during dobutamine stress echocardiography was significantly reduced with the use of Beta-blockers. Complications were similar in both groups. The patients with Beta-blockers in Group A&B had a lower rate of inconclusive tests (26%) compared to those in Group C (40%). The same findings occurred in the standard protocol (Group C), however the early administration of atropine reduced test time both in the presence and absence of this therapy (p = 0.0001). Resultsīeta-blocked patients who received early atropine (Group A&B) had a significantly lower double product (p = 0.008), a higher mean test time (p = 0.010) and required a higher dose of atropine (p = 0.0005) when compared to the patients in this group who were not Beta-blocked. Analysis of the effects of Beta-blockers was done regarding the behavior pattern of heart rate and blood pressure, test time, number of conclusive and inconclusive (negative sub-maximum test) results, total doses of atropine and dobutamine, and general complications.
The administration of atropine was randomized into two groups: A or B (early protocol when atropine was administered at 10 and 20 mcg/kg/min of dobutamine, respectively) and C (standard protocol with atropine at 40 mcg/kg/min of dobutamine). One hundred and twenty-one patients were submitted to dobutamine stress echocardiography for the investigation of myocardial ischemia. To study the effects of Beta-blockers during Dobutamine Stress Echocardiography (DSE) comparing the hemodynamic benefits of an early administration of atropine in patients taking or not Beta-blockers.
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