Stress Echocardiography

The correct answer is A


Explanation

Stress echocardiography has been developed in recent years as an effective noninvasive test for the detection and assessment of coronary artery disease. This method combines exercise with 2-dimensional echocardiography, which can assess regional and global left ventricular function during stress. Dobutamine infusion, a pharmacologic means of producing cardiovascular stress, appears to be an excellent alternative to exercise in echocardiographic studies. Currently, it is reserved for patients who cannot exercise at a meaningful level because of advanced age, physical deconditioning, or other factors.



Dobutamine infusion is the method used most often for pharmacologic stress echocardiography. Graded dobutamine infusion--10 to 40 micrograms/kg per minute in 3-minute stages--increases myocardial oxygen demand in a fashion similar to that of staged exercise. During the dobutamine infusion, it is apparent that heart rate, contractility, and blood pressure are increased. Dobutamine has the advantage of rapid onset of action, and its effects can be reversed by giving an intravenous beta-blocker. A synthetic catecholamine that has a relatively short half-life (about 2 minutes) , dobutamine has strong agonist activity at the beta1 receptor and mild agonist activity at the beta2 and alpha1 receptors.



Atropine sulfate can be used to increase heart rate, if necessary, and is usually administered at the peak dobutamine dose. It is usually given as a 0.5-mg bolus and in 0.25-mg increments every 60 seconds (maximum dose, 1-1.5 mg) until the desired heart rate is achieved.

Dobutamine infusion is stopped after images are acquired at peak heart rate--or sooner if the patient has tachyarrhythmias.

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