Paradoxical sinus deceleration has been described during dobutamine stress echocardiography. Usually the heart rate increases progressively with increasing dose of dobutamine infusion used for stress echocardiography. A paradoxical decrease in heart rate in some individuals during high dose dobutamine infusion has been called paradoxical sinus deceleration. One study found an 8% incidence of paraxoxical sinus deceleration during dobutamine stress echocardiography (Attenhofer CH et al, JACC, 1997;29:994-999). This study found that though it is often associated with coronary artery disease (CAD), it can also occur in those without significant CAD. It was not specifically associated with disease of right coronary artery disease.
This cadioinhibitory response may be a manifestation of the Bezold-Jarish reflex. Bezold-Jarish reflex inhibits sympathetic activity (sympathetic withdrawl) and increases parasympathetic activity, resulting in bradycardia, which may be associated with vasodilatation, nausea and hypotension. Bezold-Jarish has been described in the setting of inferior wall infarction and coronary angiography. Original description of Bezold Jarish-reflex was of experimentally induced bradycardia with injection of veratrum alkaloids.
Paradoxical sinus deceleration may cause underdetection of coronary artery disease due to the lower heart rates achieved. In those without evidence of myocardial ischemia, atropine is useful to counter the deceleration as well as to improve the chance of detection of an ischemic response.