Paradoxical Sinus Deceleration

Paradoxical Sinus Deceleration

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 paradoxical sinus deceleration during dobutamine stress echocardiography [1]. ThAs study found, though it is often associated with coronary artery disease, it can also occur in those without significant CAD. It was not specifically associated with disease of right coronary artery.

This cardioinhibitory response may be a manifestation of the Bezold-Jarisch reflex. Bezold-Jarisch reflex inhibits sympathetic activity and increases parasympathetic activity, resulting in bradycardia, which may be associated with vasodilatation, nausea and hypotension. Bezold-Jarisch reflex has been described in the setting of inferior wall infarction and coronary angiography. Original description of Bezold-Jarisch reflex was of experimentally induced bradycardia with injection of veratrum alkaloids.

Paradoxical sinus deceleration may cause under detection 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.

Reference

1. Attenhofer CH, Pellikka PA, McCully RB, Roger VL, Seward JB. Paradoxical sinus deceleration during dobutamine stress echocardiography: description and angiographic correlation. J Am Coll Cardiol. 1997 Apr;29(5):994-9.