What causes bradycardia in individuals with anaphylaxis?

Updated: May 16, 2018
  • Author: S Shahzad Mustafa, MD; Chief Editor: Michael A Kaliner, MD  more...
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Conduction defects and sympatholytic medications may also produce bradycardia. Excessive venous pooling with decreased venous return (also seen in vasodepressor reactions) may activate tension-sensitive sensory receptors in the inferoposterior portions of the left ventricle, thus resulting in a cardio-inhibitory (Bezold-Jarisch) reflex that stimulates the vagus nerve and causes bradycardia.

The implications of relative or absolute bradycardia in human anaphylaxis and hypovolemic shock have not been studied.

However, one retrospective review of approximately 11,000 trauma patients found that mortality was lower with the 29 percent of hypotensive patients who were bradycardic when they were compared to the group of hypotensive individuals who were tachycardic, after adjustment for other mortality factors. [7] Thus, bradycardia may have a specific compensatory role in these settings.

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