[Electrocardiographic study of sinus bradycardia associated with enterohemorrhagic Escherichia coli O157: H7 infection].

A severe outbreak of hemorrhagic colitis occurred at a kindergarten in Saitama, Japan in October, 1990. Children who were affected by enterohemorrhagic E. coli O157: H7 infection showed apparent bradycardia as well as severe bloody diarrhea, generalized convulsion, or hemolytic uremic syndrome. Cardiac involvement such as bradycardia observed in the patients of this outbreak has not been described in previous reports about EHEC infection, while bradycardia has been well known in typhoid fever due to salmonella typhosa infection. Electrocardiographic examination was performed to evaluate bardicardia, utilizing electrocardiography at rest and Holter's twenty-four hour electrocardiography. In the report, we demonstrate that the bradicardia was due to reduced frequency of sinus node. Both average heart rate and average minimum heart rate of the patients at night (74.0 +/- 5.6 BPM and 57.0 +/- 5.1 BPM, respectively) decreased significantly, as compared with controls (84.6 +/- 9.3 BPM and 66.3 +/- 8.0 BPM respectively) (p < 0.01). CVRR of the patients (0.120 +/- 0.019, respectively) increased significantly as compared with controls (0.090 +/- 0.010, respectively). These results indicate that an activated parasympathetic nervous system, that is, activation of the vagal nerve, might have induced the sinus bradycardia observed in the patients with EHEC infection.