Myocardial Infarction After Dog Bite
To the Editor:
I read with interest the report by Scharf et al1 of a 36-year-old man with an acute myocardial infarction presenting 2 days after a dog bite that was associated with leucocytosis and elevated C-reactive protein (CRP). Although I agree with the authors that infection and bacteremia may precipitate an acute myocardial infarction,2 I disagree with their statement that “it usually results from hypotension or from endocarditis with septic emboli to the coronary arteries.” None of my patients with pharyngitis and consequent acute myocardial infarction had hypotension or evidence of endocarditis, and those catheterized had normal or minor coronary artery disease.2
Inflammation, both local and systemic, plays a role in plaque vulnerability. Inflammation at the systemic level leads to elevated CRP and amyloid A levels and to activation of monocytes and adhesion molecules,3 4 all of which have been associated with acute coronary syndromes. Thus, the inflammatory response to the dog bite and the elevated CRP and leucocytosis, among other factors, led to endothelial dysfunction and changes in circulating clotting factors such as fibrinogen, which led to an increased clotting tendency and thrombotic coronary occlusion.5 Because no intravascular ultrasound was done, a minor atheroma instability or small plaque rupture associated with the inflammatory response cannot be excluded.
- Copyright © 2001 by American Heart Association
Differentiation between myocarditis and infarction cannot be made easily, and the gold standard for a positive diagnosis of myopericarditis would be a myocardial biopsy, which was not available in our patient. We still favor the diagnosis of myocardial infarction for the following reasons.
The picture of the patient’s nose, together with laboratory results of disseminated intravascular coagulation, are signs of microvascular thrombosis with cutaneous and systemic manifestations. The hemorrhagic skin lesions developed at the same time as the myocardial necrosis (ie, a few hours before admission). Therefore we assume that infectious-triggered disseminated intravascular coagulation caused microvascular thrombosis and myocardial infarction initially in the inferolateral region, with subsequent spread over more than one area supplied by the main 3 coronary arteries. The occlusion of multiple small coronary vessels explains the global hypokinesia and the normal coronary angiogram. Most importantly, several other cases illustrate acute myocardial infarction after dog bite. In one case, typical chest pain and ST elevation appeared 1 day before fever and systemic infection.R1 In another patient, acute coronary thrombosis was documented angiographically 3 weeks after dog bite. The patient had no signs of infection and was discharged after 10 days but had to be readmitted when blood cultures yielded Capnocytophaga canimorsus.R2
In conclusion, Capnocytophaga canimorsus sepsis can rarely present as a distinct clinical pattern with disseminated intravascular coagulation and widespread capillary thrombosis, similar to Waterhouse-Friderichsen syndrome or thrombotic thrombocytopenic purpura,R3 which can lead to extensive gangreneR4 and a mortality >30%.R5 Clinical diagnosis before time-consuming microbiological isolation is mandatory to insure early antibiotic treatment. The old Roman mosaic in the “House of the Tragic Poet” in the ruins of Pompeii with the engraved Latin comment cave canem (beware of dog) and our images should be kept in mind when taking care of patients with signs of acute myocardial infarction after animal bites.
Ehrbar HU, Gubler J, Harbarth S, et al. Capnocytophaga canimorsus sepsis complicated by myocardial infarction in two patients with normal coronary arteries. Clin Infect Dis. 1996;23:335–336.
Newton NL, Sharma B. Acute myocardial infarction associated with DF-2 bacteremia after a dog bite. Am J Med Sci. 1986;291:352–354.
Pers C, Gahrn HB, Frederiksen W. Capnocytophaga canimorsus septicemia in Denmark, 1982–1995: review of 39 cases. Clin Infect Dis. 1996;23:71–75.