[Mitral valve prolapse: a factor exacerbating peranesthetic anaphylactic shock].

Initial cardiac failure in anaphylactoid shock is rare, classically related to cardiac anaphylaxis occurring in a highly sensitized patient. However, this anaphylaxis is not always found; the case described here of a histamine shock with ventricular fibrillation after the injection of thiopentone is a good example of this. The severity of the shock may be explained by the presence of a prolapse of the small flap of the mitral valve.