HRH1 and myocardial ischemia: Because mast cellsaccumulate at sites of coronary atherosclerotic plaques and IgE antibodies bound tomast cells can trigger mast cell degranulation, some investigators have suggestedthat anaphylaxis may lead to myocardial ischemia by promoting plaque rupture[36,37].Stimulation of the H1 histamine receptor may also produce coronary arteryvasospasm[37,38].