Reactivity of isolated human right atria to norepinephrine in various disease states

The reactivity of isolated, electrically driven, right human atrial muscle to norepinephrine was studied in patients with coronary heart disease, with and without proximal right coronary artery occlusion, and in patients with mitral valve disease. The dose-effect curves for norepinephrine and ED50 doses for each group were compared. We found no difference in reactivity of atria from both coronary artery disease groups. The mitral valve disease group dose-effect curve was shifted to the right (potency ratio 3.98), and the maximal effect was significantly higher than in both coronary artery disease groups. We suggest that adrenoreceptor down regulation could account for observed ED50 difference. The difference in maximal responses could depend on more effective contraction mechanism in mitral valve disease myocardium. We conclude that occlusion of proximal right coronary artery does not necessarily mean ischaemia of right atrium and/or ischaemia does not change myocardium reactivity to norepinephrine.