REACTIVITY OF ISOLATED HUMAN RIGHT ATRIA TO NOREPINEPHRINE IN VARIOUSDISEASE STATES

The reactivity of isolated, electrically driven, right human atrial mu scle to norepinephrine was studied in patients with coronary heart dis ease, with and without proximal right coronary artery occlusion, and i n patients with mitral valve disease. The dose-effect curves for norep inephrine and ED(50) doses for each group were compared. We found no d ifference in reactivity of atria from both coronary artery disease gro ups. The mitral valve disease group dose-effect curve was shifted to t he right (potency ratio 3.98), and the maximal effect was significantl y higher than in both coronary artery disease groups. We suggest that adrenoreceptor down regulation could account for observed ED(50) diffe rence. The difference in maximal responses could depend on more effect ive contraction mechanism in mitral valve disease myocardium. We concl ude that occlusion of proximal right coronary artery does not necessar ily mean ischaemia of right atrium and/or ischaemia does not change my ocardium reactivity to norepinephrine.