Supersensitive Response to Isoproterenol in Patients With Marked Global Reduction of Cardiac Metaiodobenzylguanidine Uptake

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It is unknown whether the non-transplanted, denervated human heart is supersensitive to β-adrenergic agonist in terms of inotropism and chronotropism. In the present study, 36 patients with normal left ventricular (LV) wall motion were divided into 3 groups according to the cardiac metaiodobenzylguanidine (MIBG) scintigrams: group I with normal MIBG uptake, group n with regionally reduced MIBG uptake, and group HI with globally reduced MIBG uptake (heart-to-mediastinum ratio <1.6). Before isoproterenol (IP) infusion, heart rate (HR), blood pressure (BP) and echocardiographic indices were similar among the groups. There was a trend toward a greater increase in HR with IP (O.Olμg・kg^<-1>・min^<-1>) in group IE (27±18beats/min) than in groups I (20±8) and II (17±8) despite the lack of a significant difference in BP reduction by IP. During IP infusion, increases in posterior wall motion amplitude and LV fractional shortening were significantly greater in group ffi (4.5±1.8 mm and 16.4±5.4%, respectively) than in groups I (1.5±2.5mm and 8.7±6.4%) and H (2.6±1.7mm and 8.9±7.9%). The present results suggest that the sympathetically denervated human heart is supersensitive to IP and the exaggerated responses may be caused, at least in part, by a postsynaptic mechanism. (Circ J 2003; 67: 745-749)
社団法人日本循環器学会の論文
2003-08-20