Background-The frequent provocation of ventricular tachycardia by stress or catecholamines and the efficacy of antiarrhythmic drugs with antiadrenergic properties suggest an involvement of the cardiac adrenergic system in arrhythmogenesis in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). Previous studies demonstrated abnormalities of the presynaptic uptake-1 assessed by I-123-MIBG-single-photon emission computed tomography. Methods and Results-This study investigated neuronal reuptake of norepinephrine (uptake-1) and beta-adrenergic receptor density in 8 patients with ARVC and 39 age-matched control subjects. All subjects underwent positron emission tomography with the volume of distribution (V-d) of [C-11]hydroxyephedrine (C-11-HED) used to assess presynaptic norepinephrine reuptake, the maximum binding capacity (B-max) of [C-11]CGP-12177 (C-11-CGP-12177) to assess postsynaptic beta-adrenergic receptor density, and [O-15]H2O for quantification of myocardial blood now. Patients with ARVC demonstrated a highly significant global reduction in postsynaptic beta-adrenergic receptor density compared with that in control subjects (B-max of C-11-CGP-12177: 5.9+/-1.3 vs 10.2+/-2.9 pmol/g tissue, P<0.0007), whereas the presynaptic uptake-1 tended toward reduction only (V-d of C-11-HED: 59.1+/-25.2 vs 71.0+/-18.8 mL/g tissue, NS). There were no differences in myocardial blood now between the groups, and plasma norepinephrine was within normal limits in patients and control subjects. Conclusions-The findings demonstrate a significant reduction of myocardial beta-adrenergic receptor density in patients with ARVC. This may result from a secondary downregulation after increased local synaptic norepinephrine levels caused by increased firing rates of the efferent neurons or as the result of impaired presynaptic catecholamine reuptake. These findings give new insights into the pathophysiology of arrhythmogenesis in ARVC, with potential impact on diagnostic evaluation and therapeutic management.
Abnormalities of cardiac sympathetic innervation in arrhythmogenic right ventricular cardiomyopathy - Quantitative assessment of presynaptic norepinephrine reuptake and postsynaptic beta-adrenergic receptor density with positron emission tomography
CAMICI , PAOLO
2000-01-01
Abstract
Background-The frequent provocation of ventricular tachycardia by stress or catecholamines and the efficacy of antiarrhythmic drugs with antiadrenergic properties suggest an involvement of the cardiac adrenergic system in arrhythmogenesis in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). Previous studies demonstrated abnormalities of the presynaptic uptake-1 assessed by I-123-MIBG-single-photon emission computed tomography. Methods and Results-This study investigated neuronal reuptake of norepinephrine (uptake-1) and beta-adrenergic receptor density in 8 patients with ARVC and 39 age-matched control subjects. All subjects underwent positron emission tomography with the volume of distribution (V-d) of [C-11]hydroxyephedrine (C-11-HED) used to assess presynaptic norepinephrine reuptake, the maximum binding capacity (B-max) of [C-11]CGP-12177 (C-11-CGP-12177) to assess postsynaptic beta-adrenergic receptor density, and [O-15]H2O for quantification of myocardial blood now. Patients with ARVC demonstrated a highly significant global reduction in postsynaptic beta-adrenergic receptor density compared with that in control subjects (B-max of C-11-CGP-12177: 5.9+/-1.3 vs 10.2+/-2.9 pmol/g tissue, P<0.0007), whereas the presynaptic uptake-1 tended toward reduction only (V-d of C-11-HED: 59.1+/-25.2 vs 71.0+/-18.8 mL/g tissue, NS). There were no differences in myocardial blood now between the groups, and plasma norepinephrine was within normal limits in patients and control subjects. Conclusions-The findings demonstrate a significant reduction of myocardial beta-adrenergic receptor density in patients with ARVC. This may result from a secondary downregulation after increased local synaptic norepinephrine levels caused by increased firing rates of the efferent neurons or as the result of impaired presynaptic catecholamine reuptake. These findings give new insights into the pathophysiology of arrhythmogenesis in ARVC, with potential impact on diagnostic evaluation and therapeutic management.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
