REGIONAL DISTRIBUTION AND KINETICS OF [F-18] 6-FLURODOPAMINE AS A MEASURE OF CARDIAC SYMPATHETIC ACTIVITY IN HUMANS

Objectives-To determine whether an increase in cardiac sympathetic act ivity produced by exercise or sublingual glyceryl trinitrate causes an increased rate of loss of fluorine-18 from the myocardium after intra venous [F-18]6-fluorodopamine ([F-18]F-DA) in normal volunteers. In ad dition, to determine the contribution of non-specific uptake of [F-18] F-DA in the myocardium in patients with recent heart transplant. Proto col-[F-18]F was prepared by direct electrophilic fluorination of dopam ine. Nine healthy volunteers each received 1.85 x 10(8) Bq (168-250 mu g) [F-18]F-DA over a period of 3 min and were scanned for 2 h in an E CAT 953/31 tomograph. Three controls were scanned before and after vig orous cycle exercise and two were scanned before and after sublingual glyceryl trinitrate. In addition, two patients (1 and 2 years post-hea rt transplant) underwent a myocardial perfusion study with ammonia lab elled with nitrogen-13 followed by an [F-18]F-DA study. Results-There was intense uniform uptake of [F-18]F-DA throughout the myocardium in the healthy volunteers. The time course of F-18 in the myocardium unde r resting conditions fitted a biexponential function with mean half-ti mes of 8.0 and 109 min. Vigorous exercise produced a three to fivefold increase in the rate of loss of F-18 compared with that when resting. After glyceryl trinitrate, one control had a profound reduction in bl ood pressure (23%) and twofold increase in the rate of loss of myocard ial F-18, The other control had no physiologically significant change in blood pressure, heart rate, or rate of loss of myocardial F-18, Upt ake of [F-18]F-DA in the two posttransplant patients was confined to a small anterobasal region adjacent to the atrioventricular groove, whi le blood flow, as measured with [N-13] ammonia, was uniformly distribu ted throughout the myocardium. Partial reinnervation of the myocardium was confirmed by the presence of distinct low frequency spectral peak s of the heart rate power spectrum in both patients. Conclusions-These results suggest that the uptake of [F-18]F-DA reflects the distributi on of cardiac sympathetic innervation and that the rate of loss of F-1 8 from the myocardium partially reflects spill over of noradrenaline. The technique may be useful in investigating various cardiac condition s in which the sympathetic system is compromised.