Cardiac positron emission tomography imaging with [C-11]hydroxyephedrine, a specific tracer for sympathetic nerve endings, and its functional correlates in congestive heart failure

The integrative mechanisms of autonomic dysfunction in congestive heart fai lure (CHF) remain poorly understood. We sought to study cardiac retention o f [C-11]hydroxyephedrine (HED), a specific tracer for sympathetic presynapt ic innervation, and its functional correlates in CHF. Thirty patients with mild to moderate heart failure underwent resting cardiac HED positron emiss ion tomography imaging, spectrum analysis testing of systolic pressure and heart rate variability in the resting supine and 70 degrees head-up tilt po sitions, and testing of baroreflex sensitivity. Compared with control subje cts, global myocardial HED retention index was reduced by 30% (p <0.01) in patients with CHF. The HED retention index did not correlate significantly with heart rate variability. However, it correlated with baroreflex sensiti vity at rest (r = 0.43, p = 0.05) and with systolic pressure low-frequency (0.03 to 0.15 Hz) variability at head up tilt (r = 0.76, p <0.01), as well as with low-frequency systolic pressure variability response from baseline to tilt (r = 0.75, p <0.01). We conclude that cardiac HED retention is redu ced in patients with CHF. This correlates with blunted vascular sympathetic effector responses during posture-induced reflex activation and baroreflex control of heart rate, suggesting an interdependence between cardiac presy naptic innervation abnormalities and neural mechanisms important to blood p ressure maintenance in CHF. (C) 1999 by Excerpta Medica, Inc.