Effects of different left ventricular load conditions on myocardial beta-adrenoceptor density in patients with rheumatic heart valvular disease

Assessment of the Effects of Age, Gender, and Exercise Training on the Cardiac Sympathetic Nervous System Using Positron Emission Tomography Imaging

BACKGROUND

Using positron emission tomography (PET) imaging, we sought to determine whether normal age or exercise training cause changes in the cardiac sympathetic nervous system function in male or female healthy volunteers.

METHODS

Healthy sedentary participants underwent PET studies before and after 6 months of supervised exercise training. Presynaptic uptake by the norepinephrine transporter-1 function was measured using PET imaging of [(11)C]-meta-hydroxyephedrine, a norepinephrine analog, and expressed as a permeability-surface area product (PSnt in mL/min/mL). Postsynaptic function was measured as β-adrenergic receptor density (β'max in pmol/mL tissue) by imaging the β-receptor antagonist [(11)C]-CGP12177. Myocardial blood flow (MBF in mL/min/mL tissue) was measured by imaging [(15)O]-water.

RESULTS

At baseline, there was no age difference in β'max or MBF but PSnt declined with age (1.12±0.11 young vs 0.87±0.06 old, p = .036). Before training, women had significantly greater MBF (0.87±0.03 vs 0.69±0.03, p < .0001) and PSnt (1.14±0.08 vs 0.75±0.07, p < .001) than men. Training increased VO2 max by 13% (p < .0001), but there were no training effects on β'max, PSnt, or MBF. Greater MBF in females and a trend to increased PSnt post-training persisted.

CONCLUSION

With age, presynaptic uptake as measured by PSnt declines, but there were no differences in β'max. Endurance training significantly increased VO2 max but did not cause any changes in the measures of cardiac sympathetic nervous system function. These findings suggest that significant changes do not occur or that current PET imaging methods may be inadequate to measure small serial differences in a highly reproducible manner.

Heart rate variability in children with acute rheumatic fever

OBJECTIVE

Acute rheumatic fever is a systemic inflammatory disease occurring after acute streptococcal tonsillopharyngitis. The PR prolongation in these patients is thought to be due to increased vagal activity. There has been no previous study investigating the autonomic balance in patients with acute rheumatic fever. In this study, we aimed to investigate the balance of the autonomic nervous system in children with acute rheumatic fever by analysis of heart rate variability.

METHODS

We evaluated the heart rate variability parameters in 50 patients with acute rheumatic fever and 37 comparable control subjects. Both groups underwent 24-hour electrocardiography monitoring, and time- and frequency-domain heart rate variability parameters were calculated. A total of 39 patients (78%), with (n = 28) or without (n = 11) other major findings, had carditis, and the remaining 11 (22%) did not. The PR interval was found to be prolonged in 10 (20%) of the patients at the beginning.

RESULTS

In the study group, the time- and frequency-domain heart rate variability parameters showed a sympathetic dominance compared with the control group, with a p-value less than 0.05. When compared with the control group, the time- and frequency-domain heart rate variability parameters showed a significant sympathetic dominance in patients with both prolonged PR and normal PR intervals in the acute period, with a p-value less than 0.05. When compared with patients with normal PR interval, mean normalised low frequency and normalised high frequency parameters suggested a relatively lower sympathetic dominance in patients with prolonged PR interval, with a p-value less than 0.05.

CONCLUSION

Our results indicated that in the acute period of rheumatic fever, sympathetic dominance is apparent; in patients with prolonged PR interval, sympathetic dominance is relatively lower when compared with the patients with normal PR interval.