Physiological fluctuation of the human left ventricle sympathetic nervous system assessed by iodine-123-MIBG.

Abstract

It has been proposed that sympathetic nervous system pathophysiology is involved in the development of cardiovascular disorders. Since cardiac adrenergic activity has been difficult to assess in humans, physiological changes in the sympathetic nervous system in the human left ventricle remain unclear. To determine if age and gender influence the sympathetic nervous function of the left ventricle, 300 angiographically normal subjects (170 men, 130 women; age range 40-79 yr) had 123I-metaiodobenzylguanidine (MIBG) cardiac imaging. Regional quantitative analysis of MIBG uptake and washout rate was performed. Men and women had prominent age-related decreases in MIBG uptake in the inferior and lateral walls (r2 = 0.34, p <0.0001 for both). Both genders had a significant positive correlation between regional washout rate and age in each region. In contrast to men, women had strong positive correlations in all regions (r2 = 0.54, p <0.0001 in the anterior wall, r2 = 0.56, p <0.0001 in the lateral wall and r2 = 0.44, p <0.0001 in the inferior wall). According to the decade-by-decade analysis of washout rate, women had a significantly lower washout than men under 50 yr in every region and a significantly higher washout in the lateral wall than men over 70 yr. The sympathetic nervous system in the human left ventricle showed age- and gender-related regional changes. The findings suggested that men have high sympathetic nerve activity from a younger age, and women have a progressive increase in sympathetic nerve activity with aging. These changes may contribute to the age and gender differences in the incidence and development of cardiac disorders.