To determine the evolution with age, of extrinsic and intrinsic sinus node electrophysiological parameters and to assess the role of each component of the autonomic nervous system relative to age in patients with and without sick sinus syndrome, electrophysiological studies of sinus node function were performed in 223 patients subdivided into four groups according to the results of their electrophysiological testings: group I included patients with normal extrinsic and intrinsic sinus node function, group II patients with exclusive extrinsic sinus dysfunction, group III patients with exclusive intrinsic sinus dysfunction and group IV patients with extrinsic and intrinsic sinus node dysfunction. The electrophysiological study was performed twice: at basal state and after autonomic blockade. Whatever the sinus node function (normal or abnormal) the extrinsic sinus node electrophysiological variables did not correlate with age; inversely all the electrophysiological measurements of the intrinsic sinus node (normal or abnormal) lengthened progressively with age, suggesting an ageing phenomenon of the intrinsic sinus node throughout life. Moreover, the study of the percentage of chronotropy of the sinus node electrophysiological variables shows a predominance of vagal tone in young subjects, whereas sympathetic activity is most prominent in elderly patients with and without sick sinus syndrome. The sinus node (normal or pathological) represents an equilibrated system: the age-related modification of the autonomic nervous system counterbalances the senescence of the intrinsic sinus node in such a way that the basal electrophysiological characteristics remain stable throughout life.

Physical activity during leisure time and on the job have been measured with standardized interview techniques in 1,513 normal men, aged 40-55 years, who were regularly employed in different industries. Physical fitness was simultaneously estimated by measuring the work load at which a heart rate of 150 bpm was reached on a standardized exercise test. The median energy expenditure from leisure time activities above the basal metabolic rate was 195 kcal/day; 19% of these activities were classified as heavy, 37% as moderate and 43% as light intensity. The median energy expenditure from job physical activity was 1,676 kcal/day including basal metabolic rate. The median physical fitness level was 125 W. The leisure time activity score was significantly related to physical fitness through the light and the heavy intensity subscores. Independently, job physical activity was also significantly related to physical fitness. However, both activity scores accounted for only 2% of the variance in physical fitness. The data illustrate an overall low energy expenditure profile of middle-aged normal men and a low order relationship between physical activity pattern and physical fitness.

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Our data suggest that myocardial bridging possibly enhanced by catecholamines during stress may contribute, in association with left ventricular hypertrophy, to the preferential apical localization of the apical ballooning syndrome. Further investigations are necessary to confirm