SUMMARY High salt intake accelerates hypertension in humans and increases cardiovascular morbidity and mortality. The temporal relation between blood pressure (BP) deration and appearance of vascular lesions during salt-loading was studied in the spontaneously hypertensive rat (SHR). Starting at 5 weeks of age, SHRs and normotensive Wistar-Kyoto rats (WKYs) were given 1% NaCl in their drinking water; SHRs and WKYs on tap water served as controls. Animals from each group were sacrificed at 10 and 20 weeks of age, and the aorta and Intrarenal vessels were studied by light and electron microscopy.Neither BP nor vascular morphology of WKYs were affected by 1% NaCl. In SHRs, the course of BP was not affected by the addition of salt for at least 11 weeks, but vascular changes were significantly aggravated within 5 weeks. Thus, aortic intimal lesions progressed more rapidly so that, by 20 weeks of age, 50% of the animals had 3+ lesions while, in control SHRs, they did not exceed the 2+ grade. Salt-loading resulted in significant thickening of the aortic media between the 10th and 20th week of age while control SHRs showed no increment within the same time interval. Also, small intrarenal arterial vessels of salt-treated SHRs had significantly narrower lumina and greater wall thickness at both 10 and 20 weeks of age. In addition, they showed intimal proliferations and necrotizing lesions which were absent from control SHRs at these ages.These results show that, in this experimental model, the aggravation of vascular changes is not merely a sequela of further elevation of BP. Since the adverse effect of salt on the vessels was not teen In WKYs, it is likely that this effect is related to genetic factors or to higher susceptibility of hypertensive vessels. The Aoki-Okamoto strain of spontaneously hypertensive rats (SHRs), a model of human essential hypertension, 5 offers the opportunity to study the pathogenesis of hypertensive vascular lesions. In these

The EXCEL VR, an accelerometer-based pacemaker (AC), and the Legend, a pacemaker utilizing a piezoelectric crystal (PZ), were compared under ergometric conditions and during stair climbing to assess the appropriateness of their rate responses. The pacemakers, programmed to the manufacturers' nominal settings in order to compare different technologically based sensors under identical conditions, were strapped over subjects' left mid-pectoral region. Placement of the devices was randomized to control for positional effects. Ten healthy subjects (55-72 years) completed a graded exercise treadmill test to 80% of maximum predicted heart rate (HR). An additional group of ten subjects (50-66 years) completed exercise protocols involving bicycle ergometry and stair climbing. Throughout all tests, pacemaker pulse rates and subjects' intrinsic HR were monitored continuously. For the treadmill exercise, the average correlations between the AC and PZ pacemakers' pulse rate and HR for the group as a whole were r = 0.92 and r = 0.82, respectively. Individual subject comparisons were also made between each pacemaker rate and intrinsic HR. The mean difference from intrinsic rate was 11 ppm for the AC pacemaker and 24 ppm for the PZ pacemaker. In addition, the PZ pacemaker's maximal pulse rate was significantly lower (105 +/- 9.6 ppm) than the other two rates (AC 137 +/- 6 ppm; intrinsic HR 129 +/- 2 beats/min). Throughout the bicycle ergometry testing, the intrinsic HR was higher than the AC and PZ pacing rates. However, the AC's rate was significantly higher than the PZ's rate. When subjects ascended stairs, the intrinsic HR and AC rate were closely correlated, but the PZ rate was significantly lower.(ABSTRACT TRUNCATED AT 250 WORDS)

The individual responses were proportional to the physical exertion imposed on the patients. Pacing rates were considered to be appropriate using the chronotropic response zone as a criterion for appropriate rate modulation. A simple walking test utilizing the exercise test facility, results in appropriate optimization of the pulse generator to the individual patient.

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