Platelet Aggregability in Patients with a VVI Pacemaker

Several studies have suggested an increased incidence of thromboembolic events in patients with VVI pacemaker (VVI patients); furthermore, other authors have demonstrated that a treatment with anticoagulants or antiplatelet drugs may be effective in reducing thromboembolic events, thus suggesting an increased formation of platelet thrombi in these patients. In this respect, platelet aggregability was investigated in ten VVI patients and ten age– and sex–matched subjects. β–thromboglobulin (β–Tg) and platelet factor 4 (PF4) plasma levels were determined as weJJ as platelet aggregation induced by ADP, collagen, epinephrine, and arachidonic acid. Plasma β–Tg JeveJs were increased in the patient group (86 ± 24 vs 24 ± 13 ng/mL; P < 0.001) in presence of normal PF4 values (14 ± 11 vs 13 ± 6 ng/mL; NS). Aggregation curves showed abnormal values of maximal amplitude, slope, and lag time. In particular, maximal amplitude was significantJy higher in VVI patients as compared with controls (ADP P < 0.01, collagen P < 0.001, adrenaline P < 0.01, arachidonic acid P < 0.05). These findings strongly suggest an increase of platelet activity in VVI patients.     

THE AGE OF MENARCHE IN SYDNEY SCHOOLGIRLS IN 1973 WITH COMMENT ON THE SECULAR TREND

The age of menarche was investigated in a cross-sectional sample of 840 girls aged 9 to 17 years attending state schools in Sydney in 1973. A probit analysis yielded a mean of 13.26 ± 0.069 yr with a standard deviation of 1.10 yr. Norms for onset of menstruation were estimated for girls 9 to 18 years in 6-monthly intervals. The results were in close agreement with Melbourne data from Towns et al. (1966). A retrospective mean was also found (12.76 yr) which did not differ significantly from a recent similar analysis on Sydney schoolgirls by Harper and Collins (1972). A survey of recent overseas studies using probit analyses found a consensus in Western Europe of 13.0 to 13.4 yr although older and younger means are in evidence elsewhere. An examination of the evidence on a secular trend in menarche in Australia suggested the evidence was not sound enough to allow any positive statement.