Search

The Telesat Canada communications satellite system has been in commercial operation since January 1973. Three ANIK A series satellites and one ANIK B satellite have been launched successfully and some 107 earth stations are now in service. Commencing in 1981 a new series of satellites designated ANIK C will be brought into service. This paper will briefly review the considerations which led to these system plans and provide a preliminary overview of the system features and performance objectives of the proposed ANIK C satellite and associated earth stations.

The effects of a 6-week program of vigorous exercise were studied in 14 non-obese females aged 22--26. Preceding and following a regimen consisting of 30--45 min of jogging 5 days per week, treadmill performance, body weight, total plasma cholesterol, and plasma high density lipoprotein (HDL) cholesterol were assessed. Aerobic performance improved markedly after training as demonstrated by a reduced heart rate at each submaximal treadmill workload, and by an increase in maximal attainable workload. In the absence of a significant change in body weight, total cholesterol fell significantly after training (171 +/- 6 vs 161 +/- 5 mg/dl, P less than 0.05) whereas HDL cholesterol was not significantly altered (63 +/- 5 vs 58 +/- 3 mg/dl). The ratio of total cholesterol to HDL cholesterol fell insignificantly (2.92 +/- 0.19 vs 2.86 +/- 0.14). Our findings differ from prior reports of elevations of high density lipoprotein levels following physical conditioning in men. We suggest that hormonal or other factors leading to higher baseline levels of HDL in women counteract the expected alterations in lipoprotein metabolism induced by physical training.

Myocardial infarct extension, defined as reelevation or reappearance of creatine phosphokinase-MB (CK-MB) 48 hours after the onset of symptoms, was evaluated prospectively in 56 consecutive patients with acute myocardial infarction. Myocardial infarct extension occurred in eight patients (14%). The sensitivity, specificity and predictive accuracy in the diagnosis of myocardial infarct extension were 63%, 85% and 42%, respectively, for recurrent chest pain requiring morphine; 50%, 65% and 19% for recurrent ST-segment elevation on routine 12-lead ECGs; and 88%, 63% and 28% for reelevation of total CK. Three of the eight episodes of extension were clinically silent. Four of eight patients (50%) with extension died, compared with one of 46 patients (2%) without extension (p = 0.0009). CK-MB persisted for 72 hours or longer in 16 patients and identified seven of eight patients who subsequently had infarct extension. We conclude that myocardial infarct extension is an infrequent complication of acute myocardial infarction and is associated with a very high mortality rate. Persistence of CK-MB for 72 hours or more identifies a subgroup of patients at high risk for subsequent infarct extension and death.

The specificity of serum CPK-MB for acute myocardial infarction was examined by retrospective analysis of 401 consecutive patients admitted to Coronary Care Unit over a three and one-half year period with suspected infarction in whom the isoenzyme was subsequently detected. Four patients (1 per cent) who died during the hospital admission had no autopsy evidence of acute myocardial infarction. All four had experienced mild iatrogenic cardiac trauma, following which serum CPK-MG persisted for at least 24 hours. In one patient, a permanent pacemaker had been inserted by the transmediastinal approach. Two patients had been subjected to closed chest cardiac massage and intracardiac puncture, and one to external cardiac massage alone. The findings suggest that persistent identification of serum CPK-MB, although specific for myocardial necrosis, cannot be regarded as diagnostic of myocardial infarction. The implications of this are important to treatment of patients after cardiopulmonary resuscitation and operative trauma to the heart.