Implementation of a group enrollment and open gym format was associated with a significant decrease in wait times for first CR sessions. This CR delivery model may be an option for programs seeking to decrease wait times.

The thromboresistance of 13 potentially blood-compatible polymers was assessed in sheep by determining survival of 51Cr-labeled platelets. Polymer tubing (120-150 cm x 2.0-2.3 mm i.d.) coiled around the neck was incorporated into the circulation through silicone rubber connectors as a carotid artery-external jugular vein shunt. The mean platelet half-life in control animals ("shunt control") was 78.2 +/- 2.8 (SEM) hours. Eleven of the 13 polymers tested significantly shortened platelet half-life. Polyvinyl chloride (T1/2 = 45.4 +/- 3.0 hours), polyperfluoro ethylene (T1/2 = 47.0 +/-1.6 hours), and a polymethylacrylate (PMA)/acrilonitrile copolymer (T1/2 = 50.7 +/- 7.0 hours) produced the greatest shortening. Only silica-free polydimethyl siloxane (T1/2 = 74.7 +/- 4.9 hours) and PMA (T1/2 = 81.5 +/- 3.4 hours) were indistinguishable from shunt controls. Pretreatment of PMA tubing with autologous plasma in a paired trial significantly increased platelet half-life (P less than 0.05 vs. untreated PMA). This system offers an economical, reproducible, sensitive, and biologically relevant method for assessment of the reactivity of artificial surfaces with platelets.

There was wide variability in HR acceleration at the onset of exercise in this apparently healthy cohort. A lower increase in HR during the first minute of exercise was associated with a better CVD risk profile, including higher cardiorespiratory fitness, in apparently healthy individuals. These data suggest a greater parasympathetic influence at the onset of exercise may be protective in an asymptomatic population.

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