There is an increased rate of rise in VO2 relative to work rate during exercise in patients with McArdle's disease. There is also a greater rise in catecholamines, which may be the result of a physiological response to substrate starvation, and is likely to contribute to the increase in VO2.

During constant work-rate exercise above the lactic acidosis threshold, oxygen consumption fails to plateau by 3 minutes, but continues to rise slowly. This slow component correlates closely with the rise in lactate in normal subjects. We investigated if oxygen consumption during constant work-rate exercise could rise after 3 minutes in the absence of a rise in lactate. We studied five patients with McArdle's disease, one patient with phosphofructokinase deficiency and six normal subjects. Subjects performed two 6-minute duration constant work-rate exercise tests at 40 and 70% of peak oxygen consumption. During low-intensity exercise, oxygen consumption reached steady state by 3 minutes in both groups. Lactate rose slightly in control subjects but not in patients. During high-intensity exercise, oxygen consumption rose from the third to the sixth minute by 144 (21-607) ml/minute (median and range) in control subjects and by 142 (73-306) ml/minute in patients (p = not significant, Mann-Whitney U test). Over the same period, lactate (geometric mean and range) rose from 2.68 (1.10-5.00) to 5.39 (2.70-10.00) mmol/L in control subjects, but did not rise in patients (1.20 [0.64-1.60] to 0.70 [0.57-1.20] mmol/L). We conclude that the slow component of oxygen consumption during heavy exercise is not dependent on lactic acidosis.

We investigated venous thromboembolism (VTE) in women on third generation combined oral contraceptives (COCs). A detailed history of risk factors was taken and a thrombophilia screen performed in 163 women (mean age 25.5, range 16-49) suffering VTE on COCs.VTE occurred a median of 12.3 (range 1 -60) months after commencing COC; 59 with DVT, 52 pulmonary embolism (PE) and 44 had both all confirmed by imaging. There were four sagittal sinus, six axillary and one mesenteric vein thromboses. Paradoxical embolism caused myocardial infarction in one and stroke in another. 20% of the women suffered immobilisation by illness or travel before their episode of VTE. The underlying risk factors were history of VTE (1 7%) and thrombophilia (10%) in first degree relatives, obesity (29%) and previous DVT (1.2%).Percentage 95% CI Expected??)

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