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South African Medical Journal

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Factors predicting walking intolerance in patients with peripheral arterial disease(PAD) and intermittent claudication

BM Parr, TD Noakes, W Derman

Abstract




Objective. To determine which physiological variables conduce to walking intolerance in patients with peripheral arterial disease (PAD).
Design. The physiological response to a graded treadmill exercise test (GTT) in patients with PAD was characterised. Setting. Patients were recruited from the Department of
Vascular Surgery, Groote Schuur Hospital, Cape Town. Subjects. Thirty-one patients diagnosed with PAD were included in the study. Outcome measures. During a GTT, peak oxygen consumption (VO2peak), peak minute ventilation (VEpeak), peak heart rate
and peak venous lactate concentrations were measured and compared with those from a comparison group. Anklebrachial index (ABI) was measured at rest and after exercise.
During the GTT, maximum walking distance (MWD) and pain-free walking distance (PFWD) were measured to determine walking tolerance. Results. Peak venous lactate concentrations did not correlate significantly with either PFWD (r=–0.08; p=0.3) or MWD
(r=–0.03; p=0.4). Resting ABI did not correlate with either MWD (r=0.09; p=0.64) or PFWD (r=–0.19; p=0.29). Subjects terminated exercise at significantly (p<0.05) lower levels of
cardiorespiratory effort and venous lactate concentrations than did a sedentary but otherwise healthy comparison group: peak heart rate 156±11 v. 114±22 beats per minute
(BPM); p=0.001; and peak venous lactate concentration 9.7±2.7 mmol/l v. 3.28±1.39 mmol/l; p=0.001. Conclusion. Perceived discomfort in these patients is not
caused by elevated blood lactate concentrations, a low ABI or limiting cardiorespiratory effort but by other factors not measured in this study.

South African Medical Journal Vol. 98 (12) 2008: pp. 958-962



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