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

Abstract

Objective: It is not clear which physiological variables determine 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 characterized.
Setting: Patients were recruited from the Department of Vascular Surgery at Groote Schuur Hospital, Cape Town, South Africa.
Subjects: 31 patients diagnosed with PVD 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. These variables were compared to those measured in a comparison group previously studied in this laboratory. Ankle brachial index 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=008; P=0.3) or PFWD (r=-0.15; P=0.15). 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 vs 114 ±22 bpm p=); and peak venous lactate concentration (9.7 ±2.7 mmol.l-1 vs 3.28 ±1.39 mmol.l-1 ).
Conclusion: Perceived discomfort in these patients is not caused by elevated blood lactate concentrations, a low ABI or by limiting cardiorespiratory effort but must be due to other factors not measured in the present study.