EurJ VascSurg 4, 603-606(1990)

Assessment of Intermittent Claudication by Quantitation of Exerciseinduced Microalbuminuria N. C. Hickey, C.P. Shearman, P. Gosling 1 and M.H. S i m m s Departments of Surgery and 1Biochemistry, Selly Oak Hospital, Birmingham, U.K. Urinary albumin excretion rates, expressed as albumin-creatinine ratios (ACR, mg/mmol) were measured beforeand after exercise in 23 claudicants and 10 controls. The mean (range) resting ACRs in the claudicants and controls were 4.42 (0.2-34.6) and 0.77 (0.3-2.8) respectively (P < 0.001). ACR increased after exercise by a mean of 153% in claudicants to 9.7 (0.2-48.1; P < 0.001) with no change in controls, 0.79 (0.2-2.1). In patients with claudication there was a positive correlation between ankle pressure recovery time and the relative increase in ACR after exercise (r = 0.64, P < 0.01). The post-exercise increase in ACR was reduced in all nine patients who underwent bypass surgery. Measurement of ACR after exercise appears to be related to severity of muscle ischaemia and may assist in the assessment of pat&nts with intermittent claudication. Key Words: Intermittent claudication; Proteinuria.

Introduction

Patients and Methods

Intermittent claudication is a common manifestation Twenty-three patients (three female; mean age 66.2 of peripheral vascular disease, affecting at least 5% of years, range 49-80) with intermittent claudication males over the age of 50.1 Putative treatments include were studied. Claudication had been previously diagexercise, drugs, transluminal angioplasty and bypass nosed by history, a resting ankle-brachial pressure surgery. It is essential to have a reproducible m et hod index (ABPI) of less than 0.8 and an ankle systolic of assessment that correlates with disease severity so blood pressure fall of greater than 3 0 m m H g after a that the benefits of these suggested therapies can be s t a n d a r d 1 min exercise test. 9 The time taken for the determined objectively. ankle pressure to return to the resting level (pressure Microalbuminuria is the name given to pathologi- recovery time, PRT) was also recorded. Severity of cal levels of urinary albumin, too low to be detected by symptoms varied, walking distances ranging from 25 dip-sticks. Microalbuminuria occurs after burn injury, to 400m. Ten healthy volunteers (one female; mean trauma, pancreatitis and surgical operations, the age 62.1 years, range 51-81), in w h o m claudication degree of which is related to the severity of the insult was excluded by ABPI measurement and exercise testand appears to have prognostic implications. 2-4 It ing, acted as controls. All patients and controls were results from an increase in the glomerular filtration of normotensive (diastolic BP < 90 mmHg), non-diabetic albumin 5 and probably reflects a generalised increase (normal random blood glucose), and had a normal in vascular permeability to macromolecules.6" 7 serum creatinine. Urinary albumin excretion increases after exercise Having emptied their bladders, subjects rested in claudicants. 8 This study was undertaken to deter- for I h then emptied their bladders again, and a midmine wh eth er these exercise-induced changes in stream specimen of urine (MSU) was obtained. Suburinary albumin excretion could be employed as a jects then walked at 3 km/h on a treadmill with a 10° quantitative assessment of intermittent claudication. incline, claudicants until stopped by pain, and controls for 4 min (the mean walking time of the Please address all correspondenceto: N.C. Hickey, Department of claudicant group). After resting for a further 1 h, a Surgery, SellyOak Hospital, BirminghamB296JD, U.K. second MSU was obtained. 0950-821X/90/060603+04$03.00/0© 1990Grune & StrattonLtd

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Nine of the 23 patients underwent bypass surgery (six aorto-bifemoral and three femoro-popliteal grafts). They returned 3 months later and the tests were repeated, the patients walking the same distance as they had preoperatively. Urinary albumin was measured by radioimmunoassay (Diagnostic Products Corporation, Wallingford UK) and expressed as the urinary albumincreatinine ratio (ACR) in mg/mmol to compensate for changes in urinary flow during the investigation (normal upper limit of ACR = 0.95). Mean (range) values were calculated and differences between groups compared using the Wilcoxon signed rank test.

Results

The mean resting ACR was significantly higher in claudicants (mean 4.4, range 0.2-34.6) compared to controls (0.77, 0.3-2.8; P < 0.001). After exercise, ACR increased in claudicants by a mean of 153% (9.7, 0.248.1) but there was no significant change with exercise in the control group (0.79, 0.2-2.1; Fig. 1). ACR values

varied considerably in the claudicants and a logarithmic scale was required to plot all the data on a single graph. The post-exercise increase in ACR was, however, less than 20% in eight of the ten controls and above this figure in 19 of the 23 claudicants. In nine claudicants with bilateral (aorto-iliac) disease, the increase was over 100%. There was a positive correlation between PRT and the percentage change in ACR that occurred after exercise in the 23 claudicants (Fig. 2). ACR was not related to systemic (brachial) blood pressure, which did not alter significantly during the test w h e n compared to controls. In all nine patients who underwent bypass surgery, symptoms improved and the ABPI increased by a mean value of 0.37 (range = 0.29-0.51). Prior to surgery, the ACR in this group had increased from 4.6 (0.2-18.5) to 13.7 (0.24-48.1; P < 0.05) following exercise. The resting ACR following surgery (5.4, 0.5-24.8) was not significantly different from the preoperative value, but the increase with exercise was reduced to 8.43 (0.42-27.2) and this change was no longer significant. The exercise-induced increase in ACR was reduced in all nine patients when compared to the changes seen preoperatively (Fig. 3).

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