The peripheral blood flow in intermittent claudication. IV. The significance of the claudication distance

Skeletal muscle metabolic changes in peripheral arterial disease contribute to exercise intolerance: a point-counterpoint discussion

Patients with claudication have a marked impairment in exercise performance. Several factors contribute to this limitation, including reductions in large vessel blood flow and oxygen delivery as well as metabolic abnormalities in skeletal muscle. The relative contribution of these factors and their role in the pathophysiology of the exercise limitation is discussed using a point-counterpoint approach. Future directions for research conclude the discussion.

The impact of peripheral arterial disease: A proposal for a new classification

Clasically, intermittent claudication, an intermediate stage in peripheral arterial disease, has been considered as a benign condition when considering only the muscular pain on walking. In this paper our aim is to attract attention about the effects linked to ischemic pain and the oxidative injury resulting from episodes of ischemia/reperfusion. Throughout this process alterations in calcium homeostasis as well as uncontrolled generation of reactive oxygen species, in association with the mitochondrial dysfunction and inflammatory phenomena, could lead to accelerate atherosclerosis, with an increased cardiovascular risk stated by means of a reduced ankle-brachial index. Taking this idea into account we propose a possible new classification for the management of the peripheral arterial disease, combining the Fontaine and Rutherford classifications and thinking about the described systemic effects in order to change the traditional management of peripheral arterial disease.

Transcutaneous PO2 response to transient arterial occlusion in peripheral vascular disease detected by heating power oximeter

Transcutaneous PO2 (TcpO2) was measured in 30 patients with peripheral arterial obstructive disease (PAOD) and in 30 age-matched controls in the hand and foot using a heating power electrode oximeter (HP-E). The HP-E was connected with a software modified monitor to simultaneously record changes in arterial stasis in the skin (TcpO2 mm Hg) and in the underlying tissue 3.5 to 4 mm from the HP-E (TcpO2 mW). In the hands of patients with PAOD, the following was found, lower mean values of the rest flow (R-F) and of the recovery area (Rc-Ar); delayed appearance of both a PO2 decrease after the start of stasis (ODT) and the increased value after the cuff deflation (ORT); and little relevance of flow changes in the tissues under the HP-E. In the foot homolateral to the obstructive lesion, the hemodynamic effects of the stasis were not consistently a result of circulatory insufficiency. In light-medium PAOD the correlation was more significant with the walking-free distance (WFD). However in severe PAOD, the perfusion was usually depressed and the variable values tended to flatten. This study confirmed the diagnostic reliability of this test in PAOD patients. Furthermore simultaneous exploration of two microvessel levels increased its diagnostic possibilities.

Correlation of hemodynamic and functional variables with the angiographic extent of peripheral arterial occlusive disease

The aim of the study was to determine whether hemodynamic and functional variables are related to the angiographic extent of lower limb atherosclerosis. In 150 patients with stable intermittent claudication, the Bollinger angiogram score was compared with the resting Doppler pressure values, and the initial claudication distance (ICD) and absolute claudication distance (ACD) with treadmill exercise. The extent of lower limb atherosclerosis correlated significantly with the age of the patients and the duration of the claudication. The angiogram scores of the patients were negatively correlated with the ankle systolic blood pressure (SBP) and the ankle/brachial index (ABI). In a multiple regression analysis, ABI was the most predictive variable for the angiographic severity of disease. ICD, ACD and work on the treadmill failed to correlate with the angiogram summation score. If patients were classified into groups for those with iliac or femoropopliteal disease, a weak correlation between ACD and femoropopliteal angiogram score was found. The comparison between Doppler measurements and treadmill exercise testing showed no significant correlation between SBP/ABI of the more diseased limb and ICD. However, both SBP and ABI did correlate significantly with ACD (r = 0.16, p < 0.05 and r = 0.20, p < 0.01, respectively). In conclusion, SBP and ABI are reliable parameters for indirect assessment of the angiographic extent of lower limb atherosclerosis. In contrast, the walking capacity of claudicant patients is independent of the angiographic severity of the disease.

Poor reproducibility of exercise test in assessment of claudication

To assess reproducibility of the exercise test in intermittent claudication, a prospective, comparative, randomized study was undertaken. Ten patients with stable intermittent claudication of ischaemic origin were exercised on a flat surface (0-Ex), with 12% steady inclination (12-Ex) and with progressively increasing inclination (p-Ex) in a random order during three different sessions. The ankle-brachial index (ABI) at rest and after exercise (rABI, exABI), initial and maximum walking distance (IWD, MWD) and metabolic equivalent (MET) were obtained as the main outcome measures. The results were analysed using intraindividual coefficients of variation (CVs) and standard deviations (SDs). The ABI values of the worst extremity were used in evaluation of results. Reproducibility of the exercise ABI appeared to be good, especially during progressively increasing exercise, the mean CV being 9 +/- 5%. The best mean CV was observed during p-Ex (16% +/- 14%) for maximum walking distance. The mean CV for initial walking distances ranged from 30% to 54%. Treadmill exercise testing to measure walking distances is highly inaccurate and the value of exercise on the flat treadmill should be questioned. Graded exercise appeared to be the most reproducible in this respect. The ABI after exercise, however, was a reliable single parameter when assessing arterial insufficiency causing decreased walking capacity.

Practical equations to predict claudication pain distances from a graded treadmill test

Treadmill testing is used to estimate the severity of claudication, but routine use is not practical or cost-effective in all settings. Thus, the purposes of this study were: (1) to develop and cross-validate prediction equations for treadmill claudication pain distances in a heterogeneous cohort of peripheral arterial occlusive disease patients, and (2) to determine if the regression equations were more accurate in assessing claudication distances than self-reported distances of patients. Medical history, vital signs, resting ankle/brachial systolic pressure index (ABI), and claudication distances during a graded treadmill test were obtained on a validation group of 178 claudicants and on a cross-validation group of 94 claudicants. The independent predictors of claudication pain distances of the validation group were ABI, body mass index, gender, and current smoking status, with multiple correlation coefficients of R = 0.73 and R = 0.82 for the distances to onset and to maximal pain, respectively. These equations were successfully cross-validated on an independent group of claudicants, as the predicted distances to onset of claudication pain (167.2 +/- 102.6 m) and to maximal pain (354.6 +/- 154.3 m) were similar (p = 0.99) to measured distances (169.1 +/- 127.8 m and 356.6 +/- 181.0 m, respectively). However, the self-reported distances to onset (89.5 +/- 126.3) and to maximal claudication pain (189.2 +/- 284.3) were 1-2 blocks less than either the measured or predicted distances (p < 0.01). It is concluded that claudication pain distances during an incremental treadmill test can be more accurately estimated from a composite of variables obtained during medical screening than by relying on the self-report of patients. Consequently, in clinical settings where treadmill testing is impractical, the functional severity of claudication can be assessed without exercise testing.

Comparison of graded versus constant treadmill test protocols for quantifying intermittent claudication

The standard method for quantifying the symptoms of intermittent claudication is by using treadmill walking distance. It has recently been suggested that a graded exercise test is much more reproducible than a constant load exercise test. Graded protocols have also been claimed to abolish the placebo effect that has been reported with the constant load test. The reproducibility of absolute claudication distance (ACD) and initial claudication distance (ICD) using a constant load was compared to the graded load treadmill protocol. Fourteen patients (mean age 66 years) with varying severity of stable intermittent claudication were tested using a constant load (3.2 km/h, 10% gradient) and a graded load (3.2 km/h, 0% gradient increasing by 3.5% every 3 min). Patients were tested twice using each protocol in a random sequence, with a minimum 2 day interval between visits. Intra-class correlation coefficient (R) with a constant load protocol for ICD and ACD was R = 0.68, R = 0.93, respectively. With a graded protocol R = 0.84 for ICD and R = 0.98 for ACD. Relative coefficient of repeatability for ICD and ACD during constant load tests were 1.47 and 1.90 respectively and with a graded load test were 1.69 and 1.52 respectively. It was concluded that the graded load test was more reproducible than the constant load test but only by a small margin, whilst ACD was much more reproducible than ICD using either protocol.

Effect of felodipine on regional blood supply and collateral vascular resistance in patients with peripheral arterial occlusive disease

This double-blinded, randomized, placebo-controlled study was designed to investigate the acute effect of felodipine on regional blood supply and collateral vascular resistance in patients with peripheral arterial occlusive disease (PAOD). Thirty men with PAOD were treated with a single dose of 5 mg felodipine or placebo. Systolic blood pressure (SBP), Doppler ankle pressure (DAP), calf blood flow (CBF) by venous occlusion plethysmography and calf transcutaneous oxygen tension (tcpO2) were measured during a cycle ergometry. Felodipine reduced SBP significantly (from 149 to 136 mmHg, p < 0.05), while placebo did not. DAP increased slightly but not significantly in both groups. The pressure gradient between SBP and DAP fell significantly in the felodipine group (60 vs 39 mmHg, p < 0.01) but not in the placebo group (59 vs 56 mmHg). There was a trend for lower velocity in tcpO2 decrease during the stress test and higher velocity of tcpO2 increase during recovery from exercise in the felodipine group although the differences between both groups were not significant. In the felodipine group, CBF increased by 35.6% (p < 0.05) whereas it did not change in the placebo group. In conclusion, while lowering SBP, felodipine increased slightly, or at least maintained, the blood supply to the calves in PAOD patients, which probably results from reducing collateral vascular resistance.

A meta-analysis of randomized, double-blind, placebo-controlled studies of the effect of buflomedil on intermittent claudication

A meta-analysis was performed on the results of clinical trials of buflomedil in intermittent claudication. The analysis used results from 744 patients enrolled in ten studies, conducted at 42 centers in seven countries. All studies were randomized, double-blind, placebo-controlled trials which measured improvement in "pain-free" walking distance by treadmill ergometry as the primary measure of efficacy. The meta-analysis results were based on "effect size", a standardized difference in mean response between buflomedil and placebo. Results demonstrated a statistically superior response to buflomedil compared with placebo, indicating that the average buflomedil treated patient was likely to have a greater improvement in walking distance than at least 60% of the placebo treated patients. Results were corroborated using various weighting schemes proportional to study quality ratings and sample sizes.

Co-variation between walking ability and circulatory alterations in patients with intermittent claudication

Unselected patients (n = 183) with subjective symptoms of intermittent claudication were examined clinically and by various circulatory tests (calf blood-flow, ankle, toe pressures). The aims of the present study were to evaluate to what extent the central or peripheral circulation is limiting in unselected patients with subjective symptoms of intermittent claudication, to determine the co-variation between the maximum walking capacity and traditional haemodynamical measures mentioned above and to evaluate to what extent a traditional bicycle ergometer exercise test and treadmill walking test give similar information regarding maximum performance. Eighty-five per cent of all patients were or had been smokers and 16% were diabetics. The mean ankle/brachial blood pressure index was 0.58 +/- 0.02 and the average post-ischemic maximum calf bloodflow was 13.3 +/- 0.6 ml/min/100 ml tissue. Leg arterial insufficiency was the limiting factor of walking capacity in 90% of all patients at 87 +/- 2 W corresponding to a walking distance of 282 +/- 13 m, while leg exhaustion was the limiting factor in 80% of the patients during test on the bicycle ergometer at maximum 84 +/- 2W. The mean maximum walking capacity for all patients was 86 +/- 3W and the mean maximum capacity on the bicycle ergometer was 87 +/- 2W. The ankle/brachial index showed only a weak correlation (r = 0.30, p < 0.002) to walking capacity. Our results demonstrate that the maximum walking capacity on a treadmill agrees with mean values of maximum exercise capacity on a bicycle ergometer.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-blind comparison of captopril with nifedipine in hypertension complicated by intermittent claudication

In a double-blind, crossover trial 12 patients with hypertension and peripheral arterial disease were randomized to three months' treatment with captopril 25-50 mg twice daily or nifedipine SR 20-40 mg twice daily. While both treatments were equally effective at lowering blood pressure, postexercise calf blood flow availability was greater during treatment with captopril (P less than 0.04). This was not reflected in walking capacity assessed by treadmill exercise. The results suggest that both captopril and nifedipine are appropriate antihypertensive agents in patients with peripheral arterial disease.

Comparison of three progressive exercise protocols in peripheral vascular occlusive disease

Although claudication pain and hemodynamic responses to exercise are usually clinically assessed via graded treadmill walking, measuring these responses to other commonly performed tasks may yield a more nearly complete evaluation of peripheral vascular occlusive disease. Thus, the purpose of this study was twofold: (1) to determine the reliability of claudication and hemodynamic responses to level walking and stairclimbing and (2) to compare these responses with those obtained with graded walking at similar oxygen consumption. Ten patients with stable claudication symptoms performed graded walking, level walking, and stairclimbing progressive protocols with respective increases in grade, walking speed, and stepping rate on a modified stairclimbing device every two minutes. Similar peak oxygen consumption (13.60 to 14.18 mL/kg/min) was attained with the three protocols (P = NS). Reliability coefficients for the times to onset and to maximal claudication pain during level walking (R = 0.95 and 0.95, respectively) and during stairclimbing (R = 0.92 and 0.82, respectively) were similar to those previously obtained during graded walking. Reliability coefficients for foot transcutaneous oxygen tension during and following level walking (R = 0.78 to 0.96) and stairclimbing (R = 0.65 to 0.98) and for ankle systolic blood pressure following level walking (R = 0.95 to 0.97) and stairclimbing (R = 0.90 to 0.98) were also similar to those previously found with graded walking. Additionally, claudication and hemodynamic measurements were similar among the three exercise protocols. Thus, because graded walking, level walking, and stairclimbing progressive exercise protocols yield reliable and similar information about the hemodynamic severity of peripheral vascular occlusive disease, only one is needed for evaluation.

Effects of handrail support on claudication and hemodynamic responses to single-stage and progressive treadmill protocols in peripheral vascular occlusive disease

Because handrail support reduces the energy cost of treadmill walking, claudication and hemodynamic responses of patients with peripheral vascular occlusive disease should also be affected. Furthermore, the reliability of the test results may be reduced unless the same pressure is applied to the handrails over repeated tests. The effect of handrail support on claudication and hemodynamic responses, and on their reliability, were examined during single-stage (2 mph, 12% grade) and progressive (2 mph, 0% grade with 2% increase every 2 minutes) treadmill protocols. Ten patients with stable disease performed both protocols 3 times, separated by 1 week, with and without handrail support. Claudication pain distance and maximal walking distance were greater (p less than 0.05) when handrail support was permitted, and they increased (p less than 0.05) over repeated tests of each protocol. No increase was noted over the tests without support. The responses and reliability of foot transcutaneous oxygen tension, ankle systolic pressure and ankle/brachial systolic pressure index after exercise to maximal tolerable pain were not affected by handrail support. Because claudication distances were altered, it is concluded that handrail support should not be allowed when assessing claudicants, unless balance cannot otherwise be maintained.

Conservative drug treatment in patients with moderately severe chronic occlusive peripheral arterial disease. Scandinavian Study Group

A double-blind, parallel group, multicenter clinical trial of pentoxifylline compared with placebo enrolled 150 patients with moderately severe chronic occlusive arterial disease (COAD) at three centers in Scandinavia. The study consisted of a 4-6 week single-blind, placebo-controlled run-in phase, during which the stabilization of the initial claudication distance of all patients was assessed before randomization to a 6-month double-blind observation period. The diagnosis of COAD was established by clinical findings, conventional angiography, and noninvasive peripheral Doppler pressure assessment at rest and after exercise. The results of the overall intention-to-treat analysis of the study population show statistically significant superiority of pentoxifylline over placebo for all absolute claudication distance summary and end point measures. By using two clinically relevant parameters, which are a resting ankle/arm pressure ratio 0.8 or less and a duration of COAD for greater than 1 year, a target population could be defined in whom trial results became highly significant. For nontarget patients with mild COAD, we conclude that basic therapeutic measures should include the treatment of risk factors and the initiation of physical training. For target patients, however, a multifactorial therapeutic approach, including the use of pentoxifylline, is justified.

Drug treatment of intermittent claudication: a critical analysis of the methods and findings of published clinical trials, 1965-1985

1. All trials of drug therapy for intermittent claudication published in English during the period 1965-1985 were reviewed. A total of 75 trials had studied 33 different pharmacological agents. Treadmill exercise, the most reproducible method of evaluating symptoms in this condition, was used in 49% of trials. 2. Oxpentifylline was the drug that had been most frequently studied. In seven placebo-controlled trials the average response to oxpentifylline, compared with placebo and weighted for sample-size, was 65% improvement in claudication distance. There was, however, a significant negative relation between sample-size and response (rs = -0.79, P less than 0.05), suggesting that this estimate was likely to have been biased by non-publication of negative results. 3. One third of all trials were uncontrolled; 84% of these reported benefit from drug treatment, compared with 32% of placebo-controlled trials (P less than 0.001). Sample-sizes varied from seven to 227 patients; 31% of trials reported data from less than 20 patients and these were likely to have had insufficient statistical power. 4. Overall, 57 of the 75 trials (76%) had at least one of the following deficiencies: an uncontrolled design; not double-blind; failure to use treadmill exercise; less than 20 patients included in the analysis. Thus, a priori three-quarters of all trials were unlikely to have made a satisfactory assessment of drug efficacy. 5. The information available does not establish convincingly that any drug consistently improves exercise performance in intermittent claudication. In view of the deficiencies in previous trials, we propose guidelines for future studies with regard to trial design, sample-size and methods of exercise testing.

Placebo-controlled comparison of captopril, atenolol, labetalol, and pindolol in hypertension complicated by intermittent claudication

In a six month placebo-controlled cross-over trial twenty patients with hypertension and peripheral arterial disease were randomised to captopril 25 mg twice daily, atenolol 100 mg once daily, labetalol 200 mg twice daily, or pindolol 10 mg twice daily for one month. Although all treatments were equally effective at lowering blood pressure, pain-free and maximum walking distances on a treadmill were decreased by atenolol, labetalol, and pindolol, but not by captopril. Post-exercise calf blood flow availability was impaired by atenolol, labetalol, and pindolol, but not by captopril. Despite ancillary characteristics of cardioselectivity, intrinsic sympathomimetic activity, or combination with alpha-blockade, beta-blockers seem to impair the lower limb circulation in such patients, whereas captopril seems to preserve it, possibly by maintaining the collateral blood supply.

The effect of beta-blockade on leg blood flow in hypertensive patients with intermittent claudication

The present study was designed to assess the short-term effects of beta-blocking antihypertensive treatment on leg blood flow in patients with peripheral artery disease. Seven patients with intermittent claudication were randomly allocated to treatment with atenolol 100 mg or pindolol 10 mg. Patients switched therapy after one month of treatment. Venous occlusion plethysmography on the calves was used to assess the effects on leg blood flow after one and two months of treatment. The average 10% reduction of the systolic and diastolic blood pressures was not associated with any reduction of blood flow at rest. There was on average 3.4 ml reduction of peak flow which had no influence on the painfree or total walking distance.

The effect of withdrawal of beta-adrenergic blockade on intermittent claudication

Twenty-eight patients with intermittent claudication were studied before and one month after withdrawal of treatment with beta-adrenergic blocking drugs for hypertension, coronary heart disease or both. Heart rate, blood pressure, ankle/arm systolic blood pressure ratio and ankle pulse volume recording (PVR) at rest and after treadmill exercise were recorded, as well as walking distance, time of recovery from subjective symptoms, restitution time of pressure ratio and PVR. A control group of 14 patients, whose beta-adrenergic blocking drugs were not withdrawn, was also included. The result can be summarized as showing that withdrawal of beta-blockade was not demonstrably advantageous in patients with intermittent claudication. Significant improvement was observed only during the first month of the trial, a change which was independent of withdrawal of beta-blockade. The relief of subjective symptoms after exercise occurred significantly faster after withdrawal of nonselective beta-blockade. Otherwise, there was no difference between nonselective and cardioselective beta-adrenergic blocking drugs.

The monark bicycle ergometer in screening arterial patients

In patients with peripheral arterial disease, maximum walking distance on a treadmill is commonly used for studying the effect of exercise on ankle systolic pressure. Exercise on the Monark bicycle ergometer for 1 min at a workload of 1 kp and cycling at 20 kph has been compared with treadmill walking in 30 patients presenting with calf pain on exercise at the vascular clinic and in 6 normal volunteers. The bicycle test produced a significant fall in ankle systolic pressure in all patients with advanced arterial disease. There was no statistical difference in the results obtained on the bicycle compared with the treadmill. There was better patient compliance with the bicycle test. The Monark bicycle ergometer, a simple inexpensive instrument, is a viable alternative to the treadmill for exercising arterial patients.

Standard exercise test to assess peripheral arterial disease

The fall in ankle systolic pressure after exercise serves as an objective indicator of the severity of haemodynamically important peripheral arterial disease. Twenty-six patients were studied to establish the effects of different work loads on the pressure response and to develop a test to standardise these effects. The patients walked for one or two minutes at 4 km/h and one or two minutes at 6 km/h, and the fall in pressure was the same when measured immediately after exercise. The time taken for the pressure to return to the pre-exercise value varied. As the fall in pressure occurs after only one minute of exercise at 4 km/h on a 10% slope, this might be adopted as a standard test. It is acceptable to the patient, since claudication, angina, and shortness of breath rarely occur. It is sensitive enough to detect mild or asymptomatic disease and is useful in following up patients.

A gravimetric plethysmograph and its evaluation in clinical use

A gravimetric plethysmograph, the technique of its use and its evaluation in vascular surgical practice are described. The instrument measures flow by the increase in leg weight (rather than volume) produced by an increase in blood content resulting from venous occlusion. The instrument was found to be convenient to use and satisfactory records were obtained in 88% of patients. Values for flow at rest and during reactive hyperaemia were clearly related to the presence of indications for surgical treatment and were similar to those reported by other workers. It is suggested that a peak hyperaemic flow of greater than 15 g 100 ml-1 min-1 may indicate that there are no indications for surgical treatment. The changes in hyperaemic flow values after treatment were clearly related to the symptomatic improvement resulting from it. It is concluded that the gravimetric plethysmograph is suitable for use in the assessment of patients with obliterative arterial disease of the legs.

The clinical use and value of non-invasive diagnostic techniques in peripheral arterial occlusive disease

The clinician confronted with the need for the objective evaluation of peripheral vascular problem has a variety of simple noninvasive techniques available which can prove highly useful in the early detection of occlusive disease, its functional assessment and in the selection of those problems which requires further definitive evaluation by angiographic methods. The non-invasive techniques offer the additional advantage of applicability to the serial evaluation of patients before and after surgical or medical therapy.

Muscle blood flow during exercise in intermittent claudication. Validation of the 133-xenon clearance technique: clinical use by comparison to plethysmography and walking distance

Pathophysiological considerations predict that exercise blood flows at comparable work loads must always be reduced in claudicants in comparison to normal subjects. The present study verified that the exercise blood flow determined by 133 xenon clearance measurements in the gastrocnemius muscle in claudicants and in a control group differed widely.

As expected, a statistically significant correlation was found between the first flow by plethysmography and the maximal exercise blood flow determined by the 133 xenon clearance technique in the patients and for the whole material (but not for the control group alone). The exercise blood flow determined by 133 xenon clearance in the claudicants was statistically significantly correlated to the walking distance, measured on a treadmill, while the postexercise blood flow as measured by plethysmography was not. This finding establishes the concept, that the 133 xenon clearance technique can be applied in quantitating the degree of arterial insufficiency.

Muscular angiographic patterns in lower extremities before and after exercise: technic for study of blood flow and diagnostic applications

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