to the life and limb of patients with such low pressures.8However, others found a better prognosis.9 Also, manypatients with toe pressure of 30 mm Hg or less do nothave clinical manifestations of critical ischemia and have abetter prognosis than those with rest pain or skin lesions,9suggesting that some patients have a better tissue perfu-sion. Impaired perfusion and the resulting changes in themicrocirculation play an important role in bringing aboutcritical ischemia and its complications.6,7,10,11 Suchchanges are associated with effects in remote vascular bedsand may be related to the excessively high rates of cardio-vascular events and mortality in patients with peripheralarterial disease.12-14

Abnormalities of various parameters related to micro-circulation have been demonstrated in limbs with arterialdisease. However, no one method has been accepted as aroutine laboratory procedure to evaluate distal perfusion.This is because measurements of microcirculatory parame-ters are more difficult to standardize than pressure mea-surements and are often time-consuming. Pulse waves canbe recorded from the toes quickly and easily with photo-plethysmography.15 Their amplitude is related to bloodflow,16 and therefore, it can be considered to be a crudeindex of distal perfusion. Indeed, pulse wave or pulse vol-ume recordings have been recommended for the assess-ment of circulation in diabetic patients7 and of limbs forsevere ischemia.17,18 We reported that after controlling for toe pressure and ankle/brachial index (ABI), the odds

It is firmly established that patients with peripheralarterial disease have a high incidence of cardiovascularevents and death in addition to a risk of major amputation.The rates of cardiovascular events and mortality aregreater than can be accounted for by the presence of con-ventional risk factors and increase with the severity of theobstruction as assessed with distal pressure measure-ments.1-5 In patients who also have skin ulcers, gangrene,or rest pain, the risks were reported to be extremely high,and their fate was considered to be comparable to that ofpatients with a virulent malignancy.6

The Second European Consensus Document pro-posed ankle systolic pressure of 50 mm Hg or less or toesystolic pressure of 30 mm Hg or less as hemodynamic evi-dence of critical ischemia.7 These criteria were challengedbecause of the finding of a worse than expected prognosis

708

From the Departments of Medicine, Physiology,a and Community HealthSciences,b University of Manitoba, and Vascular Laboratory, St BonifaceGeneral Hospital.a

Competition of interest: nil.Supported in part by a grant from the St Boniface General Hospital

Research Foundation.Reprint requests: Stefan A. Carter, MD, Vascular Laboratory, St Boniface

General Hospital, 409 Tache Avenue, Winnipeg, Manitoba, Canada,R2H 2A6 (e-mail: sacarte@cc.umanitoba.ca).

Copyright © 2001 by The Society for Vascular Surgery and The AmericanAssociation for Vascular Surgery.

0741-5214/2001/$35.00 + 0 24/1/112329doi:10.1067/mva.2001.112329

The value of toe pulse waves in determination of risks for limb amputation and death in patients with peripheral arterial disease and skinulcers or gangreneStefan A. Carter, MD,a and Robert B. Tate, PhD,b Winnipeg, Manitoba

Objectives: The purpose of this study was to determine whether the presence of low amplitude of pulse waves recordedfrom the toes is related to the risk of subsequent amputation and death in patients with skin ulcers or gangrene andperipheral arterial disease, and how the risk of low wave amplitude relates to the risk associated with low peripheralpressures.Methods: A total of 309 patients with 346 limbs with skin lesions and arterial disease referred to the vascular labora-tory were followed up for an average of 5 years (range, 1-8 years). Measurements were carried out to obtain ankle andtoe pressures, pressure indices, and toe pulse wave amplitude. These variables were related to the risks of major ampu-tation and total and cardiovascular death by means of the Cox proportional hazards model.Results: Low toe pulse wave amplitude (≤ 4 mm) was associated with increased risk of amputation (relative risks 4.20in all limbs and 2.63 in those with toe pressure ≤ 30 mm Hg; P < .01). Wave amplitude remained significantly associ-ated with increased risk of amputation after controlling for each pressure variable (P < .01). Low pulse wave amplitudeand toe/brachial index were associated with increased risks of both total and cardiovascular death in all patients (rel-ative risks ranged from 1.43-1.73; P < .05) and in those with toe pressure of 30 mm Hg or less (relative risks 1.56-1.90; P < .05).Conclusions: Low toe pulse wave amplitude is related significantly to increased risks of amputation and death in patientswith skin lesions and arterial disease. The presence of low wave amplitude provides significant information in additionto peripheral pressures with respect to the risk of amputation. (J Vasc Surg 2001;33:708-14.)

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for the presence of rest pain or skin lesions were aboutfour times higher in the presence of pulse waves with lowamplitude compared with patients with high amplitude.15

The primary aim of this study was to assess whether thepresence of a pulse wave of low amplitude in the toes ofpatients with arterial obstruction and skin lesions isrelated to the subsequent limb amputation and death. Wealso wanted to determine whether combination of mea-surements of pressure and of pulse wave amplitude pre-dicts prognosis better than pressure measurements alone.

PATIENTS AND METHODS

Patients studied. The study was approved by TheCommittee on the Use of Human Subjects in Research ofthe University of Manitoba. A total of 333 patients (378extremities) with skin ulcers or gangrene were referred tothe vascular laboratory at St Boniface General Hospitalover a period of 41⁄2 years. In 32 limbs of 24 patients, theABI and toe/brachial index (TBI) were greater than 0.90and 0.50, respectively, indicating either the absence ofovert arterial disease or the presence of mild obstruc-tion.19,20 These patients were excluded from further study.The remaining 346 limbs of 309 patients were consideredto have significant arterial disease. Severe obstruction wasdefined by the presence of toe pressure 30 mm Hg or less.This subgroup consisted of 234 limbs of 217 patients.

Measurements. Pressure and pulse wave measure-ments were carried out after each patient rested for at least20 minutes with the body and extremities covered with aheating blanket to buffer the measurements from thepotential effects of cool outdoor temperatures.15,21 Theroom temperature was approximately 23ºC.

Ankle, toe, and brachial systolic pressures were mea-sured with the use of the previously reported meth-ods.15,19,20 The ABI and TBI were calculated as the ratiosof the ankle and toe pressure to the brachial systolic pres-sure, respectively. In 60 limbs (17%) of 52 patients, eitherankle pressures could not be measured because the flowcontinued despite the inflation of the blood pressure cuffsto 300 mm Hg or the measurements were clearly unreli-able because of “partial arterial wall incompressibility”when normal or near normal ankle pressures were associ-ated with grossly abnormal monophasic arterial flowsounds over the ankle arteries. Ankle pressures in theselimbs were considered as missing values. Toe pressureswere measured routinely in the hallux. In 21 limbs, pres-sure was measured in the second toe because of previousamputation or lesions of the hallux.20 In 16 limbs (4.6%),lesions or amputations precluded measurement of pressurein any digit.

Pulse waves were recorded from the plantar aspect ofthe toes with photocell plethysmography, and their ampli-tude was measured in millimeters of deflection asdescribed previously.15 The mean of measurements of atleast three pulse waves in the toe with the wave with thelargest amplitude was used. In 16 limbs (4.6%), wavescould not be recorded because of extensive skin lesions oramputation of all digits.

Follow-up and statistical analysis. The patients inthis prospective cohort study were followed up with tele-phone interviews and the review of charts and healthrecords. The therapy of the patients including decisionsconcerning arterial reconstruction, amputation, and treat-ment of those who did not undergo revascularization wasmanaged by the patients’ attending physicians. Informa-tion was sought about the occurrence and cause of death,major amputation, and reconstructive vascular surgery or angioplasty. A total of 213 patients (69%) died duringfollow-up. Those who did not die were followed up for anaverage of 5 years (range, 1-8 years). The follow-up was99% complete to 3 years and 95% to 4 years.

Data of continuous variables are reported as mean ±SEM unless otherwise indicated. Pearson correlationcoefficients were calculated for the relationships of thecontinuous variables. The significance of the differencesbetween pairs of means was tested with the two-sampleStudent t test.

The Cox proportional hazards model22 was used toassess the relative risks of major amputation and total andcardiovascular death associated with demographic and clin-ical characteristics, with categoric variables of pressure cut-off values, and with the pulse wave amplitude 4 mm or less.The categoric variable, a pulse wave amplitude of 4 mm orless, was previously demonstrated to be associated withincreased odds ratios for the occurrence of rest pain, skinlesions, or both.15 The reproducibility of this discriminantvalue of amplitude was assessed previously.15 It was foundthat in 96% of the limbs the amplitude remained below orabove 4 mm when tested on separate days. Interactionbetween the pressure variables and wave amplitude wastested for in the Cox models. The relative risks and 95%CIs were determined in the whole group with arterial dis-ease and in the subgroup with severe disease (toe pressure≤ 30 mm Hg). Kaplan-Meier curves23 were constructed toillustrate the relationship of cutoff values of pressures andof pulse wave amplitude to the outcomes.

In patients who had both legs with skin lesions in thestudy, the data from the limb with more severe diseasewere used in the assessment of the risks for death. Thelevel of significance was set at 0.05 for all analyses.

RESULTS

The objective of this study was to assess the relation-ship of pulse wave amplitude, alone and with pressure val-ues, with the outcomes. Therefore, the results given beloware based on 266 limbs (238 patients) in which there werevalid measurements of ankle and toe pressures and of toepulse waves. Implications of excluding the patients inwhom one or more of the three measurements wereunavailable is discussed.

General characteristics of the patientsThere were 139 men and 99 women with the mean

age of 72 years ± SD 10 years and 74 years ± SD 9 years,respectively. Thirty percent were current smokers, 45%were previous smokers, and 25% had never smoked. The

presence of comorbidities was assessed on the basis of theentries in the hospital charts and the physicians’ records.Ischemic heart disease was present in 45% of the patients,cerebrovascular disease in 24%, hypertension and diabeteseach in 56%, and renal failure in 11%.

Hemodynamic characteristicsTable I shows the mean values of pressures and of

pulse wave amplitude and percentages of the limbs belowvarious cutoff values. Although 17% of the limbs in thewhole group had ankle pressure of 50 mm Hg or less,larger proportions had low toe pressure, ABI, TBI, andwave amplitude. In the group with severe disease, propor-tions of limbs below the cutoff values were all larger.

As expected, there were highly significant correlationsamong toe pressures, ankle pressures, and pulse waveamplitude with P equal to .001 or less in all cases. The cor-relation coefficients were 0.69 between ankle and toepressure and 0.66 between ABI and TBI. The correlationcoefficients of ankle pressure and ABI with pulse waveamplitude were 0.37 and 0.39, and of toe pressure andTBI with wave amplitude, 0.50 and 0.53, respectively.Although significant, these values of the coefficients sug-gest that ankle pressures, toe pressures, and wave ampli-tude each provide different information.

OutcomesMajor amputation was carried out during follow-up in

73 limbs (27%). It was primary in 58 extremities and sec-ondary in 15. Arterial reconstructive surgery was done in69 extremities (26%) and transcutaneous angioplasty inthree (1%). The total mortality rate during follow-up was66%. Cardiovascular death accounted for 80% of thedeaths.

The relationship of the demographic characteristics tothe outcomes

The presence of diabetes was associated with the rela-tive risk of 1.8 (95% CI, 1.1-3.0) for major amputation (P < .05), but there was no significant effect of diabetes onthe total or cardiovascular mortality rate. Larger skinlesions (area > 2 cm2) were associated with the relative riskof 3.7 (95% CI, 2.3-5.9) for amputation (P < .001), but

were not associated with significantly increased risk ofdeath. Renal failure was associated with increased risk oftotal and cardiovascular death (relative risks of 4.2 [95%CI, 2.7-6.4] and 5.3 [95% CI, 3.3-8.3], respectively; P <.01). Older patients had a higher total and cardiovascularmortality rate with an increase in risk of about 30% for a10-year increase in age (P < .01). The presence of renalfailure or an increase in age was not associated with signif-icantly higher risks of amputation. Ischemic heart disease,cerebrovascular disease, hypertension, and smoking statuswere not significantly associated with increased risks ofamputation or death.

Toe pressure and wave amplitude were significantlylower in the limbs with larger skin lesions, and ankle pres-sure was higher in the diabetic patients. An increase in agewas associated with a significant decrease in pressures andpulse wave amplitude. There were no significant differ-ences in the pressures or wave amplitude between patientswith and without renal failure. Therefore, the effects ofhemodynamic variables on limb amputations were ad-justed for the presence of diabetes and the size of thelesions. The effects on death were adjusted for the age ofthe patients.

The relationship of the hemodynamic parameters tothe outcomes

The effects on amputation. Table II shows the rela-tive risks of a major amputation associated with the cutoffvalues of the pressures and of the wave amplitude in all266 limbs and in the subgroup of 181 limbs with severedisease. All the pressure values below the cutoff points andthe low wave amplitude were associated with a significantincrease in the risk of amputation. The relative risks asso-ciated with the low wave amplitude were as high or higherthan the highest relative risk among the pressure cutoffpoints. Importantly, Table III shows that when waveamplitude was included in models along with each pres-sure variable separately, the relative risk of amputationassociated with low wave amplitude remained considerablyand significantly increased in each case.

Fig 1 shows the Kaplan-Meier curve for limb survivalfor all limbs and the four curves representing the sub-groups above and below the cutoff values of ABI and wave

JOURNAL OF VASCULAR SURGERY710 Carter and Tate April 2001

Table I. Hemodynamic characteristics of limbs with arterial disease

Arterial disease (n = 266) Severe disease (n = 181)*

% Below % Below Variable Cutoff value Mean ± SEM cutoff value Mean ± SEM cutoff value

Ankle pressure 50 mm Hg 82 ± 2 17 68 ± 2 27ABI 0.50 0.56 ± 0.01 46 0.47 ± 0.01 64Toe pressure 30 mm Hg 25 ± 1 68 13 ± 1 100Toe pressure 20 mm Hg — 50 — 73TBI 0.10 0.26 ± 0.01 39 0.09 ± 0.01 53Wave amplitude 4 mm 13 ± 1 41 7 ± 1 58

*Toe pressure ≤ 30 mm Hg.

amplitude (Appendix, online only). The risk of amputa-tion was the greatest in the limbs in which the ABI andpulse wave amplitude were both below the cutoff points.It was the lowest when both variables were above the cut-off points. In the limbs in which only one variable wasbelow the cutoff point, the risk was intermediate. Lowwave amplitude was associated with a higher rate of ampu-tation in limbs with ABI both above and below 0.50.

The effects on mortality. Tables IV and V show therelative risks for total and cardiovascular death, respec-tively, associated with the cutoff values of the pressuresand of the wave amplitude. There was no significant asso-ciation between the ankle pressure, toe pressure, or ABIand increased risks of total death (Table IV). ABI and toepressure 20 mm Hg or less were significantly associatedwith increased risk of cardiovascular death only in thewhole group (Table V). On the other hand, TBI of 0.10or less and pulse wave amplitude of 4 mm or less were each

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significantly associated with increased risk of total and car-diovascular death in the whole group of 238 patients witharterial disease, as well as in the subgroup of 168 patientswith severe disease. When TBI and amplitude wereincluded together in the models, neither remained signifi-cant. Fig 2 illustrates that there was lower survival inpatients with low pulse wave amplitude and that this sur-vival pattern was similar in patients with TBI below orabove 0.10 (Appendix, online only).

One year after the entry into the study, 23% of thepatients were dead, 15% were alive but had a major ampu-tation, and 62% were alive without amputation. Fig 3 illus-

Table II. Relative risks and 95% CIs of major amputa-tion associated with variables of pressure and pulse waveamplitude

Arterial disease Severe disease Variable (73/266)* (64/181)*

Ankle ≤ 50 mm Hg 2.80 (1.67-4.68)† 1.95 (1.15-3.32)‡ABI ≤ 0.50 4.19 (2.51-6.99)† 2.58 (1.45-4.58)§Toe ≤ 30 mm Hg 4.20 (2.09-8.46)† —Toe ≤ 20 mm Hg 3.24 (1.94-5.41)† 1.96 (1.04-3.69)‡TBI ≤ 0.10 2.77 (1.73-4.41)† 1.76 (1.05-2.95)‡Amplitude ≤ 4 mm 4.20 (2.56-6.89)† 2.63 (1.50-4.59)†

After controlling for the presence of diabetes and the size of the lesions.*Number of amputations/number of limbs at risk.†P < .001.‡P < .05.§P < .01.

Table III. Relative risks and 95% CIs of major amputa-tion associated with low pulse wave amplitude (≤ 4 mm)after controlling for binary pressure variables

Adjusted relative risks for low wave amplitude

Pressure variable Arterial Severe controlled for disease disease in the model (73/266)* (64/181)*

Ankle 3.70 (2.17-6.33)† 2.36 (1.32-4.24)‡ABI 2.67 (1.54-4.65)† 2.15 (1.21-3.81)‡Toe (30 mm Hg) §2.97 (1.69-5.23)† —Toe (20 mm Hg) 3.08 (1.70-5.58)† 2.37 (1.32-4.24)†TBI 3.38 (1.94-5.89)† 2.40 (1.35-4.27)‡

After controlling for the presence of diabetes and the size of the lesions.*Number of amputations/number of limbs at risk.†P <.001.‡P <.01.§In all limbs with arterial disease, there was significant interaction betweentoe pressure (30 mm Hg) and pulse wave amplitude. The relative risk ofamputation was 2.61 (95% CI, 1.50 - 4.55; P < .05) in limbs with toe pres-sure ≤ 30 mm Hg. Among the limbs with toe pressure > 30 mm Hg, therewere only three limbs with pulse wave amplitude ≤ 4 mm, and all threewere amputated within 6 months.

Fig 1. Limb survival in whole group and in subgroups according to ABI and pulse wave amplitude. ABI, Ankle/brachial index.

JOURNAL OF VASCULAR SURGERY712 Carter and Tate April 2001

Fig 3. Total mortality and major amputation rates after 1 year of follow-up according to ABI and pulse wave amplitude. ABI, Ankle/brachial index.

Table IV. Relative risks and 95% CIs of all-cause deathassociated with variables of pressure and pulse waveamplitude

Arterial disease Severe disease Variable (158/238)* (113/168)*

Ankle ≤ 50 mm Hg 1.26 (0.86-1.83) 1.24 (0.83-1.85)ABI ≤ 0.50 1.34 (0.98-1.84) 1.35 (0.91-2.02) Toe ≤ 30 mm Hg 1.10 (0.78-1.56) —Toe ≤ 20 mm Hg 1.33 (0.97-1.82) 1.54 (0.97-2.46)TBI ≤ 0.10 1.43 (1.05-1.96)† 1.58 (1.07-2.34)†Amplitude ≤ 4 mm 1.54 (1.12-2.09)‡ 1.59 (1.08-2.35)†

After controlling for the age of the patients.*Number of deaths/number of patients at risk.†P < .05.‡P <.01.

Table V. Relative risks and 95% CIs of cardiovasculardeath associated with variables of pressure and pulsewave amplitude

Arterial disease Severe disease Variable (127/238)* (94/168)*

Ankle ≤ 50 mm Hg 1.38 (0.91-2.08) 1.30 (0.84-2.01)ABI ≤ 0.50 1.50 (1.05-2.13)† 1.38 (0.89-2.14)Toe ≤ 30 mm Hg 1.27 (0.85-1.89) —Toe ≤ 20 mm Hg 1.47 (1.03-2.10)† 1.57 (0.94-2.63)TBI ≤ 0.10 1.73 (1.22-2.46)‡ 1.90 (1.22-2.96)‡Amplitude ≤ 4 mm 1.66 (1.17-2.35)‡ 1.56 (1.02-2.39)†

After controlling for the age of the patients.*Number of cardiovascular deaths/number of patients at risk.†P < .05.‡P < .01.

Fig 2. Patient survival in whole group and in subgroups according to TBI and pulse wave amplitude. TBI, Toe/brachial index.

trates the fate of the subgroups of patients after 1 year offollow-up according to the cutoff values of ABI and ofwave amplitude. When the ABI was 0.50 or less and toewave amplitude was 4 mm or less, the mortality rate wasabout 50% higher, and the proportion of patients alivewith a major amputation was about three times higherthan among patients with an ABI of 0.50 or less buthigher wave amplitude. Those with an ABI of 0.50 or lessand high wave amplitude had a similar 1-year outcome topatients with an ABI of more than 0.50.

Patients with missing measurementsTo compare the effects of pulse wave and pressure

variables alone and in combinations, we based the previousresults on the 238 patients in whose limbs there were validmeasurements of ankle and toe pressures and of toe pulsewave amplitude. Therefore, patients in whom one or moreof these measurements were missing could not beincluded. The subgroup of the 71 patients with at leastone missing measurement had similar percentages ofpatients with ischemic heart disease, cerebrovascular dis-ease, hypertension, and similar smoking status comparedwith the sample without missing values. However, therewas a higher percentage of diabetic patients (78% vs 56%)and more than twice the percentage of patients with renalfailure. As might be expected, patients in whom toe pres-sure or wave recording or both could not be done hadmore extensive lesions and a higher rate of amputation.On the other hand, those in whom the ankle pressuremeasurements were not valid or could not be obtainedbecause of arterial wall calcification had a higher total andcardiovascular mortality rate, but the rate of amputationwas similar to the rate in the group of patients with all themeasurements. However, the inclusion of all patients withthe missing measurements did not change the percentageof those who died during the first year of follow-up. Thepercentage who were alive but had an amputationincreased from 15% to 19%.

DISCUSSION

The results demonstrate that low amplitude of thepulse waves recorded from the toes is associated with anincreased risk of amputation and of total and cardiovascu-lar death in patients with skin lesions and arterial disease.This is the case in the analyses of all our patients and in thesubgroup with more severe disease (toe pressure ≤ 30 mmHg). Low values of all pressure variables are associated sig-nificantly with an increased risk of amputation. On theother hand, a TBI of 0.10 or less is the only pressure vari-able associated significantly with increased total death andhas the strongest association with increased cardiovasculardeath among the pressure variables. Importantly,increased risks associated with a low wave amplitude, withfew exceptions, are as high or higher than the risks associ-ated with low pressure values. The risk of a major ampu-tation associated with the combination of low ankle or toepressure variables with low pulse wave amplitude is greaterthan the risk associated with individual variables. This

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finding is similar to reports that other measures of micro-circulation are useful in the assessment of prognosis inaddition to pressures.24,25

Although the amplitude of the pulse waves recordedwith plethysmography depends on the characteristics ofthe recording system, it is likely that systems other thanours for recording pulse volume or the wave amplitudewith plethysmography would give similar findings.17,26

Although we chose the cutoff value of 4 mm on the basisof our previous experience,15 other cutoff values (eg, 3 or6 mm) gave similar results. This finding also supports thenotion that analyses of wave amplitude recorded withother systems would produce similar results. Because theamplitude of the waves and the values of distal pressuresare affected by temperature,15,21,27 it is important to mea-sure after the patient rests under a warming blanket toobtain reliable results.

It is unclear why low toe pulse wave amplitude is asso-ciated with lower patient survival and worse prognosis tothe limb. Damping of the pulse waves distal to the site ofobstruction results in a lower amplitude of the waves, sim-ilar to the effect of the obstruction on the pressure val-ues.28,29 However, pulse wave amplitude also depends onskin blood flow16 and may be related to events in themicrocirculation that are brought about by the presence ofsevere ischemia.7,11,30 The presence of low amplitude ofpulse waves recorded during reactive hyperemia was asso-ciated independently with the occurrence of ischemicheart disease and related death.31

All our patients had arterial disease and skin lesionsand thus fit the classification of Fontaine IV and the recentdefinition of critical limb ischemia of the TransAtlanticInter-Society Consensus Group.32 Furthermore, twothirds of the sample consisted of patients with toe pressureof 30 mm Hg or less, which indicates severe obstruc-tion.7,9,18,20 The fate of our patients was generally similarto that in recent findings from vascular surgical centers,which, however, dealt with groups that tended to havemore severe arterial disease, a fewer proportion of patientswith diabetes, and a higher rate (60%-90%) of surgicalintervention compared with 26% in our sample.33-35 Inthe studies from surgical centers after 1 year of follow-up,20% to 32% of patients died, which is similar to the 23% ofour patients. The percentage of patients alive with a majoramputation after 1 year ranged from 21% to 26% in thestudies from surgical centers, compared with 19% in ourseries. The percentage alive without a major amputationwas 58% in our sample compared with a range of 47% to55% in the surgical series. These results on amputation anddeath are similar to other estimates7,32 and also suggestthat although arterial surgery decreases the severity oreliminates arterial obstruction and thus improves progno-sis for the limb, the mortality rate does not appear to bealtered. This is likely due to the fact that patients who havesevere arterial obstruction with skin breakdown and criti-cal limb ischemia represent a group with severe general-ized atherosclerosis with involvement of the vessels thatsupply the vital organs.

JOURNAL OF VASCULAR SURGERY714 Carter and Tate April 2001

The better prognosis in those individuals who have arelatively high pressure and in those with a high waveamplitude despite low pressure (Fig 3) suggests that a con-servative approach to the management may be appropriatein some cases of patients with such hemodynamic indices.Subgroups of such patients who are at relatively lower risksshould be analyzed separately in studies of critical ischemia.On the other hand, the presence of low pressures and lowpulse wave amplitude indicates poor prognosis and sup-ports the need for an early arterial reconstruction.

Our results indicate that recording of toe pulse waves,which can be done rapidly and easily, is of value in theassessment of the prognosis to the life and limb in patientswith skin lesions and peripheral arterial disease. The com-bination of measurements of pressure with that of waveamplitude further improves the determination of the risksto the limb. Importantly, the finding of a high pulse waveamplitude among the limbs with low systolic pressureidentifies patients who have a better prognosis than thosewho have a low wave amplitude.

We thank the technical and secretarial staff of theVascular Laboratory, St Boniface General Hospital, fortheir excellent work.

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31. Hedblad B, Ögren M, Janzon L, Isacsson S-O, Lindell SE. Low pulse-wave amplitude during reactive leg hyperaemia: an independent, earlymarker for ischaemic heart disease and death. Results from the 21-yearfollow-up of the prospective cohort study ‘Men born in 1914’,Malmö, Sweden. J Intern Med 1994;236:161-8.

32. TASC Working Group: Management of Peripheral Arterial Disease.TransAtlantic Inter-Society Consensus. J Vasc Surg 2000:31(suppl):S1-296.

33. Thompson MM, Sayers RD, Varty K, Reid A, London NJM, BellPRF. Chronic critical leg ischaemia must be redefined. Eur J Vasc Surg1993;7:420-6.

34. Sayers RD, Thompson MM, Hartshorne T, Budd JS, Bell PRF.Treatment and outcome of severe lower-limb ischaemia. Br J Surg1994;81:521-3.

35. Vayssariat M, Gouny P, Cheynel C, Gaitz J-P, Baudot N, NussaumeO. Haemodynamics of patients with severe lower limb arterial disease:the critical aspects of critical ischaemia. Eur J Vasc Endovasc Surg1997;14:284-9.

Submitted May 24, 2000; accepted Sep 5, 2000.

APPENDIXLimb amputation by ABI and pulse wave amplitude:product-limit survival estimates

Stratum 1: strata = all patients

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 2660.00821 0.9925 0.00752 0.00530 2 2640.01916 0.9887 0.0113 0.00648 3 2620.02190 0.9849 0.0151 0.00748 4 2610.02738 0.9812 0.0188 0.00835 5 2600.03012 0.9661 0.0339 0.0111 9 2560.03285 0.9623 0.0377 0.0117 10 2550.03833 0.9547 0.0453 0.0128 12 2530.04107 0.9510 0.0490 0.0133 13 2520.04381 0.9434 0.0566 0.0142 15 2500.04654 0.9396 0.0604 0.0146 16 2490.05202 0.9359 0.0641 0.0150 17 2480.06023 0.9321 0.0679 0.0155 18 2450.06297 0.9283 0.0717 0.0159 19 2440.06571 0.9245 0.0755 0.0162 20 2430.07118 0.9168 0.0832 0.0170 22 2400.07666 0.9130 0.0870 0.0173 23 2390.08214 0.9092 0.0908 0.0177 24 2380.09582 0.9015 0.0985 0.0183 26 2340.10130 0.8976 0.1024 0.0187 27 2330.13689 0.8937 0.1063 0.0190 28 2300.15606 0.8898 0.1102 0.0193 29 2280.16153 0.8859 0.1141 0.0196 30 2270.16701 0.8820 0.1180 0.0199 31 2250.17248 0.8781 0.1219 0.0202 32 2240 20534 0.8741 0.1259 0.0205 33 2200.26010 0.8701 0.1299 0.0208 34 2190.27105 0.8662 0.1338 0.0211 35 2180.28747 0.8622 0.1378 0.0213 36 2170.30938 0.8582 0.1418 0.0216 37 2140.34223 0.8541 0.1459 0.0219 38 2100.36413 0.8501 0.1499 0.0222 39 2090.38330 0.8459 0.1541 0.0224 40 2060.38604 0.8418 0.1582 0.0227 41 2050.39973 0.8377 0.1623 0.0230 42 2040.46817 0.8336 0.1664 0.0232 43 2010.48186 0.8294 0.1706 0.0235 44 1980.49829 0.8252 0.1748 0.0237 45 1950.50103 0.8209 0.1791 0.0240 46 1940.54757 0.8124 0.1876 0.0245 48 1910.58042 0.8082 0.1918 0.0247 49 1900.62971 0.8038 0.1962 0.0250 50 1840.68994 0.7994 0.2006 0.0252 51 1810.71184 0.7949 0.2051 0.0255 52 1790.95551 0.7901 0.2099 0.0258 53 1641.02943 0.7853 0.2147 0.0261 54 1621.12252 0.7804 0.2196 0.0264 55 1591.13347 0.7754 0.2246 0.0266 56 1571.15811 0.7705 0.2295 0.0269 57 1561.22930 0.7655 0.2345 0.0272 58 1531.45654 0.7604 0.2396 0.0275 59 1491.61259 0.7553 0.2447 0.0278 60 1471.76318 0.7500 0.2500 0.0281 61 1422.05339 0.7444 0.2556 0.0284 62 1342.10815 0.7389 0.2611 0.0288 63 1332.28337 0.7333 0.2667 0.0291 64 1312.31896 0.7221 0.2779 0.0297 66 1292.45038 0.7163 0.2837 0.0300 67 1252.54346 0.7106 0.2894 0.0303 68 1233.22245 0.7040 0.2960 0.0307 69 1073.24162 0.6974 0.3026 0.0312 70 106

JOURNAL OF VASCULAR SURGERYVolume 33, Number 4 Carter and Tate 1

3.66324 0.6898 0.3102 0.0317 71 913.69062 0.6822 0.3178 0.0323 72 903.75907 0.6746 0.3254 0.0328 73 88

Stratum 2: strata = high ABI, high AMP

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 1120.00821 0.9911 0.00893 0.00889 1 1110.04381 0.9821 0.0179 0.0126 2 1090.04654 0.9731 0.0269 0.0153 3 1080.10130 0.9640 0.0360 0.0177 4 1070.13689 0.9549 0.0451 0.0197 5 1040.58042 0.9450 0.0550 0.0218 6 961.12252 0.9338 0.0662 0.0243 7 831.13347 0.9224 0.0776 0.0265 8 811.22930 0.9110 0.0890 0.0286 9 801.45654 0.8995 0.1005 0.0304 10 782.10815 0.8868 0.1132 0.0325 11 703.66324 0.8704 0.1296 0.0358 12 533.75907 0.8536 0.1464 0.0389 13 51

Stratum 3: strata = high ABI, low AMP

Survival No. No. time Survival Failure SE failed left

0.0000 1.0000 0 0 0 290.30938 0.9615 0.0385 0.0377 1 250.38604 0.9215 0.0785 0.0533 2 230.39973 0.8814 0.1186 0.0643 3 220.50103 0.8373 0.1627 0.0747 4 190.95551 0.7850 0.2150 0.0864 5 151.76318 0.7196 0.2804 0.1010 6 112.05339 0.6542 0.3458 0.1110 7 102.31896 0.5815 0.4185 0.1201 8 82.54346 0.5088 0.4912 0.1252 9 7

Stratum 4: strata = low ABI, high AMP

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 460.03012 0.9783 0.0217 0.0215 1 450.03833 0.9348 0.0652 0.0364 3 430.05202 0.9130 0.0870 0.0415 4 420.09582 0.8913 0.1087 0.0459 5 410.34223 0.8685 0.1315 0.0501 6 380.62971 0.8443 0.1557 0.0542 7 350.71184 0.8202 0.1798 0.0578 8 341.02943 0.7946 0.2054 0.0614 9 311.15811 0.7672 0.2328 0.0651 10 282.28337 0.7352 0.2648 0.0698 11 232.31896 0.7032 0.2968 0.0737 12 22

Stratum 5: strata = low ABI, low AMP

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 790.00821 0.9873 0.0127 0.0126 1 780.01916 0.9747 0.0253 0.0177 2 770.02190 0.9620 0.0380 0.0215 3 760.02738 0.9494 0.0506 0.0247 4 750.03012 0.9114 0.0886 0.0320 7 720.03285 0.8987 0.1013 0.0339 8 71

0.04107 0.8861 0.1139 0.0357 9 700.04381 0.8734 0.1266 0.0374 10 690.06023 0.8604 0.1396 0.0391 11 660.06297 0.8473 0.1527 0.0406 12 650.06571 0.8343 0.1657 0.0420 13 640.07118 0.8078 0.1922 0.0446 15 610.07666 0.7946 0.2054 0.0458 16 600.08214 0.7813 0.2187 0.0469 17 590.09582 0.7679 0.2321 0.0480 18 570.15606 0.7542 0.2458 0.0491 19 550.16153 0.7404 0.2596 0.0501 20 540.16701 0.7267 0.2733 0.0510 21 530.17248 0.7130 0.2870 0.0518 22 520.20534 0.6993 0.3007 0.0526 23 510.26010 0.6856 0.3144 0.0534 24 500.27105 0.6719 0.3281 0.0540 25 490.28747 0.6582 0.3418 0.0546 26 480.36413 0.6442 0.3558 0.0552 27 460.38330 0.6299 0.3701 0.0558 28 440.46817 0.6155 0.3845 0.0564 29 430.48186 0.6012 0.3988 0.0568 30 420.49829 0.5869 0.4131 0.0573 31 410.54757 0.5576 0.4424 0.0580 33 380.68994 0.5429 0.4571 0.0583 34 371.61259 0.5259 0.4741 0.0589 35 312.45038 0.5078 0.4922 0.0596 36 283.22245 0.4847 0.5153 0.0612 37 213.24162 0.4616 0.5384 0.0625 38 203.69062 0.4360 0.5640 0.0641 39 17

ABI, Ankle/brachial index; AMP, pulse wave amplitude.

Total death by TBI and pulse wave amplitude: product-limit survival estimates

Stratum 1: strata = all patients

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 2380.01369 0.9958 0.00420 0.00419 1 2370.03559 0.9916 0.00840 0.00592 2 2360.05476 0.9874 0.0126 0.00723 3 2350.05749 0.9832 0.0168 0.00833 4 2340.06571 0.9790 0.0210 0.00930 5 2330.06845 0.9748 0.0252 0.0102 6 2320.08214 0.9706 0.0294 0.0110 7 2310.09035 0.9664 0.0336 0.0117 8 2300.12594 0.9622 0.0378 0.0124 9 2290.13415 0.9580 0.0420 0.0130 10 2280.13963 0.9538 0.0462 0.0136 11 2270.16153 0.9496 0.0504 0.0142 12 2260.17796 0.9412 0.0588 0.0153 14 2240.18070 0.9370 0.0630 0.0158 15 2230.18891 0.9286 0.0714 0.0167 17 2210.19986 0.9244 0.0756 0.0171 18 2200.29295 0.9202 0.0798 0.0176 19 2190.30664 0.9160 0.0840 0.0180 20 2180.30938 0.9118 0.0882 0.0184 21 2170.32307 0.9076 0.0924 0.0188 22 2160.33402 0.9034 0.0966 0.0192 23 2150.33949 0.8992 0.1008 0.0195 24 2140.36687 0.8950 0.1050 0.0199 25 2130.36961 0.8908 0.1092 0.0202 26 2120.40794 0.8866 0.1134 0.0206 27 2110.41615 0.8824 0.1176 0.0209 28 2100.47912 0.8782 0.1218 0.0212 29 2090.48734 0.8739 0.1261 0.0215 30 2080.50103 0.8697 0.1303 0.0218 31 207

0.53936 0.8655 0.1345 0.0221 32 2060.54483 0.8613 0.1387 0.0224 33 2050.55852 0.8571 0.1429 0.0227 34 2040.58864 0.8529 0.1471 0.0230 35 2030.59685 0.8487 0.1513 0.0232 36 2020.59959 0.8445 0.1555 0.0235 37 2010.62423 0.8403 0.1597 0.0237 38 2000.63244 0.8361 0.1639 0.0240 39 1990.69815 0.8319 0.1681 0.0242 40 1980.70089 0.8277 0.1723 0.0245 41 1970.74196 0.8235 0.1765 0.0247 42 1960.77207 0.8193 0.1807 0.0249 43 1950.79398 0.8151 0.1849 0.0252 44 1940.81862 0.8109 0.1891 0.0254 45 1930.82683 0.8067 0.1933 0.0256 46 1920.84052 0.8025 0.1975 0.0258 47 1910.84326 0.7983 0.2017 0.0260 48 1900.85147 0.7941 0.2059 0.0262 49 1890.85421 0.7899 0.2101 0.0264 50 1880.86516 0.7857 0.2143 0.0266 51 1870.88433 0.7773 0.2227 0.0270 53 1850.97194 0.7731 0.2269 0.0271 54 1840.97741 0.7689 0.2311 0.0273 55 1831.07050 0.7605 0.2395 0.0277 57 1801.07598 0.7562 0.2438 0.0278 58 1791.09514 0.7520 0.2480 0.0280 59 1781.10609 0.7478 0.2522 0.0282 60 1771.12526 0.7436 0.2564 0.0283 61 1761.18275 0.7393 0.2607 0.0285 62 1751.19097 0.7351 0.2649 0.0286 63 1741.32786 0.7309 0.2691 0.0288 64 1731.35250 0.7267 0.2733 0.0289 65 1721.39083 0.7224 0.2776 0.0290 66 1711.39630 0.7182 0.2818 0.0292 67 1701.58795 0.7140 0.2860 0.0293 68 1691.66188 0.7098 0.2902 0.0294 69 1681.68104 0.7055 0.2945 0.0296 70 1671.70568 0.7013 0.2987 0.0297 71 1661.71389 0.6971 0.3029 0.0298 72 1651.75770 0.6886 0.3114 0.0300 74 1621.81793 0.6843 0.3157 0.0302 75 1611.89185 0.6801 0.3199 0.0303 76 1601.90007 0.6758 0.3242 0.0304 77 1591.93566 0.6716 0.3284 0.0305 78 1581.94935 0.6673 0.3327 0.0306 79 1571.97125 0.6631 0.3369 0.0307 80 1561.97947 0.6588 0.3412 0.0308 81 1552.01506 0.6546 0.3454 0.0309 82 1542.05613 0.6503 0.3497 0.0310 83 1532.14100 0.6461 0.3539 0.0311 84 1522.18754 0.6418 0.3582 0.0311 85 1512.26694 0.6376 0.3624 0.0312 86 1502.29979 0.6333 0.3667 0.0313 87 1492.31348 0.6291 0.3709 0.0314 88 1482.36550 0.6248 0.3752 0.0315 89 1472.37919 0.6206 0.3794 0.0315 90 1462.39836 0.6163 0.3837 0.0316 91 1452.40931 0.6121 0.3879 0.0317 92 1442.46133 0.6078 0.3922 0.0317 93 1432.46680 0.6036 0.3964 0.0318 94 1422.48049 0.5993 0.4007 0.0318 95 1412.54346 0.5951 0.4049 0.0319 96 1402.55168 0.5908 0.4092 0.0320 97 1392.63655 0.5866 0.4134 0.0320 98 1382.65298 0.5823 0.4177 0.0321 99 1372.65845 0.5781 0.4219 0.0321 100 1362.66393 0.5738 0.4262 0.0321 101 1352.68036 0.5696 0.4304 0.0322 102 1342.72416 0.5653 0.4347 0.0322 103 1332.78166 0.5611 0.4389 0.0323 104 1322.80356 0.5568 0.4432 0.0323 105 131

JOURNAL OF VASCULAR SURGERY2 Carter and Tate April 2001

2.84189 0.5526 0.4474 0.0323 106 1302.88296 0.5483 0.4517 0.0324 107 1292.94045 0.5441 0.4559 0.0324 108 1283.01711 0.5398 0.4602 0.0324 109 1273.01985 0.5356 0.4644 0.0324 110 1263.08008 0.5313 0.4687 0.0325 111 1253.11020 0.5271 0.4729 0.0325 112 1243.11841 0.5228 0.4772 0.0325 113 1233.14031 0.5186 0.4814 0.0325 114 1223.28268 0.5143 0.4857 0.0325 115 1213.28816 0.5058 0.4942 0.0325 117 1193.30185 0.5016 0.4984 0.0325 118 1183.40041 0.4929 0.5071 0.0325 120 1143.44148 0.4886 0.5114 0.0325 121 1133.44422 0.4843 0.5157 0.0325 122 1123.52635 0.4799 0.5201 0.0325 123 1103.54552 0.4755 0.5245 0.0325 124 1093.57563 0.4712 0.5288 0.0325 125 1083.65503 0.4667 0.5333 0.0325 126 1053.80287 0.4622 0.5378 0.0325 127 1033.80561 0.4578 0.5422 0.0325 128 1024.09035 0.4529 0.5471 0.0325 129 944.09582 0.4481 0.5519 0.0325 130 934.10404 0.4384 0.5616 0.0325 132 904.11225 0.4334 0.5666 0.0326 133 874.12594 0.4284 0.5716 0.0326 134 864.26283 0.4231 0.5769 0.0326 135 794.27926 0.4176 0.5824 0.0326 136 774.35592 0.4120 0.5880 0.0327 137 734.36140 0.4063 0.5937 0.0327 138 724.39699 0.4007 0.5993 0.0327 139 714.49829 0.3950 0.6050 0.0328 140 694.52019 0.3893 0.6107 0.0328 141 684.70910 0.3829 0.6171 0.0329 142 604.79398 0.3764 0.6236 0.0329 143 584.81588 0.3697 0.6303 0.0330 144 554.86242 0.3629 0.6371 0.0331 145 545.02669 0.3557 0.6443 0.0332 146 495.11978 0.3484 0.6516 0.0333 147 485.32512 0.3410 0.6590 0.0334 148 465.35250 0.3334 0.6666 0.0335 149 445.37714 0.3259 0.6741 0.0336 150 435.67283 0.3175 0.6825 0.0338 151 386.00137 0.3066 0.6934 0.0343 152 286.16016 0.2938 0.7062 0.0352 153 236.17112 0.2810 0.7190 0.0359 154 226.27515 0.2662 0.7338 0.0370 155 186.46133 0.2472 0.7528 0.0389 156 136.91034 0.2197 0.7803 0.0432 157 86.95962 0.1923 0.8077 0.0457 158 7

Stratum 2: strata = high TBI, high AMP

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 1100.01369 0.9909 0.00909 0.00905 1 1090.12594 0.9818 0.0182 0.0127 2 1080.13415 0.9727 0.0273 0.0155 3 1070.16153 0.9636 0.0364 0.0178 4 1060.17796 0.9545 0.0455 0.0199 5 1050.29295 0.9455 0.0545 0.0217 6 1040.36687 0.9364 0.0636 0.0233 7 1030.41615 0.9273 0.0727 0.0248 8 1020.48734 0.9182 0.0818 0.0261 9 1010.58864 0.9091 0.0909 0.0274 10 1000.59685 0.9000 0.1000 0.0286 11 990.59959 0.8909 0.1091 0.0297 12 980.62423 0.8818 0.1182 0.0308 13 97

JOURNAL OF VASCULAR SURGERYVolume 33, Number 4 Carter and Tate 3

0.70089 0.8727 0.1273 0.0318 14 960.81862 0.8636 0.1364 0.0327 15 950.85147 0.8545 0.1455 0.0336 16 940.85421 0.8455 0.1545 0.0345 17 930.86516 0.8364 0.1636 0.0353 18 920.88433 0.8273 0.1727 0.0360 19 911.07050 0.8091 0.1909 0.0375 21 891.07598 0.8000 0.2000 0.0381 22 881.10609 0.7909 0.2091 0.0388 23 871.12526 0.7818 0.2182 0.0394 24 861.39083 0.7727 0.2273 0.0400 25 851.58795 0.7636 0.2364 0.0405 26 841.71389 0.7545 0.2455 0.0410 27 831.75770 0.7455 0.2545 0.0415 28 821.89185 0.7364 0.2636 0.0420 29 811.90007 0.7273 0.2727 0.0425 30 801.97125 0.7182 0.2818 0.0429 31 791.97947 0.7091 0.2909 0.0433 32 782.36550 0.7000 0.3000 0.0437 33 772.37919 0.6909 0.3091 0.0441 34 762.39836 0.6818 0.3182 0.0444 35 752.54346 0.6727 0.3273 0.0447 36 742.78166 0.6636 0.3364 0.0450 37 732.88296 0.6545 0.3455 0.0453 38 722.94045 0.6455 0.3545 0.0456 39 713.01985 0.6364 0.3636 0.0459 40 703.08008 0.6273 0.3727 0.0461 41 693.14031 0.6182 0.3818 0.0463 42 683.30185 0.6091 0.3909 0.0465 43 673.44148 0.5999 0.4001 0.0467 44 653.52635 0.5906 0.4094 0.0469 45 643.57563 0.5814 0.4186 0.0471 46 633.65503 0.5719 0.4281 0.0473 47 603.80287 0.5622 0.4378 0.0474 48 583.80561 0.5525 0.4475 0.0476 49 574.09582 0.5417 0.4583 0.0479 50 504.10404 0.5308 0.4692 0.0481 51 494.27926 0.5193 0.4807 0.0485 52 454.39699 0.5069 0.4931 0.0489 53 414.52019 0.4942 0.5058 0.0492 54 394.70910 0.4801 0.5199 0.0498 55 344.79398 0.4660 0.5340 0.0503 56 334.81588 0.4510 0.5490 0.0509 57 304.86242 0.4359 0.5641 0.0514 58 295.11978 0.4198 0.5802 0.0519 59 265.35250 0.4030 0.5970 0.0525 60 245.37714 0.3862 0.6138 0.0529 61 236.17112 0.3565 0.6435 0.0566 62 126.46133 0.3119 0.6881 0.0647 63 76.91034 0.2340 0.7660 0.0832 64 3

Stratum 3: strata = high TBI, low AMP

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 280.17796 0.9643 0.0357 0.0351 1 270.18070 0.9286 0.0714 0.0487 2 260.19986 0.8929 0.1071 0.0585 3 250.47912 0.8571 0.1429 0.0661 4 240.63244 0.8214 0.1786 0.0724 5 230.74196 0.7857 0.2143 0.0775 6 220.82683 0.7500 0.2500 0.0818 7 210.88433 0.7143 0.2857 0.0854 8 200.97741 0.6786 0.3214 0.0883 9 191.35250 0.6429 0.3571 0.0906 10 181.66188 0.6071 0.3929 0.0923 11 171.75770 0.5692 0.4308 0.0940 12 152.14100 0.5313 0.4687 0.0951 13 14

2.26694 0.4933 0.5067 0.0956 14 132.46133 0.4554 0.5446 0.0955 15 123.01711 0.4174 0.5826 0.0947 16 113.11020 0.3795 0.6205 0.0934 17 105.02669 0.3253 0.6747 0.0945 18 65.67283 0.2439 0.7561 0.0999 19 3

Stratum 4: strata = low TBI, high AMP

Survival No. No.time Survival Failure SE failed left

0.00000 1.0000 0 0 0 250.18891 0.9600 0.0400 0.0392 1 240.30938 0.9200 0.0800 0.0543 2 230.33949 0.8800 0.1200 0.0650 3 220.97194 0.8400 0.1600 0.0733 4 211.18275 0.8000 0.2000 0.0800 5 201.32786 0.7600 0.2400 0.0854 6 191.93566 0.7200 0.2800 0.0898 7 182.29979 0.6800 0.3200 0.0933 8 172.65845 0.6400 0.3600 0.0960 9 162.84189 0.6000 0.4000 0.0980 10 153.28816 0.5600 0.4400 0.0993 11 143.44422 0.5200 0.4800 0.0999 12 134.09035 0.4800 0.5200 0.0999 13 124.11225 0.4364 0.5636 0.0999 14 104.12594 0.3927 0.6073 0.0990 15 94.35592 0.3491 0.6509 0.0971 16 84.49829 0.3055 0.6945 0.0943 17 7

Stratum 5: strata = low TBI, low AMP

Survival No. No. time Survival Failure SE failed left

0.00000 1.0000 0 0 0 750.03559 0.9867 0.0133 0.0132 1 740.05476 0.9733 0.0267 0.0186 2 730.05749 0.9600 0.0400 0.0226 3 720.06571 0.9467 0.0533 0.0259 4 710.06845 0.9333 0.0667 0.0288 5 700.08214 0.9200 0.0800 0.0313 6 690.09035 0.9067 0.0933 0.0336 7 680.13963 0.8933 0.1067 0.0356 8 670.18891 0.8800 0.1200 0.0375 9 660.30664 0.8667 0.1333 0.0393 10 650.32307 0.8533 0.1467 0.0409 11 64

0.33402 0.8400 0.1600 0.0423 12 630.36961 0.8267 0.1733 0.0437 13 620.40794 0.8133 0.1867 0.0450 14 610.50103 0.8000 0.2000 0.0462 15 600.53936 0.7867 0.2133 0.0473 16 590.54483 0.7733 0.2267 0.0483 17 580.55852 0.7600 0.2400 0.0493 18 570.69815 0.7467 0.2533 0.0502 19 560.77207 0.7333 0.2667 0.0511 20 550.79398 0.7200 0.2800 0.0518 21 540.84052 0.7067 0.2933 0.0526 22 530.84326 0.6933 0.3067 0.0532 23 521.09514 0.6797 0.3203 0.0539 24 501.19097 0.6661 0.3339 0.0545 25 491.39630 0.6525 0.3475 0.0551 26 481.68104 0.6390 0.3610 0.0556 27 471.70568 0.6254 0.3746 0.0560 28 461.81793 0.6118 0.3882 0.0564 29 451.94935 0.5982 0.4018 0.0568 30 442.01506 0.5846 0.4154 0.0571 31 432.05613 0.5710 0.4290 0.0574 32 422.18754 0.5574 0.4426 0.0576 33 412.31348 0.5438 0.4562 0.0578 34 402.40931 0.5302 0.4698 0.0579 35 392.46680 0.5166 0.4834 0.0580 36 382.48049 0.5030 0.4970 0.0580 37 372.55168 0.4894 0.5106 0.0580 38 362.63655 0.4758 0.5242 0.0580 39 352.65298 0.4622 0.5378 0.0579 40 342.66393 0.4486 0.5514 0.0578 41 332.68036 0.4350 0.5650 0.0576 42 322.72416 0.4214 0.5786 0.0574 43 312.80356 0.4078 0.5922 0.0571 44 303.11841 0.3942 0.6058 0.0568 45 293.28268 0.3807 0.6193 0.0565 46 283.28816 0.3671 0.6329 0.0561 47 273.40041 0.3388 0.6612 0.0552 49 243.54552 0.3241 0.6759 0.0547 50 224.10404 0.3087 0.6913 0.0542 51 204.26283 0.2894 0.7106 0.0542 52 154.36140 0.2701 0.7299 0.0539 53 145.32512 0.2493 0.7507 0.0536 54 126.00137 0.2266 0.7734 0.0533 55 106.16016 0.1983 0.8017 0.0536 56 76.27515 0.1653 0.8347 0.0539 57 56.95962 0.1239 0.8761 0.0540 58 3

AMP, Pulse wave amplitude; TBI, toe/brachial index.

JOURNAL OF VASCULAR SURGERY4 Carter and Tate April 2001