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Vascular and Interventional Radiology |
1 From the Department of Diagnostic Radiology, Philipps University Hospital, Baldingerstrasse, Marburg 35033, Germany (H.J.W., R.S., H.A., K.J.K.); and Department of Radiology, University of Wisconsin, Madison (H.J.W.). Received October 23, 2001; revision requested January 14, 2002; final revision received July 2; accepted July 17. Address correspondence to H.J.W. (e-mail: wagnerh@med.uni-marburg.de).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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MATERIALS AND METHODS: Thirty-four patients (17 men, 17 women; mean age, 68.6 years ± 9.8 [SD]) with peripheral arterial occlusive disease (PAOD) (claudication, n = 15; critical ischemia, n = 19) underwent transcutaneous oxygen pressure measurement at the dorsum of the foot 1 day before PTA, during PTA, 1 day after PTA, and 6 weeks after PTA. Measurements were obtained with the patient in the supine and erect sitting positions, as well as after exercise. Thirty-one patients (21 men, 10 women; mean age, 68.5 years ± 9.3) with symptomatic PAOD who were undergoing intraarterial angiography served as the control group.
RESULTS: Mean pressure before PTA was 31.6 mm Hg ± 24 in the supine position, 50.8 mm Hg ± 22 in the sitting position, and 22.2 mm Hg ± 23 after exercise. Immediately after PTA, a significant increase to 34 mm Hg ± 20 in the supine position was noted (P < .05). One day after PTA, pressure was 37.3 mm Hg ± 20 for the supine position and 52 mm Hg ± 20 for the sitting position. Six weeks after treatment, a further significant increase to 43.9 mm Hg ± 19 in the supine position, 61 mm Hg ± 15 in the sitting position, and 44.7 mm Hg ± 24 after exercise was noted (P < .05). In the control group, a significant pressure decrease immediately after and 1 day after angiography was noted (P < .05). Measurements returned to baseline at 6 weeks follow-up.
CONCLUSION: PTA has a positive effect on oxygen supply to the skin in patients with PAOD. Conversely, intraarterial angiography in patients with PAOD deteriorates skin microcirculation temporarily.
© RSNA, 2003
Index terms: Arteries, extremities, 928.128 • Arteries, transluminal angioplasty, 928.128 • Blood, flow dynamics • Contrast media, effects • Oxygen
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Transcutaneous oxygen pressure has been proven to be a valid parameter for measuring oxygen supply to the lower extremities in patients with peripheral arterial occlusive disease (PAOD) (7), and it is a sensitive indicator with which to discriminate the severity of limb ischemia (8,9). Transcutaneous oxygen pressure has been used extensively to predict the success of extremity amputation (10,11) and to assess the effect of attempted revascularization to restore tissue perfusion (3,4).
Conflicting data have been presented for oxygen pressure measurements after PTA. One group found a significant decrease of oxygen pressure immediately after PTA (5), whereas investigators in a more recent trial found a significant increase of oxygen pressure after PTA (6).
The purpose of our prospective controlled trial was to determine the effect of PTA on skin oxygen supply and microcirculation as measured by means of transcutaneous oxygen pressure in patients with symptomatic disabling lower-limb ischemia compared with that in patients who underwent intraarterial angiography for the assessment of symptomatic disabling lower-limb ischemia.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Study Design
Patients were not assigned to one of the two examination groups, but patients referred to our department for PTA or angiography were asked whether they would allow acquisition of additional oxygen pressure measurements. Patients were otherwise treated with our routine standard of care. Ideally, a prospective randomized controlled trial would be the best study design. However, because only patients with symptomatic PAOD could enter the study, and the vast majority required a revascularization procedure because of the severity of limb ischemia, it would have been unethical to exclude a proportion of the patients from endovascular therapy on a random basis. Therefore, we decided to create a control group consisting of patients with symptomatic lower-limb ischemia referred to our department for intraarterial angiography. Patients were enrolled in the PTA and control groups prospectively and consecutively. All patients referred to our department for either PTA or angiography of lower-limb arteries were amenable for study entry. All results have been assessed on an intention-to-treat basis.
The inclusion criterion was chronic symptomatic PAOD with angiographically proven infrarenal stenosis or obstruction amenable for PTA (1). Patients were excluded if they presented with acute limb-threatening ischemia, were noncompliant, could not give or denied informed consent, were referred from outside hospitals, or had participated in other trials, or if oxygen pressure measurements could not be obtained because of technical problems with the probe.
The primary outcome measure was oxygen pressure assessment 1 day after PTA or angiography. Secondary outcome measures were assessment of oxygen pressure 6 weeks after PTA or angiography, ABI 1 day and 6 weeks after intervention, limb salvage 6 weeks after intervention, and survival 6 weeks after intervention.
Risk factors for PAOD, severity of ischemia, location of obstruction, medication, and technical and clinical success of PTA were all assessed according to published guidelines (12). All complications were recorded and categorized according to the recommendations of the Society of Cardiovascular and Interventional Radiology, or SCVIR (12). Additionally, limb salvage and survival rates were used as further safety parameters.
Transcutaneous Oxygen Pressure Measurements
Measurements were obtained in four examinations: 1 day before PTA or angiography, during PTA or angiography, 1 day after PTA or angiography, and 6 weeks after PTA or angiography. All measurements were obtained by one examiner (R.S.). Before each measurement, the electrode was calibrated automatically. To achieve a steady state, patients had to rest at least 20 minutes in the supine position before measurement was started. The technique and validation of transcutaneous oxygen pressure measurements have been described extensively elsewhere (13,14). Briefly, a modified Clark electrode (Transoxode; Hellige, Freiburg, Germany) was fixed with an adhesive ring at the dorsum of the foot. The skin was prepared by shaving (if necessary), stripping with tape, and cleansing with alcohol. The electrode position was marked on the skin to allow identical positioning during the following measurements. After an automated hyperemia period of approximately 5 minutes at 45°C, measurements were obtained with probe heating of 44°C.
During each of the four examination dates, pressure was first measured with the patient in the supine position. Thereafter, pressure was measured with the patient in an erect sitting position. This position allows better macro- and microcirculation because of increased hydrostatic pressure. Finally, measurements were obtained during exercise. For that purpose, the patient was asked to walk on a treadmill (Ergo K1; Woodway, Weil am Rhein, Germany) with a predefined velocity of 2 mph (no incline) until he or she had to stop because of pain in the lower limb. During exercise, measurements were obtained continuously. This allowed depiction of any exercise-induced disturbances of the microcirculation. Patients who were unable to walk on the treadmill (eg, because of contralateral lower-limb amputation or extensive foot ulcers or necrosis) were asked to bend and extend their affected leg ("bicycling") while lying in the supine position until pain in the limb prevented further exercise. These patients were not included in calculation of the walking distance.
During PTA or angiography, pressure was measured with the patient in the supine position. The examination 1 day after PTA or angiography included measurement in the supine and sitting positions, and in the examination 6 weeks after the intervention, measurements were obtained in the supine and sitting positions, as well as during exercise.
At the first examination, each patient also underwent measurement with an electrode in a subclavicular position on the right chest wall. Measurements obtained from the subclavicular probe served as a reference to rule out low systemic oxygen pressure (eg, respiratory insufficiency or chronic cardiac failure).
Additional Tests
Skin temperature at the dorsum of the foot was measured with an analogue mercury contact thermometer during each of the four measurements. The circumference of the lower limb was measured at four predefined locations (thigh, calf, ankle, foot). A score value was calculated from the four measurements (sum of the four circumferences). The pulses of both lower extremities were palpated, and the ABI was determined. All tests were performed by one examiner (R.S.).
Patients
During a 4-month study period, 66 PTAs were performed in 56 patients for treatment of chronic symptomatic PAOD. Six patients were treated twice, and two patients were treated three times. All 56 patients were eligible for enrollment in the study. Twenty-two patients met exclusion criteria (emergency treatment, n = 4; mechanical ventilation, n = 4; consent refused, n = 3; technical problems with the probe, n = 8; referral from other hospitals, n = 3). The remaining 34 patients were entered into the study prospectively and underwent 34 PTAs. This cohort consisted of 17 women and 17 men with a mean age of 68.5 years ± 9.8 (SD).
During the same period, 106 diagnostic intraarterial angiograms were obtained in 96 patients with symptomatic chronic lower-limb ischemia. Ten patients underwent angiography twice. Sixty-five patients met exclusion criteria (emergency treatment, n = 9; mechanical ventilation, n = 11; enrollment in other trials, n = 32; consent refused, n = 2; technical problems with the probe, n = 3; referral from other hospitals, n = 8). The remaining 31 patients were prospectively enrolled in the study and underwent 31 angiographic examinations. This cohort consisted of 10 women and 21 men with a mean age of 68.5 years ± 9.3.
Interventional Procedures
PTA and angiography were performed by two radiologists (H.J.W., H.A.) according to published guidelines (1,15). All patients undergoing PTA were punctured on the ipsilateral limb (ie, retrograde in cases of suprainguinal lesions; antegrade in cases of infrainguinal lesions). The electrode was mounted on the ipsilateral dorsum of the foot. Measurement was started after a 20-minute rest period to achieve steady state. During PTA, all therapeutic measures were documented (eg, arterial puncture, sheath placement, contrast medium injection [iopamidol; Solutrast 300, Byk Gulden, Germany], recanalization, balloon dilation, completion of angiography, and removal of the sheath) and marked on the continuous paper printout of the transcutaneous oxygen pressure measurement.
In patients undergoing angiography, the oxygen probe was mounted on the symptomatic lower limb, and the contralateral common femoral artery was punctured. All diagnostic measures used during angiography were documented, and oxygen pressure was monitored continuously until the sheath was removed.
In both groups, the number of attempted arterial punctures, volume of contrast material, and amount of medication administered during the procedures were documented.
During the follow-up period, all measures used (eg, PTA, surgical revascularization, sympatholysis, limb amputation, drug therapy, walking exercise) that were related to treatment of PAOD were documented.
Statistical Analysis
Both patient cohorts were analyzed with descriptive statistical methods. Results are reported as mean values ± SDs. For comparison of characteristics of both groups, the Fisher exact test was used. To compare quantitative data within one group, the Wilcoxon signed rank test was used. To compare data between the two groups, the Mann-Whitney U test was applied. A P value less than .05 was considered to indicate a significant difference. Analysis was performed with a personal computer by using SPSS for Windows software, version 7.5.2 G (SPSS, Chicago, Ill).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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In one session of attempted PTA, the occlusion could not be recanalized successfully; all other occlusions were recanalized and dilated with a residual stenosis of less than 30%. Therefore, the technical success rate was 97% (33 of 34). The mean stenosis grade of the 16 stenoses (additionally, 29 complete occlusions were treated) was 84% ± 12 before and 15% ± 11 after PTA. All 31 intended angiography sessions were performed successfully (100%).
In the PTA group, a mean of 115 mL ± 38 of nonionic contrast medium (iopamidol) was administered, whereas in the angiography group, the mean dose was 125 mL ± 28 (P > .05; Fisher exact test).
Two complications occurred in the PTA group. One patient had a vasovagal reaction with complete recovery after administration of 0.5 mg of atropine. Another patient developed spasm of the peroneal artery, which subsided after intraarterial application of nitroglycerin. No complications were noted in the control group. Following intervention, two patients in the PTA group developed a hematoma at the puncture site. One necessitated surgical closure of the puncture site, and the other led to a large retroperitoneal hematoma that was surgically evacuated 3 days later. In the angiography group, only smaller groin hematomas were noted. One necessitated monitoring of the patient for a short time. According to the Society of Cardiovascular and Interventional Radiology classification system (12), 11 complications in the PTA group were minor (category 1, n = 6; category 2, n = 5), and two were major (category 4, n = 2). In the angiography group, 13 complications were minor (category 1, n = 12; category 2, n = 1), and no major complications occurred.
Interventions during the Follow-up Period
Since patients in the angiography group experienced symptomatic disabling or limb-threatening ischemia, revascularization procedures had to be performed in the period between angiography and the 6-week follow-up appointment. Nineteen patients underwent PTA. Four were treated in the iliac arterial segment (three with stent insertion), 12 in the femoropopliteal artery region, and three in the infrapopliteal vessels. Six additional patients underwent surgical procedures. Five femoropopliteal bypass grafts were implanted (three distal anastomoses below the knee and two above the knee), and one patient underwent endarterectomy of the femoral bifurcation.
One patient was treated with computed tomography–guided lumbar sympatholysis. Six patients were treated conservatively with oral anticoagulation medication, and walking exercise was recommended.
For interpretation of the 6-week follow-up data, it has to be taken into account that the vast majority of patients in the control group (25 of 31; 81%) had undergone a revascularization procedure. It would have been unethical, however, to preclude these patients with symptomatic disease from therapy.
Transcutaneous Oxygen Pressure Measurements
Transcutaneous oxygen pressure measurements obtained 1 day prior to PTA or angiography (Fig 1 shows an example of an individual pressure measurement) showed abnormally low values in both groups with patients in the supine or sitting positions, as well as after exercise. However, no significant differences between the two groups could be found (Table 2). In the control group, measurements of the thoracic skin with the transducer in a subclavicular position showed normal values (>40 mm Hg) in all patients.
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Six-week follow-up examination results in the PTA patients showed a significant increase in oxygen pressure levels measured in the supine position (mean, 45 mm Hg ± 20; median, 51 mm Hg) compared with the preinterventional measurements (P < .05, Wilcoxon signed rank test) and those in the control group (P < .05, Mann-Whitney U test). In the angiography group, the mean value of 34 mm Hg ± 21 (median, 35 mm Hg) was not significantly changed with regard to the preprocedural value (P > .05, Wilcoxon signed rank test). However, the immediate postprocedural decrease in this group was balanced. Measurements obtained in the sitting position showed a significant increase in the PTA group (mean, 62 mm Hg ± 15; median, 66 mm Hg) compared with the preinterventional measurements (P < .05, Wilcoxon signed rank test) and those in the control group (mean, 52 mm Hg ± 20; median, 55 mm Hg; P < .05, Mann-Whitney U test). Measurements obtained after exercise demonstrated a significant increase in the PTA group (mean, 45 mm Hg ± 23; median, 51 mm Hg) compared with the preinterventional measurements (P < .05, Wilcoxon signed rank test). Furthermore, the postexercise measurements were not decreased compared with those obtained at rest. Prior to PTA, the postexercise measurements showed a significant mean decrease of 9.4 mm Hg ± 17.5 (median, 4 mm Hg).
For a comprehensive review, the results of all measurements are summarized in Table 3.
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ABI.—Baseline ABI in both groups (PTA, 0.59 ± 0.20; angiography, 0.59 ± 0.29) indicated relevant PAOD. Because of successful PTA, the ABI had significantly increased to a mean of 0.82 ± 0.17 the day after intervention (P < .05, Wilcoxon signed rank test) and was significantly higher compared with that in the angiography group (P < .05, Mann-Whitney U test), where the mean of 0.67 ± 0.21 was not significantly changed from the preangiographic ABI (P > .05, Wilcoxon signed rank test). After 6 weeks of follow-up, the mean ABI was not significantly different in either group (PTA, 0.79 ± 0.27; angiography, 0.74 ± 0.28; P > .05, Mann-Whitney U test). However, it has to be taken into account that 25 patients (81%) in the control group underwent endovascular or surgical revascularization in the time between the day after and 6 weeks after angiography.
Limb salvage and survival.—No patient in either group required amputation in the follow-up period.
One patient in the angiography group died 1 week after angiography. The death was not related to angiography.
Clinical Success
Clinical success 6 weeks after PTA or angiography according to the definition and grading system of the Society of Cardiovascular and Interventional Radiology (12) is shown in Table 5. No patient in the PTA group showed clinical deterioration. The status of two patients was unchanged, and the remaining patient showed minor to excellent clinical improvement. For the angiography group, it has to be mentioned again that 81% of the patients underwent revascularization procedures that contributed to the positive clinical effects in most patients in this group.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Bongard and colleagues presented conflicting data (5). They found a mean decrease from 46 mm Hg before to a mean of 40 mm Hg immediately after PTA in 21 patients with successful PTA. A control group of 16 patients who underwent diagnostic arteriography showed no change before (46 mm Hg) or after (46 mm Hg) angiography (5). The reason for these contradictory findings might be that the patient population in the trial of Bongard et al (5) consisted mostly of patients with claudication (20 of 21) with normal measurements at rest. Furthermore, a relatively large amount of ionic iodinated contrast material was used for angiography (200 mL) and for PTA (250 mL).
In contrast, in our study, most patients experienced limb-threatening ischemia. The mean transcutaneous oxygen pressure measurement in our study cohort before PTA or angiography was below the commonly accepted normal value of 40 mm Hg (32 and 29 mm Hg, respectively). Our results showed a significant decrease in the angiography group, which we believe is a direct effect of contrast medium on the microcirculation. Continuous measurement during angiography and PTA demonstrated an immediate and reproducible decrease after each contrast material injection in our patients with preexisting PAOD.
The effects of iodinated contrast material on the microcirculation have been studied. Bach and coworkers (16) found a significant decrease of erythrocyte velocity in ipsilateral nail folds after selective injection of 20 mL of iopromide (370 mg of iodine per milliliter) in the subclavian artery. Franzeck and colleagues (17) compared the effects of a small amount (10 mL) of ionic (ioxaglate) or nonionic (iopromide) iodinated contrast material on pedal transcutaneous oxygen pressure. Thirty seconds after injection of contrast material through a femoral sheath, a nonsignificant decrease in pressure (mean decrease, 1.7 mm Hg) was found with iopromide, whereas a significant decrease of pressure occurred after ioxaglate injection (mean decrease, 10.1 mm Hg). The mean recovery half-time (time required until 50% of the control pressure level was reached again) was 2.2 minutes (17). In a canine model with nondiseased arteries, Nitahara and colleagues (18) directly measured oxygen pressure in the gastrocnemius muscle with use of a polarographic probe. They found a significant decrease of oxygen pressure in muscle from 51 hPa (38.3 mm Hg) to 45 hPa (33.8 mm Hg) after 30 seconds of injection of 0.4 mL per kilogram of body weight of amidotrizoic acid (370 mg of iodine per milliliter) through a femoral sheath. Following injection of 370 mg of iodine per milliliter of iopamidol, the mean oxygen pressure level decreased from 52 hPa (39.0 mm Hg) to 47 hPa (35.3 mm Hg) after a mean of 20 seconds (18). Given this evidence, the conclusion can be drawn that the significant decrease of transcutaneous oxygen pressure in our patients with preexisting PAOD who were undergoing angiography is an adverse effect of the contrast material. This theory is supported by increased levels of oxygen pressure on the day following angiography, when the preprocedural level was reached again. Conversely, with regard to the significant increase of pressure immediately after PTA, because of the inherent effect of contrast material injections, the positive effect on the microcirculation was counterbalanced. This theory is supported by the further increase of oxygen pressure on the day following PTA.
In conclusion, the results of our study show that successful PTA of lower-limb arteries in patients with claudication and limb-threatening ischemia improves not only the macrocirculation, as demonstrated by means of angiographic findings and increase of ABI, but also the microcirculation and skin oxygen supply, as demonstrated by means of an increase of skin oxygen pressure. Our results are of interest with regard to the adverse effect of iodinated contrast material on skin oxygen supply in a patient population with preexisting PAOD. This effect was transient, and the preprocedural pressure levels were reinstated after 24 hours. However, this provides further reasoning for selecting appropriate indications for intraarterial angiography. Patients with already marginal or insufficient tissue perfusion will experience these adverse effects of iodinated contrast media. We would like to emphasize the value of measuring transcutaneous oxygen pressure levels in patients with diabetes mellitus and PAOD. In these patients, ABI measurements are often not reliable because of heavily calcified calf arteries (19).
Our results and those of other studies (4,6) show that transcutaneous oxygen pressure is a reliable parameter with which to assess the severity of PAOD and to monitor success and long-term outcome of endovascular interventions.
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FOOTNOTES |
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Author contributions: Guarantors of integrity of entire study, H.J.W., R.S.; study concepts, H.J.W.; study design, H.J.W., R.S.; literature research, H.J.W., R.S.; clinical studies, H.J.W., R.S., H.A.; data acquisition, H.J.W., R.S., H.A.; data analysis/interpretation, H.J.W., R.S.; statistical analysis, R.S.; manuscript preparation, H.J.W., R.S.; manuscript definition of intellectual content, editing, revision/review, and final version approval, all authors.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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