Improved Patient Selection for Angioplasty Utilizing Color Doppler Imaging

Paul Collier, MD, Geoffrey Wilcox, MD, Daniel Brooks, MD, Susan Laffey, RVT, Thomas Dalton, RVT, Scwick|ey, Pennsylvania

The accepted approach to patients with intermittent calf claudication is nonoperative unless the symp- toms are truly incapacitating, in which ease arteri- ography and either percutaneous angioplasty or op- eration is indicated. Arteriography is considered a preoperative procedure. However, with improve- ments in percutaneous angioplasty, we have altered our approach to those patients with limiting, but not incapacitating, claudication. These patients are given the choice of conservative treatment or percu- taneous angioplasty, but not operation. In an at- tempt to limit arteriography to only those patients who would benefit f rom angioplasty, we have em- ployed color Doppler imaging as a screening tech- nique. Over a 2-year period, 62 patients with limit- ing claudication were evaluated with color Doppler imaging. Thirty-six patients had long occlusions and did not undergo arteriography since they were not believed to be candidates for percutaneous an- gioplasty. Three short (less than 5 cm) occlusions and 23 localized stenoses were identifeid in the su- perficial femoral and popliteal arteries. Angiogra- phy confirmed the Doppler findings in all 26 cases. In 24 patients, dilatation was successful, whereas 2 patients' arteries could not be dilated. Two stenoses recurred early and were redilated. There were no complications from the angioplasties. We conclude that in the subset of patients with limiting, but not incapacitating, claudication, color Doppler imaging can accurately select those patients who will benefit from angioplasty. In this way, patients can be spared unnecessary angiograms.

A lthough patients are inconvenienced by the develop- ment of moderately severe intermittent claudica- tion, nondiabetics are at little risk to lose their leg in this situation. Untreated, the majority of such patients will remain symptomatically stable for 5 years after the devel- opment of their symptoms. Approximately 5% will ulti- mately need extremity amputation. The recommended

From the Department of Surgery, Sewicldey Valley Hospital, Sewick- Icy, Pennsylvania.

Requests for reprints should be addressed to Paul E. Collier, MD, Suite 200, 301 Ohio River Boulevard, Sewickley, Pennsylvania 15143.

Presented at the 18th Annual Meeting of the Society for Clinical Vascular Surgery, Palm Desert, California, March 7-11, 1990.

treatment for intermittent claudication has been very conservative, consisting of abstinence from tobacco prod- ucts, regular exercise, control of associated medical dis- eases, and, recently, therapy with pcntoxifylline. There are two reasons for this conservative treatment approach. First, all patients have required arteriograms to deter- mine what procedure could be done for them. Artefiogra- phy is expensive, invasive, and has the potential for com- plications. Second, operative treatment consists of bypass grafting, the results of which have not been perfected. Many times when the bypass eventually fails, the pa- tient's leg is at more risk of gangrene than if no operative treatment had been undertaken originally. Traditional teaching has reserved the option of a bypass graft for those situations in which claudication precluded gainful employment or imposed an unacceptable alteration in lifestyle.

Three changes have occurred that made us question the traditional approach to the treatment of intermittent claudication. Lifestyle issues have become much more important to patients, especially after they retire. Patients arc extremely knowledgeable about medical advances and arc much less willing to agree to conservative treat- mcnt when a simple alternative exists. Second, newer treatment modalities, such as balloon angioplasty, laser angioplasty, and pcrcutancous athrectomy, have bccn de- veloped. These procedures have expanded the therapeutic options for patients who desire symptomatic relief with- out surgery. The results are often comparable to those of operation, but with much lower risk. Finally, newer diag- nostic studies have become available to assess the arterial anatomy without arteriography [I].

In an attempt to determine if patients with limiting claudication could be selected for pcrcutaneous balloon angioplasty without having to undergo screening arteri- ography, wc prospectively studied patients with color Doppler imaging (Quantum QAD I Scanner, Quantum Medical Systems, Issaquah, WA). If the patient was believed to be a suitable candidate, arteriography was performed and angioplasty attempted. The results of this study are analyzed in this article to determine whether a new approach to intermittent claudication is appropriate.

PATIENTS AND METHODS Sixty-two patients with normal femoral pulses and no

palpable or extremely weak popliteal or distal pulses were evaluated with color Doppler imaging. All examinations were performed with both 5- and 7.5-MHz linear array probes. The external lilac, common femoral, superficial femoral, deep femoral, popliteal, posterior tibial, anterior tibial, and pcroneal arteries were examined in their en- tirety. Decreased color saturation (i.e., increased "white- ncss") occurs in areas of increased velocity. Decreased

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Figure 1. Color Doppler image of the superficial femoral artery. Decreased luminal diameter and decreased color saturation are evident in the 90+ % stenosis. The velocity accelerates from 65 cm/second before the stenosis to 359 cm/second within the stenosis. Marked turbulence in the form of a multicolored visible bruit is evident just beyond the stenosis.

luminal diameters were generally found in these areas. Doppler velocity measurements were taken before and after the area of suspected stenosis and within the steno- sis. The Doppler spectrum was also obtained in these regions. Random velocities and spectra were also ob- tained in all of the aforementioned arteries. The ratio of the peak systolic velocity within the stenosis to the veloci- ty in the artery proximal to the stenosis was used to determine the degree of stenosis. A twofold increase in velocity represented a 50% stenosis. Higher ratios repre- sented tighter stenoses. Exact numeric values were not attributed to the stenoses once hemodynamic significance was achieved, although a "feeling" for the degree of ste- nosis was developed (Figure 1). In occluded arteries, no color flow was detected. The length of the occlusion was measured. Drawings were made of the arterial tree from the color flow images.

Twenty-six patients were believed to be appropriate candidates for percutaneous angioplasty. These patients all underwent arteriography. The arteriograms were then compared with the composite pictures made from the color images. Six patients who were not candidates for angioplasty also underwent arteriography. That provided 32 femoral and 32 popliteal segments and 96 tibial and peroneal arteries for comparison.

RESULTS Twenty-six of the 62 patients evaluated with color

Doppler imaging were believed to be suitable candidates for percutaneous balloon angioplasty. These patients all underwent arteriography. Three patients had occlusions of 5 cm or less on scanning. Two of these were identical to the arteriographic findings, while the arteriogram showed the other occlusion to be 9 cm compared with a 4- cm occlusion on scanning. At the time of angioplasty, the radiologist believed that the occlusion was closer to 4 cm in length. He expressed his belief that the segment just distal to the occlusion was being filled with non-opacified blood from a collateral. After the angioplasty, this branch was seen to fill from a normal segment. All 23 hemody- namically significant stenoses in the superficial femoral and popliteat arteries were confirmed at the time of angi- oplasty. Ten of these lesions were in the area of the adductor canal. The velocity ratio correlated with the degree of stenosis found on the angiogram, i.e., the higher the ratio, the tighter the stenosis.

In 24 patients, balloon angioplasty was successful. Two lesions were too tortuous and too tight for the radiol- ogist to negotiate a guidewire through. These two lesions had velocity ratios of 8:1 and 6:1. Two of the lesions in which successful angioplasty was performed recurred,

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COLOR DOPPLER IMAGING FOR ANGIOPLASTY SELECTION

one at 4 months and the other at 6 months. These were both successfully redilated. There were no deaths or ma- jor complications from the percutaneous angioplasties. All successful angioplasties relieved the patient's symp- toms. Two patients developed minor hematomas that did not require treatment.

Six of the 36 patients who did not qualify for angio- plasty underwent arteriography and bypass grafting. Four patients had a perfect match between their scan and arteriogram. One scan showed a popliteal artery that reconstituted above the knee and was thought to be an acceptable artery; however, the operating surgeon be- lieved that the artery was too irregular on the angiogram and elected to place the bypass to the more normal- appearing below-knee segment. One patient's arterio- gram showed only a patent posterior tibial artery being filled by a large collateral. Color Doppler imaging showed a patent popliteal artery below the knee and two- vessel runoff through the posterior tibial and peroneal arteries. It was elected to expose the popliteal artery and perform an intraoperative arteriogram. This confu'med the findings of the scan. A bypass graft was successfully placed to the popliteal artery below the knee.

When we originally began scanning the lower extrem- ities, it would take the technicians between 60 to 90 minutes to evaluate one limb. As their experience in- creased, the scanning time for each extremity has de- creased to 30 minutes on average. The peroneal artery is the most difficult to scan. By using the posterior approach with the medial edge of the fibula as a guide, the peroneal artery can be visualized with color Doppler imaging in all but the most obese patients [2]. Since this study only included patients with claudication, the tibial vessels were either normal or totally occluded, unlike diabetics' distal occlusive disease. The scanner again had near-perfect correlation with the arteriograms. Of the 96 tibial and peroneal vessels evaluated in the 32 patients, who also underwent arteriography, 93 correlated perfectly. One patient was found to have a patent peroneal artery that was missed on the angiogram but found on the intraoper- ative angiogram. One obese patient's peroneal artery could not be seen on the scan, and one focal occlusion of an anterior tibial artery was missed by color Doppler imaging.

Therefore, color Doppler imaging provided identical information to that of the arteriogram in 62 of 64 (97%) femoral and popliteal segments evaluated. In the other two segments, the scanner was believed to be more accu- rate in one and the arteriogram more accurate in the other. The scanner and arteriography again agreed in 97% (93 of 96) of the tibial and peroneal arteries evaluat- ed. If only arteriography had been performed on these patients, one patient would have been denied relief be- cause only patent popliteal and peroneal arteries were seen on the scan.

COMMENTS With the rapid expansion of interventional vascular

techniques, numerous patients who were not considered surgical candidates in the past are now being offered

these options to improve their circulation. Unfortunately, the selection process has not kept pace with the techno- logic progress. Most patients required arteriograms to determine if, indeed, they were truly candidates for inter- vention. Arteriography has always been considered the gold standard for vascular diagnosis. Our results chal- lenge this premise. Color Doppler imaging is as accurate as arteriography in providing anatomic information about the arterial tree and surpasses arteriography by providing accurate physiologic information. Once it is believed that a patient's symptoms may warrant interven- tion, the vascular physician must determine the location, the severity, and the length of the occlusive process to decide what procedure is best suited to the patient. Pulse examination and segmental Doppler pressures are help- ful, but more exact data are deafly required. Color Dopp- ler imaging accurately determined the presence or ab- sence of atherosclerotic plaque in the femoral, popliteal, and tibial vessels. Because the deep 3.5-MHz probe has not been perfected yet, scanning of the aortoiliac seg- ments is not accurate at the present time. Grey scale duplex scanners have accurately assessed the carotid cir- culation [3] and been used in the follow-up of bypass grafts [4]. The addition of color has turned the difficult task of following lower extremity arteries down the leg into a relatively easy process. Even the difficult-to-scan tibioperoneal truck and peroneal artery can be scanned with the color scanner. This study demonstrated that when the scan demonstrates a normal artery, the angio- gram also shows a normal artery. The scan accurately determined the location of disease in all but 2 of the 160 arterial segments evaluated (99%).

Angiographically, severity is rated as either total oc- clusion or as a percentage of stenosis. Because of the eccentric nature of plaque, radiologists often do not agree on the exact percentages when one radiologist is com- pared with another [5]. The scanner and arteriograms agreed on whether an artery was occluded or stenotic in all cases. Probably the most important piece of informa- tion that color Doppler imaging provides, that the angio- gram cannot, is the physiologic importance of the steno- sis. A doubl ing of veloci ty is indicat ive of a hemodynamically significant (50%) stenosis. As the ratio of the velocity within the stenosis to the velocity in the artery before the stenosis increases, so does the degree of severity and therefore the functional significance of the stenosis. This information is not provided by arteriogra- phy.

The length of the occlusive process is also important in determining what new technology is applicable to the patient's problem. Although limited by the small number of total occlusions, our study showed that in one of three total occlusions, the arteriogram overestimated the length of the obstruction. Other studies have also demonstrated this phenomenon [6]. It has been believed that failure to opacify an arterial segment may be due to timing or flow and pressure variables. Color Doppler imaging probably will prove to be a more accurate way to assess the exact length of an occlusion than arteriography.

We conclude that color Doppler imaging is an accu-

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rate noninvasive means to assess the femoral, popliteal, and tibial vessels for stenosis or occlusion. The addition of color-flow imaging to the duplex scan makes it possible to accurately assess the tibial and peroneal arteries. Color Doppler imaging is an accurate screen to determine if a patient qualifies for percutaneous angioplasty. As more experience and confidence are gained, it should be possi- ble in the near future to perform infrainguinal bypasses without employing preoperative arteriography.

REFERENCES 1. Jager KA, Philips D J, Martin RL, et al. Noninvasive mapping of lower limb arterial lesions. Ultrasound Med Biol 1985; 11: 515-21. 2. Collier PE, Aster E, Veith F J, Gupta SK, Nunez A. Acute thrombosis of arterial grafts. In: Bergan J J, Yas JST, eds. Vascular surgery emergencies. New York: Grune & Stratton, 1987. 3. Thomas GI, Jones TW, Stavney LS, et al. Carotid endartectomy after Doppler ultrasonographie examination without angiography. Am J Surg 1984; 151: 616-9. 4. Bandyk DF, Cato RF, Towne JB. A low flow velocity predicts failure of femoropopliteal and femorotibial bypass grafts. Surgery 1985; 98: 799-806. 5. Chikos PM, Fisher LD, Hirsch JH, Harley JH, Thiele BL, Strandness DE. Observer variability in evaluation of extracranial carotid artery stenosis. Stroke 1983; 14: 885-92. 6. Cossman DV, Ellison JE, Wagner WA, et al. Comparison of contrast arteriography to arterial mapping with color-flow duplex imaging in the lower extremities. J Vase Surg 1989; 10: 522-9.

DISCUSSION J. Dennis Baker (LOS Angeles, CA): Dr. Collier and

his associates have added to the documentation of the potential of duplex scanning to screen patients for angio- plasty. I am concerned by the suggestion in the paper that we should change the role of conservative management for the patient with claudication because "patients are less willing to agree to conservative treatment." Despite the availability of balloon dilation as a "nonoperative" method, I remain convinced that all patients with claudi- cation deserve an initial trial with exercise, weight con- trol, and tobacco cessation, rather than going directly to endovascular intervention. It must be remembered that the condition of some patients will be made worse by angioplasty.

I have several specific questions. Patients were select- ed based on a physical examination demonstrating nor- mal femoral pulses. Were there any patients in whom the angiogram showed that the physical findings failed to detect significant inflow disease? You mention that the arterial tree was examined in its entirety from the exter- nal iliac to the tibial branches. Many laboratories have reported difficulty following the superficial femoral ar- tery across the adductor canal. Did you have any proh-

lems in this area? Do you have any suggestions for this part of the examination? In this study, you classified stenoses into those above or below a 50% diameter reduc- tion. Given your results, do you think there is any value in identifying very tight lesions (e.g., having categories of 50% to 80% and 80% to 99% stenoses)? Have you tried to categorize the stenoses based upon image characteristics in an attempt to predict which arterial lesions might respond more or less favorably to endovascular interven- tion?

Tim Cusack (Iowa City, IA): Our group has noted that if there is more than one lesion, e.g., sequential lesions in the superficial femoral artery, then velocity alterations by the first lesion may mask the significance of the second lesion. This could result in failure to detect the second lesion. What is your experience with multiple lesions?

Paul Collier (closing): I agree with Dr. Baker's con- servative approach and attempt to convince patients to try these measures. Often, however, patients want a more interventional approach because claudication limits their lifestyle. In assessing the inflow, we used pulse volume recordings and listened to the femorals for bruits. Outside of some minor irregularities, our findings in the iliac arteries were not unexpected. We did attempt to limit ourselves to a very select group of patients, a focused group.

It is easier to visualize the femoral artery and the adductor canal with color Doppler imaging, especially with the Quantum scanner. It is easier to get deeper into these areas with color Doppler. It also depends upon the experience of the technologists. As for any suggestions I might have, it is important to put the patient in different positions so that the vessel can be visualized from differ- ent angles.

We did try to define hemodynamically significant le- sions, but in such a small patient population, it is difficult to separate them into different categories. There is just not a great enough volume. As for the image characteris- tics, the laboratory has only been established for 2 �89 years now and we train the technologists to characterize the lesions. Maybe this is the next step, but we have't gotten that far yet.

Dr. Cusack, yes and no. Most of the group has only had one lesion. We have had two tandem lesions and the first one was high and the other low and we could sepa- rate them. In the other long stenosis, the distal part of the lesion could be underestimated because of the depressed velocity from the proximal portion.

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