Vascular Briefs

Carotid Endarterectomy Benefits Both Sexes

There has been great controversy over the potential benefit of carotid endarterectomy for patients with symptomatic carotid disease. The North American Symptomatic Carotid Endarterectomy Trial (NASCET) was a multicenter study to evaluate the efficacy of carotid endarterectomy (TEA) in both men and women.

Patients 79 years old or less who had a transient ischemic attack, a small stroke, or amaurosis fugax within the prior four months were evaluated with carotid ultrasound and then an arteriogram. If a carotid stenosis of 70% or more was found in the appropriate carotid artery for the symptoms, the patient was randomized to receive either best medical treatment or best medical treatment plus endarterectomy.

In the surgery group the perioperative morbidity and mortality in the first thirty days was 5.8% while in the medically treated group the morbidity mortality was 3.3% over this same time period.

Interestingly in the next 23 months the stroke rate stayed relatively low in the surgical but not the medical group. At the end of two years the TOTAL stroke rate (including perioperative strokes and death) in the surgical group was 9% but in the medically treated group the rate was 27%.

Thus surgery reduced stroke 65% in the first two years in symptomatic patients with a carotid stenosis of 70% or more.

The more severe the stenosis the more surgery benefited the patient. In patients with stenoses of 70-79%, 80-89% and 90-99%, surgery reduced the absolute risk of stroke 12%, 18% and 26 % respectively in the first two years. Although not calculated in the paper, this appears to represent approximately a 72 % stroke reduction in the first two years when surgery is compared to medical treatment in the 90-99% group.

This study was quickly halted because the results were so dramatic in favor of surgery and the investigators felt that they could no longer justify randomizing these symptomatic patients into medical treatment alone.

This study alone is without question responsible for altering the management of symptomatic carotid disease in this country. Because of the importance of this study and its impact it is included here.

For symptomatic patients with lesser carotid stenoses of 30-69%, the answers are not yet in and the study continues.

Barnett et al. NEJM 325(7):445-53, Aug 15,1991.

PVD in Coronary Bypass Patients

In a multicenter study involving 3,003 patients, the Northern New England Cardiovascular Disease Study Group examined the implications of peripheral vascular disease (PVD) in coronary bypass patients. PVD included abdominal aneurysms, carotid disease and lower extremity occlusive disease.

The mortality of coronary artery bypass grafting (CABG) was 2.4 times as high in patients with PVD as compared to those without. However in examining subgroups with PVD it became apparent that most of this increased mortality was in patients with lower extremity disease. Patients with claudication or a history of lower extremity revascularization or amputation had twice the mortality for coronary bypass as those without a lower extremity vascular problem.

In patients without palpable distal pulses, even without symptoms, the mortality of CABG was three times as high as in those with pulses.

Mortality was particularly high for CABG in patients who were having coronary bypass in preparation for vascular surgery (mortality of CABG 25%) and in those with previous amputation for vascular disease (mortality of CABG 43%).

The increase in the mortality of coronary surgery in patients with PVD was predominantly due to heart failure and arrhythmia.

When patients with carotid disease were analyzed, there was no significant increased risk of death from CABG.

Birkmayer et al. J Vasc Surg 21:445,1995. Porter. Yearbook Vascular Surgery 191-93:1996.

Duplex vs. MRA vs. Angiography for Carotid Evaluation

Accurate measurement of stenoses is critical in the management of patients with carotid disease.

In an effort to evaluate the accuracy of the various imaging techniques a prospective blinded study was done with independent observers reading carotid duplex testing (ultrasound), MRA (magnetic resonance angiogram), and digital arteriography. These results were compared to surgically removed specimens.

The least accurate of the three tests in determining the degree of stenosis was the digital subtraction angiogram which was correct 52% of the time whereas ultrasound was correct in 75% of the tests and MRA 76%. In the specimens that had a critically severe stenosis the MRA and ultrasound were correct 95% and 90% respectively whereas the arteriogram was accurate again in only 52% of specimens. This is not surprising in that with arteriography the vessel in usually evaluated in only two planes.

For ultrasound the caveat is that it is very dependent on the skill of the technician. However, as shown here, the results of Duplex and MRA are clearly superior to arteriography in determining the percent stenosis. Also neither of these carry the stroke risk that is associated with carotid arteriography.

In this study, the angiography was digital but, in our opinion, standard (non-digital) angiography has similar problems with precision, especially when the plaque is eccentric. Arteriography should not be the gold standard in quantitating carotid stenoses.

Pan et al. J Vasc Surg 21:82,1995.
Ricotta. Yearbook Vasc Surg 110-11:1996.

Aspirin as an Adjunct for Venous Stasis Therapy

The mainstay for the treatment of venous stasis disease remains compression therapy either with paste boots, compression stockings, or elastic bandages (in order of decreasing effectiveness). Layton et al. in a study from Great Britain recently reported a randomized, double blind trial employing aspirin as an adjunct to the compression therapy. From a table in the paper it appears that the ulcers were very chronic, averaging over 10 years duration. No patient was included if the ulcer was less than 2 cm. in size or if the patient also had lower extremity arterial insufficiency. Patients were given 300 mg of aspirin daily or a placebo and all were treated with compression.

After four months 38% of the aspirin treated patients were healed compared to none in the placebo group. In addition, ulcer size was diminished in 52 % of the aspirin group compared to 26% for those receiving placebo.

Although this study showed aspirin therapy to be of benefit in venous stasis disease, the study was small (twenty patients) and therefore should not be viewed as definitive. Considering the magnitude of the venous stasis problem and the ease with which this therapy can be employed, the overview is presented.

Layton et al. Lancet 344:164-5,1994.
Porter. Yearbook Vasc Surg 427:1996.

Low Molecular Weight Heparin as Therapy

Low molecular weight heparin (LMWH) presently is utilized in this country as prophylaxis to prevent deep venous thrombosis (DVT). However, the mainstay in the therapy of established DVT continues to be the continuous infusion of standard weight heparin supplemented with Coumadin which is continued after hospital discharge. This regime is highly effective in preventing thrombo- embolic complications but it requires hospitalization.

This study addresses the usefulness and safety of LMWH given as an outpatient for the treatment of proven DVT. This was a randomized trial in which 253 patients with DVT were treated with a standard weight heparin in the traditional way i.e. continuous IV heparin in hospital with monitoring of partial thromboplastin times. Another 247 patients received LMWH (enoxaparin) subcutaneously twice a day mostly at home and without monitoring of the heparin. About half of these patients (127/247) were briefly hospitalized and some received standard heparin for an average of 22 hours prior to randomization to the LMWH group. All patients received at least five days of heparin and were started on coumadin on the second day of treatment.

In the 90 days after being randomized 5.3% of the LMWH home treated group and 6.7% (not statistically different) of the standard weight heparin in hospital treated group had symptomatic recurrence of thromboembolism. Major bleeding occurred in 2.0% of the LMWH patients and in 1.2% of the standard heparin group. Again this was not statistically different. The authors conclude "that enoxaparin, a low molecular weight heparin, can be used safely and effectively to treat patients at home" with DVT.

However, at this time LMWH is not approved in the United States for treatment of established DVT but it should be in the near future.

We have had several occasions to treat patients with deep venous thromboses as outpatients with LMWH because they refused hospitalization. All did well.

Levine et al. NEJM 334, No.11:677-681, March 14, 1996

Aortic Disease as a Risk Factor for Recurrent Stroke

331 patients admitted to the hospital with a diagnosis of brain infarction were studied with transesophageal echo (TEE). Aortic plaque thickness was measured and the patients were then monitored for recurrent stroke.

The authors found that the thicker the aortic plaque, the higher was the risk of both recurrent stroke and other vascular events such as retinal occlusion and myocardial infarction. In those patients with the thickest plaques (4mm or greater), the incidence of recurrent stroke was three times as high as in those with lesser plaques and the incidence of other vascular events were also markedly increased.

The authors conclude that the thickness of the aortic disease is a predictor of the risk of recurrent stroke. More controversial is their conclusion that there is a causal relationship between the aortic disease and stroke. Although I do not believe that a causal relationship is definitively established by this study, there is the strong suggestion that aortic disease can cause stroke. This should be considered in patients in whom the etiology of a stroke is unclear. TEE should be considered in these patients.

Amarenco et al. NEJM 334, No.19:1216-1221, May 9, 1996
Porter. Yearbook Vasc Surg 229-230:1997.

Iliac Artery Stenting

Balloon angioplasty is a mainstay in the management of peripheral vascular disease. Clearly the results can be excellent both short and long term if employed in the proper setting. In general, angioplasty is more effective in stenoses rather than occlusions, in shorter rather than longer lesions, and in iliac arteries rather than infrainguinal vessels. However, recurrent stenoses remain a problem and stenting of the artery has been employed in an effort to improve the results of angioplasty. In the peripheral circulation the stenting device is only approved for use in the iliac artery. The results in the superficial femoral artery and below have been less than satisfactory.

In this present study Cambria et al. addressed the issue as to when stenting should be employed as an adjunct to balloon angioplasty of the iliac arteries. Retrospectively they studied a group of patients who had angioplasty of either the common or external iliac artery with or without stenting.

The patency of the common iliac artery procedures was 78% at two years and did not seem to be affected by placing a stent. Also the results in the external iliacs were better in men than women (80% vs. 61%) at two years. In the external iliac system the patency was significantly improved (p>.05) with stenting. The two year patency in the external iliacs was 83% in the stented arteries and 68% when no stent was employed.

In conclusion, the authors recommend stenting as the primary procedure in the external iliac but stenting should be reserved for "complicated" lesions in the common iliac.

This paper provides useful guidelines for the deployment of stents in the iliac arteries but the total number of patients in the study was only 141 and we therefore await confirmation of these results by other larger series.

Cambria et al. Presented at Society for Vascular Surgery Meeting. 1997.

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