Jonathan B. Towne

EFFICACY OF CAROTID ENDARTERECTOMY FOR ASYMPTOMATIC CAROTID STENOS IS. THE VETERANS AFFAIRS COOPERATIVE STUDY GROUP

BACKGROUND The efficacy of carotid endarterectomy in patients with asymptomatic carotid stenosis has not been confirmed in randomized clinical trials, despite the widespread use of operative intervention in such patients. METHODS We conducted a multicenter clinical trial at 11 Veterans Affairs medical centers to determine the effect of carotid endarterectomy on the combined incidence of transient ischemic attack, transient monocular blindness, and stroke. We studied 444 men with asymptomatic carotid stenosis shown arteriographically to reduce the diameter of the arterial lumen by 50 percent or more. The patients were randomly assigned to optimal medical treatment including antiplatelet medication (aspirin) plus carotid endarterectomy (the surgical group; 211 patients) or optimal medical treatment alone (the medical group; 233 patients). All the patients at each center were followed independently by a vascular surgeon and a neurologist for a mean of 47.9 months. RESULTS The combined incidence of ipsilateral neurologic events was 8.0 percent in the surgical group and 20.6 percent in the medical group (P < 0.001), giving a relative risk (for the surgical group vs. the medical group) of 0.38 (95 percent confidence interval, 0.22 to 0.67). The incidence of ipsilateral stroke alone was 4.7 percent in the surgical group and 9.4 percent in the medical group. An analysis of stroke and death combined within the first 30 postoperative days showed no significant differences. Nor were there significant differences between groups in an analysis of all strokes and deaths (surgical, 41.2 percent; medical, 44.2 percent; relative risk, 0.92; 95 percent confidence interval, 0.69 to 1.22). Overall mortality, including postoperative deaths, was primarily due to coronary atherosclerosis. CONCLUSIONS Carotid endarterectomy reduced the overall incidence of ipsilateral neurologic events in a selected group of male patients with asymptomatic carotid stenosis. We did not find a significant influence of carotid endarterectomy on the combined incidence of stroke and death, but because of the size of our sample, a modest effect could not be excluded.

Six-year prospective multicenter randomized comparison of autologous saphenous vein and expanded polytetrafluoroethylene grafts in infrainguinal arterial reconstructions

Autologous saphenous vein (ASV) and polytetrafluoroethylene (PTFE) grafts were compared in 845 infrainguinal bypass operations, 485 to the popliteal artery and 360 to infrapopliteal arteries. Life-table primary patency rates for randomized PTFE grafts to the popliteal artery paralleled those for randomized ASV grafts to the same level for 2 years and then became significantly different (4-year patency rate of 68% +/- 8% [SE] for ASV vs. 47% +/- 9% for PTFE, p less than 0.025). Four-year patency differences for randomized above-knee grafts were not statistically significant (61% +/- 12% for ASV vs. 38% +/- 13% for PTFE, p greater than 0.25) but were for randomized below-knee grafts (76% +/- 9% for ASV vs. 54% +/- 11% for PTFE, p less than 0.05). Four-year limb salvage rates after bypasses to the popliteal artery to control critical ischemia did not differ for the two types of randomized grafts (75% +/- 10% for ASV vs. 70% +/- 10% for PTFE, p greater than 0.25). Although primary patency rates for randomized and obligatory PTFE grafts to the popliteal artery were significantly different (p less than 0.025), 4-year limb salvage rates were not (70% +/- 10% vs. 68% +/- 20%, p greater than 0.25). Primary patency rates at 4 years for infrapopliteal bypasses with randomized ASV were significantly better than those with randomized PTFE (49% +/- 10% vs. 12% +/- 7%, p less than 0.001). Limb salvage rates at 3 1/2 years for infrapopliteal bypasses with both randomized grafts (57% +/- 10% for ASV and 61% +/- 10% for PTFE) were better than those for obligatory infrapopliteal PTFE grafts (38% +/- 11%, p less than 0.01). These results fail to support the routine preferential use of PTFE grafts for either femoropopliteal or more distal bypasses. However, this graft may be used preferentially in selected poor-risk patients for femoropopliteal bypasses, particularly those that do not cross the knee. Although every effort should be made to use ASV for infrapopliteal bypasses, a PTFE distal bypass is a better option than a primary major amputation.

Monitoring functional patency of in situ saphenous vein bypasses: The impact of a surveillance protocol and elective revision

Implementation of a protocol that monitored in situ saphenous vein bypass hemodynamics for low-flow states provided insight into the pathophysiologic characteristics and time course of graft failure. From 1981 to 1988, 250 in situ bypasses to popliteal (n = 83) or tibial (n = 167) arteries were performed in 231 patients. Indications for operation included critical limb ischemia in 232 cases (93%), popliteal aneurysm in 11 cases (4%), and disabling claudication in seven cases (3%). Arterial pressure measurements, continuous-wave Doppler spectral analysis, and duplex ultrasonography were used to assess patency, detect hemodynamic changes indicative of graft stenosis, and localize anatomic hemodynamic changes indicative of graft stenosis. Seventy grafts with correctable anatomic lesions (retained venous valves, graft stenosis, arteriovenous fistula, native vessel atherosclerosis) that decreased graft blood flow or ankle arterial pressure or both were identified. Correction of vein conduit or anastomotic lesions comprised 73 (77%) of the 95 revisions performed. Vein-patch angioplasty of a stenosis was the most common secondary operation performed. Graft revision was highest in the perioperative period (10% at 30 days), decreased to 7% per 6-month interval until 18 months, and was 3% per year thereafter. The primary patency rate of grafts not identified to have a correctable lesion was 86% at 4 years, a level similar to the secondary patency of 81% for grafts requiring one or multiple revisions. The surveillance protocol identified grafts with correctable lesions before thrombosis thereby permitting elective revision of patent grafts. Hemodynamic studies confirmed that a frequent mechanism of late failure of grafts was the development of a low-flow state produced by lesions not amenable to revision.

Experience with in situ saphenous vein bypasses during 1981 to 1989: Determinant factors of long-term patency

From 1981 to 1989, 361 consecutive in situ saphenous vein bypasses were performed. Indications for revascularization were critical limb ischemia (n = 335, 93%), popliteal aneurysm (n = 15, 4%), and claudication (n = 11, 3%). Outflow tract was the popliteal artery in 116 (32%) and tibial artery in 245 (68%) of bypasses. At 6 years primary patency was 63% and secondary patency was 81%. During the performance of the in situ bypass procedure, 86 (24%) venous conduits were modified because of a technical failure (n = 49, 13%) or an inadequate vein segment (n = 37, 10%). Secondary patency at 4 years for bypasses requiring modification was 72% compared to 84% for bypasses not modified (p less than 0.05). Atherosclerotic disease of the inflow artery necessitating endarterectomy, patch angioplasty, or replacement lowered primary patency at 3 years (69%) compared to the inflow artery not requiring reconstruction (46%, p less than 0.02). In the follow-up period, 95 (26%) bypasses were revised because of thrombosis or hemodynamic failure. Bypasses requiring revision had a 4-year secondary patency of 68% compared to 88% for bypasses not revised (p less than 0.02). The first 179 cases (1981 to 1985) were compared to the subsequent 182 cases (1986 to 1989). The secondary patency at 3 years for the latter half (92%) compared to the first half (80%) of the experience was significantly improved (p less than 0.02). The secondary patency for bypasses not requiring revision was significantly improved (p less than 0.02) for the latter half (n = 142, 97%) compared to the first half (n = 124, 83%) of the series. Long-term patency with the in situ saphenous vein bypass is dependent on surgical experience, quality of the venous conduit, and atherosclerotic disease of the inflow artery that necessitates reconstruction. Meticulous surgical technique and compulsive bypass surveillance results in superior long-term patency.

Healing of venous ulcers in an ambulatory care program: The roles of chronic venous insufficiency and patient compliance

PURPOSE A nurse-managed/physician-supervised treatment program for venous ulceration was evaluated to determine the influence of venous hemodynamics, comorbidities, patient behavior, and ulcer characteristics on time to healing and time to recurrence. METHODS The clinical course and long-term follow-up of 71 patients with 99 venous ulcers diagnosed between November 1981 and August 1994 were analyzed by a retrospective review of clinic records. Demographic data, severity of venous insufficiency, ulcer characteristics, and patient compliance were studied. Outcome variables were time to complete ulcer healing and time to first recurrence. RESULTS Ninety-one percent of the ulcers healed completely at a median 3.4 months. There were 52 (57%) recurrences at a median 10.4 months. Ulcers on limbs with a venous refill time of 10 seconds or less demonstrated a significantly longer time to complete healing (p < or = 0.03); however, no effect on time to recurrence was observed. Patients who were in strict compliance with the treatment regimen (n = 32) had significantly faster healing (p < or = 0.02) and fewer recurrences (p < or = 0.004) compared with patients who were less compliant (n = 67). CONCLUSIONS Most venous ulcers can be expected to heal when patients are enrolled in a nurse-managed/physician-supervised ambulatory ulcer clinic. Photoplethysmography-derived venous refill time of 10 seconds or less predicted delayed healing. Strict compliance with the treatment protocol significantly decreased the time to healing and prolonged the time to recurrence.

Durability of the in situ saphenous vein arterial bypass: A comparison of primary and secondary patency *

The use of the saphenous vein in situ is associated with unique problems that decrease primary graft patency (patency uninterrupted by revision). During the past 5 years, we have performed 192 in situ saphenous vein bypasses in 182 patients, including 61 to the popliteal artery, 128 to infrapopliteal arteries, and three to isolated popliteal artery segments. The operative indications were critical limb ischemia in 178 cases (93%), popliteal aneurysm in eight cases (4%), and disabling claudication in six cases (3%). A progressive decline in primary patency occurred after operation. The primary patency rate at 36 months was only 48% for femoropopliteal bypasses and was 58% for femorotibial bypasses. In contrast, the secondary patency rate (patency maintained by thrombectomy, thrombolysis, or revision) at 36 months was 89% and 80% for femoropopliteal and femorotibial bypasses, respectively. The improved secondary patency was due to postoperative surveillance of graft hemodynamics and the success of graft revision. Problems unique to the in situ technique (incomplete valve incision, residual arteriovenous fistula, graft torsion and entrapment) accounted for 58% of early (less than 30 days) graft revisions and 52% of late revisions. The use of Doppler spectral analysis at operation and duplex scanning after operation can locate unsuspected technical errors and identify grafts with low flow at increased risk for failure. The primary patency of the in situ bypass mandates objective assessment of valve incision sites at operation and a protocol of postoperative surveillance to identify grafts that require revision. Early surgical intervention of hemodynamically abnormal but patent in situ bypasses is rewarded by excellent secondary patency.

Bacterial adherence to vascular prostheses: A determinant of graft infectivity

An in vitro model was developed to quantitatively measure bacterial adherence to the surface of prosthetic vascular graft material. Four strains of bacteria (Staphylococcus aureus, nonmucin-producing S. epidermidis [SP-2], mucin-producing S. epidermidis [RP-12], and Escherichia coli) were used to inoculate expanded polytetrafluoroethylene (ePTFE), woven Dacron, and velour knitted Dacron graft material. After graft specimens were incubated in a 10(7) suspension of bacteria, they were washed to remove nonadherent organisms and ultrasonically oscillated to dislodge adherent organisms. Quantitative culture of the sonication effluent was used to calculate bacterial adherence, expressed as the number of colony-forming units found in each square centimeter of graft material per 10(7) inoculum. All bacterial strains had a greater affinity to velour knitted Dacron graft than to ePTFE (p less than 0.025). E. coli and S. aureus adhered to velour knitted Dacron in greater numbers than to woven Dacron (p less than 0.04). The production of extracellular polysaccharide (mucin) by the RP-12 strain significantly increased adherence to both EPTFE and Dacron grafts compared with the other three bacterial strains tested (p less than 0.04). Although E. coli was less adherent to ePTFE than nonmucin-producing staphylococcal strains (S. aureus and SP-2), no difference in adherence to knitted or woven Dacron graft material was demonstrated. The differential adherence of bacteria to prosthetic vascular grafts pays an important role in the pathogenesis of graft sepsis and determines relative graft infectivity. The in vitro model developed is well suited for further study of the mechanisms by which bacteria adhere to and colonize vascular grafts.

In situ replacement of vascular prostheses infected by bacterial biofilms

Late prosthetic graft infections are commonly the result of coagulase-negative staphylococci that survive within a biofilm on prosthetic surfaces and provoke perigraft inflammation. The indolent nature and microbiologic characteristics of bacterial biofilm infections coupled with the morbidity of graft excision and extraanatomic bypass grafting prompted us to use in situ graft replacement in 15 patients admitted to the hospital with 17 infected graft segments at a mean (+/- SEM) time interval of 70 +/- 16 months after graft implantation (n = 6) or revision (n = 9). Since 1986, 17 grafts (14 aortofemoral, 2 axillofemoral, and 1 femoropopliteal) infected by bacterial biofilms have been treated. Signs on admission included femoral pseudoaneurysm (n = 7), perigraft abscess (n = 6), or graft-cutaneous sinus tract (n = 4). No patient exhibited septicemia. At operation graft incorporation was absent and Grams stain of perigraft exudate showed polymorphonuclear leukocytes but no bacteria. Culture of explanted graft material isolated coagulase-negative staphylococci (n = 12), Staphylococcus aureus (n = 1), and no growth (n = 2). All patients were successfully treated by a regimen that included parenteral antibiotics, removal of involved graft material, excision of inflamed perigraft tissue, and in situ replacement with an expanded polytetrafluoroethylene prosthesis. No deaths, graft thromboses, or deep wound infections occurred after operation. Recurrent graft infection did not develop during a follow-up interval that ranged from 5 to 50 months (mean, 21 months). Diagnosis of vascular prosthesis infection caused by bacterial biofilms can be based on signs at admission and operative findings. Complications of this perigraft infection can be eradicated by antibiotic administration, local debridement, and in situ graft replacement.

Durability of vein graft revision: The outcome of secondary procedures

Occlusive lesions that reduced graft blood flow and ankle systolic pressure were identified in 83 femorodistal saphenous vein bypasses by use of duplex scanning or arteriography. Sites of stenosis included vein conduit (n = 41), anastomoses (n = 20), outflow arteries (n = 15), or inflow (n = 9) arteries. One hundred three secondary procedures consisting of vein-patch angioplasty (n = 31), sequential (n = 21) or interposition (n = 17) graft placement, percutaneous transluminal balloon angioplasty (n = 17), or excision of the lesion and primary anastomosis (n = 16) were performed to correct primary (n = 85) or recurrent (n = 18) graft stenoses. Cumulative graft patency after reintervention was 96% at 1 year, and 85% at 5 years. Stenosis or occlusion of revision sites was less after excision (0 of 16) or replacement (1 of 17) of abnormal segments compared to vein-patch angioplasty (8 of 31) or balloon angioplasty (9 of 18). Sequential or jump grafts constructed to improve graft outflow impaired by either myointimal or atherosclerotic occlusive lesions were the least durable secondary procedures. Five of eight graft failures in this series resulted from sequential/jump graft occlusion. All categories of secondary procedures normalized graft and limb hemodynamics, although only one third of patients reported symptoms of limb ischemia before revision. Surveillance of infrainguinal vein bypasses for occlusive lesions is a valid concept to salvage patent but hemodynamically-failing grafts. Secondary procedures that excised the lesion, used autologous tissue reconstruction, and normalized hemodynamics at the revision site and in the vein bypass were associated with a low incidence of restenosis and prolonged graft patency.

An outcome analysis of carotid endarterectomy: The incidence and natural history of recurrent stenosis ☆ ☆☆ ★ ★★

PURPOSE This report identifies the incidence of recurrent carotid stenosis after carotid endarterectomy (CEA) and records the natural history of the disease process to gain further insight into its proper management. METHODS A prospective surveillance protocol with duplex imaging and velocity spectral analysis was used to detect recurrent stenosis ( > 50% diameter reduction) and to document the clinical outcomes of patients who underwent CEA. Between 1984 and 1993, 619 consecutive CEAs were performed in 587 patients. RESULTS Recurrent carotid stenosis developed in 48 CEA sites (7.8%) during a mean follow-up interval of 34 months (range, 2 to 118 months). Normal results on intraoperative assessment correlated with a 5.6% incidence of recurrent stenosis, compared with a 19% incidence when a residual hemodynamic abnormality was present (p < 0.0003). In the first year after surgery, there were no transient ischemic attacks, strokes, or carotid occlusions from recurrent stenosis, compared with a 27% morbidity rate in later follow-up (p < 0.01). Three patients with recurrent stenosis subsequently had occlusion at the CEA site, two of whom had severe ipsilateral strokes. CONCLUSIONS The incidence of recurrent carotid stenosis is low. Patients are at significant risk for neurologic morbidity when a recurrent stenosis occludes. With a 0.3% incidence of late stroke resulting from carotid bifurcation disease, these data confirm that CEA does provide long-term protection from stroke.