Use of intravascular ultrasound as a "Quality Control" technique during carotid stent-angioplasty: are there risks to its use?

Intravascular ultrasound (IVUS) provides high-resolution vessel imaging and has been shown to improve clinical outcomes when used to assess the technical result of peripheral angioplasty procedures. Our vascular group compared anatomic and clinical outcomes of carotid artery stent-angioplasty (CAS) performed with angiogram monitoring alone, or in combination with IVUS imaging to select stent/balloon diameter and interrogate stent deployment region for residual stenosis. A retrospective review of our carotid stent registry (N=306) identified 220 CAS procedures performed with either a digital C-arm fluoroscopy alone (N=110) or in conjunction with IVUS (N=110) with at least 6-month of clinical follow-up. Outcome measures of procedure time, angioplasty balloon diameter, contrast dye volume, Duplex surveillance testing for recurrent stenosis, and procedure event (death, cardiac, neurologic) rates were compared to assess the risks and benefits of IVUS. All procedures utilized a cerebral protection device deployed prior to IVUS imaging. Procedure times were similar, but IVUS usage resulted in lower (P<0.05) contrast agent volumes due to fewer angiogram runs for stent sizing and verification of adequate stent deployment. IVUS imaging resulted in the use of larger diameter balloons (typically 6 mm) for final stent angioplasty based on distal internal carotid artery (ICA) dia measurements, and identified (P<0.01) more residual stent abnormalities (N=12, 11%) versus CAS with angiogram assessment alone (N=2, 1.8%). No procedural or 30-day cardiac events or deaths occurred. The overall stroke rate was 0.9%; two events (stroke-1; reperfusion injury-1) in the angio+IVUS group (1.8%) and none in the angio alone group. Duplex ultrasound surveillance following CAS demonstrated a higher (P<0.01) incidence of >50% diameter-reducing in-stent stenosis in the angio alone group (11% vs 7% at 1 month ; 24% vs 6% at last surveillance; mean 36 moontha; range: 6-66 months). The quality control of the CAS procedure was enhanced by IVUS imaging which directed stent /balloon sizing and was more accurate than angiography in confirming adequate stent expansion. No IVUS related adverse events occurred. Based on the anatomic information provided by IVUS, larger diameter angioplasty balloons were used which correlated with less residual stenosis after CAS based on duplex ultrasound testing.

Safe intraluminal shunting during carotid endarterectomy.

The major complications associated with shunting include embolization at the time of insertion and shunt thrombosis. Increased technical difficulty of performing the endarterectomy with an inlying shunt hs also contributed to lack of surgeon acceptance. These problems can be minimized by using a short, flexible shunt with a sidearm attachment. The shortness enables the shunt to lie within the vessel, while the flexibility enables manipulation of the shunt to optimize exposure of all segments of the vessel. The sidearm allows flushing of both limbs and helps prevent embolization while providing a means for rapid assessment of shunt patency. The technique provides a safe and simple method of shunting during carotid endarterectomy.

Monocular ischemia--the influence of carotid atherosclerosis versus primary ocular disease on prognosis.

The etiology of monocular ischemia influences the clinical manifestation and long-term neurologic and visual prognosis. During a 10-year period, 140 patients with monocular visual symptoms were evaluated and assigned to a carotid bifurcation occlusive disease group (group I) or a primary ocular disease group (group II) on the basis of angiographic findings and ophthalmologic evaluation. Patients with symptoms secondary to emboli from the carotid bifurcation tended to have a shorter duration of blindness and a lower incidence of permanent blindness initially and during follow-up. The presence of Hollenhorst plaques or retinal artery occlusion did not have any discriminatory diagnostic value since the incidence was similar in both patient groups. Since both primary eye disease and carotid bifurcation occlusive disease can be initially seen as monocular ischemia, carotid angiography and ophthalmologic consultation are necessary to select those patients who will benefit from carotid endarterectomy.

A low flow velocity predicts failure of femoropopliteal and femorotibial bypass grafts.

The prognostic value of Doppler-derived blood flow velocity measurements for predicting the patency of femoropopliteal and femorotibial bypass grafts was analyzed. Peak systolic and end-diastolic blood flow velocities were measured in 42 femorotibial, 24 femoropopliteal, and three femoropopliteal (isolated segment) in situ saphenous vein bypasses at operation and serially in the postoperative period. At operation peak systolic flow velocity was greater (p less than 0.01) in femoropopliteal grafts (90 +/- 22 cm/sec) compared with femorotibial grafts (68 +/- 19 cm/sec) and isolated segment femoropopliteal (58 +/- 16 cm/sec) grafts. Diastolic forward flow, indicative of low outflow resistance, was present in all successful grafts at operation and in the immediate postoperative period, but decreased thereafter. Early graft occlusion was associated with a low peak systolic flow velocity (less than 40 cm/sec) and absent diastolic forward flow. Postoperative decrease in peak systolic velocity to less than 45 cm/sec identified grafts with impending failure due to intrinsic graft lesions or progression of atherosclerosis. A low blood flow velocity threatens graft patency and should prompt an angiographic evaluation to identify correctable graft lesions or an outflow tract suitable for sequential grafting for the purpose of augmenting flow velocity.

The microbiology of explanted vascular prostheses.

The incidence of bacterial colonization and the microflora of prosthetic vascular graft material explanted from 44 patients undergoing graft revision was determined. Graft material for culture was obtained from aortofemoral or femoropopliteal vascular prostheses without signs of infection but requiring revision for femoral anastomotic aneurysm (n = 21) or thrombosis (n = 26). Explanted graft material was placed in tryptic soy broth and ultrasonically oscillated to disrupt the adherent graft surface biofilm, which is a technique that increases the recovery of microorganisms compared with standard microbiologic culture methods. Microorganisms were isolated from 90% (19/21) of grafts associated with anastomotic aneurysms and 69% (18/26) of thrombosed grafts. Staphylococcus epidermidis was the prevalent organism recovered and accounted for 69% of the isolates. Slime production, a growth characteristic of S. epidermidis associated with prosthetic device infection in humans, was demonstrated by 87% (13/15) of strains isolated from grafts with pseudoaneurysms compared with 33% (4/12) of strains isolated from occluded grafts (p less than 0.01). Despite the high incidence (79%) of colonization of vascular prostheses, no patient developed wound or graft infection after graft replacement and perioperative antibiotic administration. Low-virulent microorganisms, such as S. epidermidis, can colonize vascular prostheses and not provoke signs of graft infection. The high recovery rate of slime-producing S. epidermidis strains from grafts with anastomotic aneurysms and the adherence-mediated growth of these bacteria on biomaterials suggest this late graft complication is the sequelae of a bacteria-laden biofilm infection.

Use of the internal jugular vein for carotid patch angioplasty.

The internal jugular vein is an excellent source of autogenous tissue for carotid artery reconstruction because of its availability in the operative incision, adequate size, and ability to be harvested without morbidity. For 153 of 453 consecutive carotid reconstructions, the durability of the internal jugular vein (n = 76) and the greater saphenous vein (n = 77) as a patch angioplasty was compared. Mean postoperative follow-up was 17 months (1 to 52 months). The vein-patched carotid-bifurcation was studied by means of duplex ultrasonography to assess patency, detect restenosis, and measure cross-sectional diameter during systole. No carotid bifurcation occluded after operation. No ruptures or aneurysmal dilatations of the vein patches were observed. The maximum diameter (mean +/- SD) of the carotid patch angioplasties constructed with internal jugular vein (9.4 +/- 1.9 mm) was similar to patches made with greater saphenous vein (9.6 +/- 1.7 mm). In 95 patients serial duplex examinations demonstrated maximum diameter changes of the vein-patched internal carotid artery ranging from an increase of 3.5 mm to a decrease of 3.0 mm. Asymptomatic restenosis (greater than 50% diameter reduction) was detected in 2/95 (2.1%) patients. Because of the premium placed on the saphenous vein for peripheral arterial reconstruction and coronary artery bypass grafting, the ipsilateral internal jugular vein should be used more frequently for carotid patch angioplasty.

Symptomatic recurrent carotid stenosis and aneurysmal degeneration after endarterectomy.

BACKGROUND: Aneurysmal degeneration of a carotid reconstruction was not recognized until the patient, who was known to have recurrent carotid artery stenosis, had a thromboembolic stroke. This sequelae of carotid endarterectomy is a serious complication, associated with a high morbidity and mortality rate. This review was conducted to establish the risk of transient ischemic attack and stroke for patients found to have recurrent carotid stenosis associated with aneurysmal degeneration of the carotid artery after endarterectomy. METHODS: A case is reported, and 100 literature references of aneurysmal degeneration of the carotid artery after endarterectomy were reviewed. RESULTS: False aneurysm from anastomotic disruption was the most common presentation identified in the cases reviewed. Nineteen of the patients had a significant neurologic event; however, three (50%) of six patients with aneurysm and recurrent carotid artery stenosis had a transient ischemic attack or stroke. CONCLUSIONS: The incidence of neurologic symptoms is markedly increased when recurrent carotid artery stenosis is associated with carotid aneurysm. During postoperative surveillance after endarterectomy, the identification of recurrent carotid artery stenosis requires evaluation for aneurysmal degeneration of the carotid artery with duplex scanning. These patients are at significant risk for transient ischemic attack and stroke. This rare complication merits operative repair.

Adherence of mucin and non-mucin-producing staphylococci to preclotted and albumin-coated velour knitted vascular grafts.

The mechanisms involved in bacterial adherence to vascular grafts are important in understanding prosthetic infections. Albumin-coated Dacron (ACD) is a new development in vascular graft fabrication. However, albumin acts as a receptor for certain gram-positive bacterial adhesions. Five pathogenic, coagulase-negative Staphylococcus epidermidis strains were used to measure the differential microbial adherence to ACD versus untreated velour-knitted Dacron (VKD) vascular prostheses. Specimens of VKD, preclotted VKD, and ACD were inoculated with each of the five strains (10(7) colony-forming units/ml) for 2, 4, 8, 12, and 24 hours. After incubation, graft specimens were washed to remove nonadherent organisms and oscillated ultrasonically to remove adherent organisms. The sonication effluent was plated to trypticase soy agar to quantitate the adherent organisms. Adherence was significantly greater (p less than 0.01) to VKD compared with preclotted VKD and ACD at 2, 4, 8, and 24 hours. Four of the five study strains demonstrated significantly greater adherence to VKD than to either ACD or preclotted VKD. Adherence of S. epidermidis increased with exposure time. Albumin bonded to velour-knitted Dacron does not increase coagulase-negative staphylococcal adherence compared with the noncoated vascular prostheses. Binding albumin to vascular prostheses does not increase the risk of staphylococcal colonization.

Comparison of serum and tissue antibiotic levels in diabetes-related foot infections.

Parenteral antibiotics are used as an adjunct to amputation or operative debridement for patients with diabetes who require emergency surgery for a septic foot. In 26 patients with a diabetes-related foot infection, one dose of various intravenous antibiotic regimens (gentamicin and clindamycin, ticarcillin/clavulanate, ampicillin/sulbactam) was administered during the hour before the procedure, and assays were performed to measure the antibiotic serum and tissue levels at the time of surgical debridement. Aerobic and anaerobic cultures were performed on infected tissue. The 172 bacterial isolates, including 95 aerobes and 77 anaerobes, (6.6 isolates per patient) underwent antibiotic susceptibility testing. Antibiotic levels were calculated by biologic assay from serum and tissue biopsies from the viable margins of the surgical site, which subsequently healed primarily or supported a split-thickness skin graft. Sixteen of the patients achieved therapeutic serum levels, and therapeutic tissue levels were reached in six patients at the time of surgery. A significantly lower number of patients had therapeutic tissue levels compared to serum levels (p less than 0.01, chi square). Initial intravenous antibiotic administration provides inadequate tissue concentrations for treating foot infections in patients with diabetes. Adequate serum antibiotic levels do not reflect therapeutic tissue antibiotic levels at the surgical margins in this group of patients.

Diagnosis and treatment of biomaterial-associated vascular infections.

Management of biomaterial-associated vascular infections requires an understanding of pathogenetic mechanisms, risk factors, and microbiologic characteristics. Staphylococci sp., especially slime-producing strains of S. epidermidis are the prevalent pathogens. Experimental and clinical studies have indicated in situ replacement, particularly with an antibiotic-bonded prosthesis, as effective treatment for infections caused by coagulase-negative staphylococci. When sepsis is a presenting sign, prompt intervention, total excision of the prosthesis, and antibiotic administration are required.

Detection of technical error during arterial surgery by pulsed Doppler spectral analysis.

Pulsed Doppler spectral analysis of midstream flow was compared with arteriography in 90 patients following carotid endarterectomy (N = 60) or lower-extremity bypass grafting (N = 30) for the detection of unsuspected technical error. Spectral changes in the velocity waveform indicating flow disturbance were identified in the endarterectomy or anastomotic sites of 11 patients (12%). All were associated with an anatomic defect apparent on arteriography. The revision of major defects in six patients (7%) corrected the flow disturbance. The absence of flow disturbance in 79 patients (88%) predicted a technically satisfactory arterial reconstruction. Intraoperative assessment by pulsed Doppler spectral analysis is a noninvasive, rapid, and accurate method for detecting technical errors during arterial surgery. The high sensitivity of this method makes it suitable for use as a screening test, resulting in the selective use of operative arteriography.

Upper-extremity emboli secondary to axillofemoral graft thrombosis.

Four episodes of upper-extremity arterial emboli following axillofemoral bypass graft thrombosis are described. The source of the embolus was the blind stump of the proximal portion of the graft limb that remained patent after graft occlusion. With axillofemoral graft thrombosis, management requires treatment of the lower-limb ischemia and an awareness of the embolic potential of the acutely thrombotic graft limb. Patient evaluation and the surgical management of axillofemoral graft thrombosis with and without the complication of upper-extremity ischemia are discussed, as well as the etiology and prevention of this complication.

Classification of carotid bifurcation disease using quantitative Doppler spectrum analysis.

Spectrum analysis of continuous-wave Doppler recordings from the region of the carotid bifurcation was used to classify the degree of stenosis in the internal (ICA) and external (ECA) carotid arteries. Measurements of systolic peak frequency, end-diastolic frequency, and the degree of spectral broadening were used to define five ICA disease categories: 0% to 15% diameter reduction (DR), 16% to 49% DR, 50% to 80% DR, greater than 80% DR, and occlusion. The results were compared to contrast arteriography in 122 patients (243 arteries). The agreement with angiography in classifying ICA stenosis was 82%. Doppler spectrum analysis identified 96% of hemodynamically significant disease (greater than 50% DR) in the ICA and ECA and 97% of ICA occlusions. Attention to the common carotid artery waveform and the ICA diastolic frequency improved the accuracy of predicting greater than 80% DR and occlusion of the ICA. Noninvasive classification of carotid bifurcation disease is useful in clinical decision making to select the angiographic technique most likely to accurately define disease morphology and to follow up patients for disease progression.

Intraoperative assessment of in situ saphenous vein arterial grafts using pulsed Doppler spectral analysis.

Errors in anastomotic construction, retained competent valves, and arteriovenous fistulas can cause both early and delayed failure of in situ saphenous vein arterial grafts. Pulsed Doppler spectral analysis of midstream flow was compared with arteriography in 50 consecutive in situ saphenous vein bypasses for the detection of unsuspected technical error. Based on spectral changes in the velocity waveform indicating flow disturbance, intact valve cusps could be distinguished from arteriovenous fistulas, and technically unsatisfactory anastomoses were identified. Competent valve cusps were identified in nine (5%) of 180 valve-incision sites, and six anastomoses (6%) were judged unsatisfactory. The presence of severe flow disturbance was always associated with an anatomic defect on arteriography. Incision of missed valve cusps and anastomotic revisions corrected associated flow disturbances. Doppler flow analysis readily located high-flow arteriovenous fistulas, thereby reducing operative time and the need for multiple arteriograms. The high sensitivity of this method (no false-negative assessments) makes it an ideal screening test, resulting in the selective use of operative arteriography.

Influence of vein-patch angioplasty on carotid endarterectomy healing.

We studied the influence of venous patching on the patency, endothelial regeneration, and wall healing of endarterectomized carotid arteries in a canine model. Thirteen dogs underwent bilateral common carotid endarterectomies (intimectomy and partial media excision). In each dog, one artery was closed by continuous suture and the contralateral artery was closed by external jugular vein-patch angioplasty; arteries were excised at two postoperative intervals (two to three and four to five weeks) for light, scanning, and transmission electron microscopy. The patency of arteries closed primarily (9/13 [69%]) was not significantly different compared with arteries closed with venous patches (12/13 [92%]). By scanning electron microscopy, regeneration of the endothelial monolayer occurred by migration from the endarterectomy end points and suture lines. Despite survival of the vein-patch endothelium, the rate and pattern of reendothelialization was not altered by venous patching. In both patched and unpatched vessels, endothelial regeneration was incomplete at two to three weeks and completed by four to five weeks. The histologic characteristics of the endarterectomized arterial wall after operation were also not influenced by the closure technique. In contrast with the healing artery wall, vein-patch walls did not develop a thickened intima. Although venous patching does not influence early patency, endothelial regeneration, or wall healing after endarterectomy, vein-patch angioplasty does increase vessel diameter and prevents the development of circumferential intimal thickening, attributes that are beneficial in minimizing restenosis.

Hemodynamics of in situ saphenous vein arterial bypass.

Doppler-derived blood flow velocity and limb blood pressure measurements were used to characterize the hemodynamics of 128 in situ saphenous vein arterial bypasses. The magnitude and configuration of the graft velocity waveform was the best predictor of clinical outcome. Successful bypasses had antegrade flow throughout the pulse cycle and a blood flow velocity above 40 cm/s. A low graft blood flow velocity (less than 40 cm/s) was associated with technical error or early graft failure due to poor runoff. The return of normal limb blood pressure correlated with a technically satisfactory bypass but was measured in only 50% of limbs on the first day after surgery. In 28 bypasses with high blood flow velocity (mean +/- SD) in systole (102 +/- 20 cm/s) and diastole (35 +/- 11 cm/s), postoperative limb blood pressure was initially low (mean ankle-brachial pressure index = 0.68) due to restriction of blood flow through small-diameter (less than 4-mm) venous conduits. As revascularization hyperemia abated, diastolic blood flow velocity decreased and limb blood pressure normalized. Despite the high blood flow velocity and pressure gradient associated with flow-restrictive venous conduits, limb ischemic symptoms resolved, and graft patency was not decreased. An understanding of graft and limb hemodynamics after in situ bypass grafting is critical when noninvasive diagnostic techniques are used to document technical adequacy and for postoperative surveillance.

Surface biofilm disruption. Enhanced recovery of microorganisms from vascular prostheses.

Ultrasonic oscillation (sonication) of explanted vascular prosthetic graft material can disrupt surface biofilms and increase the recovery of adherent microorganisms. Recovery of microorganisms from vascular grafts was studied in a canine model of Staphylococcus epidermidis graft contamination (N = 26) and on graft material excised from patients undergoing femoral anastomotic pseudoaneurysm repair (N = 7). Surface biofilm disruption by sonication significantly increased the incidence of positive cultures of excised graft material compared with broth (P less than .010) and blood agar plate (P less than .005) culture techniques. The S epidermidis was recovered from 31% of the canine vascular grafts and 100% of the clinical specimens. The in vitro production of a glycocalyx "slime" was demonstrated in 73% of the recovered staphylococcal strains. The formation of an adherent bacteria biofilm on implanted vascular prostheses is not an uncommon occurrence and is an important factor in the pathogenesis of anastomotic pseudoaneurysm formation and late graft infection.

Protein C deficiency. A cause of unusual or unexplained thrombosis.

Familial hypercoagulable states are a collection of syndromes characterized by an inherited deficiency of various proteins involved in the control of coagulation and include antithrombin III, plasminogen, protein C, and protein S. Affected patients usually develop venous thrombosis as adults. During a 15-month interval, we identified five patients with venous thrombosis accompanied by protein C deficiency. Four patients presented with deep venous thrombosis, which was recurrent in two, and one patient developed mesenteric venous thrombosis. The kindred of this last patient suggested an autosomal dominant genetic transmission of protein C deficiency. Patients' ages at the time of diagnosis of disease ranged from 28 to 41 years. All patients had low levels of protein C (range, 34 to 67 U/dL; normal, 70 to 130 U/dL). All patients were treated with heparin sodium immediately and then given long-term oral anticoagulation therapy with warfarin sodium. Protein C deficiency is a predisposing factor to the development of venous thrombosis that has only recently been recognized. Treatment of symptomatic protein C deficiency requires short-term heparin therapy followed by long-term oral anticoagulation therapy with warfarin. Oral anticoagulation treatment must be initiated slowly with no loading dose to avoid warfarin-associated skin necrosis. Patients with unexplained or unusual thrombosis, especially if it occurs at an early age, and patients with recurrent episodes of lower limb venous thrombosis should have their protein C levels measured. If a deficiency is documented, long-term warfarin anticoagulation therapy is recommended.

Aortofemoral graft infection due to Staphylococcus epidermidis.

A ten-year review of aortofemoral graft infection documented Staphylococcus epidermidis as the infecting organism in 18 (60%) of 30 cases. Diagnosis of such infection required a high index of suspicion because of its late postoperative appearance (mean interval of 41 months) and the inability to identify a microorganism at operation by routine wound culture or Gram's stain. Clinical findings suggesting graft infection included multiple anastomotic aneurysms (18 patients), perigraft exudate (16 patients), a draining groin mass (five patients), and aortoduodenal fistulas (two patients). Due to the low concentration and virulence of the organism, aerobic culture of the prosthetic fabric in broth media provided the optimum method of confirming the S epidermidis infection. Total graft excision with immediate vascular reconstruction was the preferred treatment method and resulted in a mortality and major amputation rate of 11%.

Carotid artery stenosis following endarterectomy.

Duplex scanning and spectral analysis were used to detect carotid artery stenosis following 89 endarterectomies in 76 patients with a mean postoperative follow-up interval of 16 months. Operative arteriography was used in all cases to verify the technical result. Spectral changes indicating greater than 50%-diameter internal carotid stenosis were observed postoperatively in 32 of the 89 sides. Serial follow-up of 22 stenotic sides showed persistent stenosis in 12, regression of stenosis in nine, and internal carotid occlusion in one. The estimated overall incidence of persistent high-grade stenosis was 19%. Recurrent neurologic symptoms occurred in eight patients. This incidence of postoperative carotid stenosis is higher than estimates based on clinical criteria. The transient nature of some early postoperative stenosis is consistent with proliferation and regression of myointimal lesions in response to arterial injury.