Expected changes in physician outpatient interventional practices as a result of coronavirus disease 2019 and recent changes in Medicare physician fee schedule.

OBJECTIVE: We examined the economic and practice effects of the coronavirus disease 2019 (COVID-19) pandemic and decreased Medicare physician payments on outpatient vascular interventional procedures. METHODS: A 21-point survey was constructed and sent electronically to the physician members of the Outpatient Endovascular and Interventional Society and the American Vein and Lymphatic Society. The survey responses were converted to a Likert scale and statistical analyses performed to examine the associations between the response variables and the characteristics and practice patterns of the physician respondents. RESULTS: A total of 165 physicians responded to the survey, of whom 33% were vascular surgeons, 18% were radiologists, and 15% were general surgeons. For slightly more than one half (55%), their interventional practice was limited to the office setting, with the remainder also performing procedures in an office-based laboratory (OBL), ambulatory surgery center (ASC), or hospital. Almost all respondents had performed superficial venous interventions, with slightly more than one third also performing either deep venous procedures and/or peripheral arterial interventions. The COVID-19 pandemic had affected 98% of the practices, with a staff shortage reported by 63%. The most-established physicians, those with the longest interval since training completion, were the least likely to have experienced staff shortages. Almost all (94%) the respondents expected that the recent Medicare payment changes will have a negative effect on their practice. Physicians with only an office-based practice were less likely to add a physician associate compared with those with an OBL (P = .036). More than one quarter reported that it was likely they would close or sell their interventional practice in the next 2 years and 43% reported they were planning to retire early. The anticipated ameliorative responses to the decreased Medicare physician payments included adding wound care (24%) or other clinical services (36%) to their practices, with the alternatives considered more by younger physicians (P = .002) and nonsurgeons (P = .047). Only 10% expected to convert their practices to an ASC or hybrid ASC/OBL (16%). CONCLUSIONS: The emotional and economic effects of the COVID-19 pandemic and the decreased Medicare physician reimbursement rates for vascular outpatient interventionalists have been significant. Even greater challenges for the financial viability of office practices and OBLs can be expected in the near future if additional further planned cuts are put into effect.

Effectiveness and safety of repeated percutaneous intervention in an office-based endovascular center in maintaining hemodialysis access.

OBJECTIVES: Percutaneous dialysis access interventions are routinely used to maintain the patency of dialysis access despite the lack of data regarding their long-term effectiveness. This retrospective study was undertaken to study the effectiveness and safety of percutaneous dialysis access interventions in arm fistulas and bridge grafts in an office-based endovascular center. METHODS: Patients who had a percutaneous dialysis access intervention in their upper extremity access site, performed at a single office-based endovascular center over a nine-year period (2007-2016) were included in this study. The patients' demographic factors, patency, and complications were analyzed. Patients were entered in the study after first percutaneous dialysis access intervention. RESULTS: A total of 298 limbs in 259 patients had 913 procedures carried out over a nine-year period. There were 190 access arteriovenous fistulas and 108 arteriovenous grafts. The two most common arteriovenous fistulas were the brachiocephalic fistula (n = 74, 39%) and radio cephalic fistula (n = 69, 36%). Arteriovenous grafts were most commonly placed in the upper arm (n = 66, 61%) followed by the forearm (n = 42, 39%). The mean overall patency for all limbs was 50.86 months. Arteriovenous fistulas had a significantly longer patency than arteriovenous grafts (51.65 vs. 42.09 months; P = 0.01). In addition, patients with two or more percutaneous dialysis access intervention in their arteriovenous fistula had significantly greater patency than those with only one percutaneous dialysis access intervention (58.5 vs. 7.6 months; hazard ratio 0.41; P = 0.0008). This was not true for the arteriovenous graft group. Women represented 49% of the patient group. Their accesses had shorter patency than men (39.8 vs. 60 months; P = 0.0007). CONCLUSIONS: This data support the use of repeated percutaneous dialysis access intervention to maintain long-term patency of dialysis access sites in an office-based endovascular center. Overall, fistulas have longer patency than grafts and women have poorer outcomes as compared to men.

Safety and efficacy of transcarotid artery revascularization in a community hospital.

OBJECTIVE: We evaluated the outcomes and complications of transcarotid artery revascularization (TCAR) outside of academic vascular surgery programs. METHODS: An institutional review board-approved retrospective study was performed. Data from all cases of TCAR performed at a community hospital from May 2017 to February 2020 were collected and analyzed. Seven vascular surgeons performed the procedures after receiving appropriate training. The primary outcomes included technical success, the need for further revascularization, and major adverse events (death, cerebrovascular accident [CVA], myocardial infarction). The secondary outcomes included other adverse events and complications. The outcomes were assessed in the perioperative and 30-day follow-up periods. RESULTS: During a 33-month period, TCAR was completed in 147 of 149 attempted cases (98.7%). No patients required further revascularization. The perioperative and 30-day major adverse event rates were 0.7% (n = 1) and 3.4% (n = 5), respectively. One case of a minor perioperative CVA occurred. At 30 days, one patient had died. The 30-day complications included CVA (n = 1) and myocardial infarction (n = 3). The combined perioperative and 30-day minor complication rates were 2.7% and 1.4%, respectively. CONCLUSIONS: TCAR is a safe and effective method of carotid artery revascularization in a community hospital setting. This technology might help improve revascularization in patients without access to larger academic centers.

Improving Inferior Vena Cava Filter Retrieval and Success Rates Using an Office Endovascular Center.

BACKGROUND: The Food and Drug Administration recommends that retrievable inferior vena cava filters (IVCFs) be removed 29-54 days postinsertion. Nationally, the retrieval rate is around 23-25%. The objectives of this study are to assess the effect of a plan for IVCF retrieval and access to an office endovascular center (OEC) on filter removal rates and to assess the safety of the procedure in an OEC. METHODS: In this institutional review board-exempt retrospective study, the medical records of all patients who had an IVCF placed or removed in the hospital and OEC setting by one group of vascular surgeons between January 2011 and February 2017 were analyzed. Informed consent was not required for this retrospective chart review. The following data were abstracted: filter model, procedure site, retrieval plan, number of removal attempts, complications attributed to removal, success of removal, and the duration that the filter was in place. Anticoagulation was not discontinued before filter retrieval. Filters were removed under local anesthesia with or without mild conscious sedation. RESULTS: IVCF removal was attempted in all eligible patients, 120 of 191 with IVCFs, whereas 71 patients were lost to follow-up (46), died (19), or the indication changed (6). Of the patients who had filters placed in the hospital (n = 161), 62% were removed (n = 101), of which 86% had a removal attempt in the OEC, whereas 14% had the filter removed in the hospital. Sixty-three percent of patients who had filters placed in the OEC (n = 30) had the filter removed in the OEC (n = 19). All patients with a newly placed filter were given an office appointment with a vascular surgeon for evaluation and removal planning. Of patients who had their filter removed at the OEC, all were removed via the jugular approach, resulting in 103 of 106 (97%) successful removals in the OEC. Visipaque (GE Healthcare, Chicago, IL) contrast was used during filter removal. Intravascular ultrasound was not used because the study predates the insurance coverage of this technology in the office laboratory. There was no mortality related to filter removal. In addition, there were no bleeding complications, despite patients remaining on anticoagulant therapy during the removal. In 4% of patients, the filter was removed in less than 3 weeks, 30% of patients between 3 and 6 weeks, 26% of patients between 6 weeks and 3 months, and 40% of patients after 3 months. CONCLUSIONS: Having access to both an OEC and a documented retrieval plan increases the frequency of IVCF removal in a community compared with national rates. Retrievable filters can be safely removed in an OEC with extremely high success and safety. Anticoagulation therapy can be continued during retrieval attempt without increased risk of bleeding.

Outcomes of atherectomy for lower extremity ischemia in an office endovascular center.

OBJECTIVE: To evaluate the safety and effectiveness of infrainguinal artery revascularization via atherectomy supplemented with other endovascular techniques in an office endovascular center (OEC) setting. METHODS: A retrospective study was conducted examining 352 lower extremity atherectomy revascularization procedures between 2011 and 2016 at an OEC by five board-certified vascular surgeons. Patients received laser atherectomy or orbital atherectomy followed by angioplasty or angioplasty and stent placement as needed. Reintervention was indicated based on evidence of clinical symptoms and imaging studies. Demographics, vessel-specific data, treatment information, and outcome of procedures were recorded. Data analysis was carried out using Kaplan-Meier survival curves. RESULTS: Lower extremity atherectomy was carried out in 282 patients in 352 limbs with average age of 69 ± 11 years. Technical success of <30% residual stenosis by angiogram was achieved in 571/594 vessels treated. Within 30 days of procedure, 23/352 limbs required major amputation resulting from pre-existing disease, ranging from 3 Rutherford class 4, 17 Rutherford class 5, to 3 Rutherford class 6 limbs. No 30-day mortality was noted. The primary patency of the 571 treated vessels at 12 months was 90%, and 84% at 29 months. The patency of treated vessels that reached >50% stenosis on follow-up and required reintervention (51/571 vessels) or did not require reintervention (79/571) was 72% and 87% at 23 months' follow-up, respectively, with no difference in risk of occlusion identified (P = .181). There was a significantly increased risk of occlusion for vessels treated with laser atherectomy as compared with orbital atherectomy (odds ratio, 2.552; 95% confidence interval, 1.375-4.735; P = .003). No significant difference in risk of occlusion was found between treatment with atherectomy and angioplasty (466/571 vessels) compared with atherectomy, angioplasty, and stenting (102/571) with secondary patency of 90% and 85% at 6 months' follow-up, respectively. There was no difference in patency between claudicants and patients with critical limb ischemia. CONCLUSIONS: Atherectomy in conjunction with angioplasty and/or stenting has satisfactory patency with minimal complications when the procedure is carried out in an OEC. Asymptomatic >50% restenosis of treated vessels does not warrant reintervention unless the patient presents with clinical symptoms. Various atherectomy devices may result in different outcomes.

Analysis of the retrograde tibial artery approach in lower extremity revascularization in an office endovascular center.

OBJECTIVE: The objective of this study was to evaluate the safety and efficacy of a retrograde tibial approach in revascularization of lower extremities for treatment of ischemia in anatomically challenging patients. METHODS: This is a retrospective study of 57 procedures performed between 2012 and 2016 using the retrograde approach to treat patients with flush occlusion, inability to cross the lesion, failed bypass, or hostile groin. Demographic data, Rutherford classes, vessels treated, and approach were noted. Type of procedure, complications, amputations, deaths, and patency of access tibial vessels and treated vessels were recorded. Ultrasound-guided tibial access was achieved through the anterior tibial artery, posterior tibial artery, or peroneal artery. Technical success was defined as residual stenosis of <30%. Restenosis was defined as two times increase in velocity at the site of treatment. In follow-up, access vessel patency and treated vessel patency were evaluated by physical examination and ultrasound. Kaplan-Meier survival curves were used to assess proportional hazards before using the marginal Cox model to determine statistical significance in risk of postintervention occlusion. RESULTS: In 53 patients (32 men) with an average age of 67 ± 10.6 years, Rutherford categories were as follows: class 2, n = 1; class 3, n = 37; class 4, n = 5; class 5, n = 12; and class 6, n = 2. Tibial arteries were successfully accessed in all limbs. Lesions were crossed in 56 of 57 limbs. One procedure was terminated because of local arterial dissection. Revascularization was achieved in 55 of 57 limbs. Within 30 days of the procedure, 2 of 2 Rutherford class 6 patients and 1 of 12 class 5 patients needed major amputation because of pre-existing disease. There was no 30-day mortality. Of 103 vessels treated, technical success was achieved in 97 (94%). Secondary patency for 103 vessels was 79% with mean follow-up of 6.66 ± 5.4 months. The primary patency was 90% compared with a primary assisted patency of 51%. There was no statistically significant difference in access vessel primary patency in follow-up: 86% (30/35) for anterior tibial artery, 80% (16/20) for posterior tibial artery, and 100% (2/2) for peroneal artery. In addition, in follow-up, there was no significant difference in incidence of occlusion of target vessels based on choice of access vessel used (P = .109). CONCLUSIONS: In this group of anatomically challenging patients, a retrograde tibial approach was safely used. Accessing the tibial artery does not usually cause access vessel occlusion and resulted in no adverse outcomes. The majority of access vessels remained patent for future bypass if necessary.

Guidelines for hospital privileges in vascular surgery and endovascular interventions: Recommendations of the Society for Vascular Surgery.

The Hospital Privileges Practice Guideline Writing Group of the Society for Vascular Surgery is making the following five recommendations concerning guidelines for hospital privileges for vascular surgery and endovascular therapy. Advanced endovascular procedures are currently entrenched in the everyday practice of specialized vascular interventionalists, including vascular surgeons, but open vascular surgery remains uniquely essential to the specialty. First, we endorse the Residency Review Committee for Surgery recommendations regarding open and endovascular cases during vascular residency and fellowship training. Second, applicants for new hospital privileges wishing to perform vascular surgery should have completed an Accreditation Council for Graduate Medical Education-accredited vascular surgery residency or fellowship or American Osteopathic Association-accredited training program before 2020 and should obtain American Board of Surgery certification in vascular surgery or American Osteopathic Association certification within 7 years of completion of their training. Third, we recommend that applicants for renewal of hospital privileges in vascular surgery include physicians who are board certified in vascular surgery, general surgery, or cardiothoracic surgery. These physicians with an established practice in vascular surgery should participate in Maintenance of Certification programs as established by the American Board of Surgery and maintain their respective board certification. Fourth, we provide recommendations concerning guidelines for endovascular procedures for vascular surgeons and other vascular interventionalists who are applying for new or renewed hospital privileges. All physicians performing open or endovascular procedures should track outcomes using nationally validated registries, ideally by the Vascular Quality Initiative. Fifth, we endorse the Intersocietal Accreditation Commission recommendations for noninvasive vascular laboratory interpretations and examinations to become a Registered Physician in Vascular Interpretation, which is included in the requirements for board eligibility in vascular surgery, but recommend that only physicians with demonstrated clinical experience in the diagnosis and management of vascular disease be allowed to interpret these studies.

The Clinical Impact of Cardiology Consultation Prior to Major Vascular Surgery.

OBJECTIVE: To understand statewide variation in preoperative cardiology consultation prior to major vascular surgery and to determine whether consultation was associated with differences in perioperative myocardial infarction (poMI). SUMMARY BACKGROUND DATA: Medical consultation prior to major vascular surgery is obtained to reduce perioperative risk. Despite perceived benefit of preoperative consultation, evidence is lacking specifically for major vascular surgery on the effect of preoperative cardiac consultation. METHODS: Patient and clinical data were obtained from a statewide vascular surgery registry between January 2012 and December 2014. Patients were risk stratified by revised cardiac risk index category and compared poMI between patients who did or did not receive a preoperative cardiology consultation. We then used logistic regression analysis to compare the rate of poMI across hospitals grouped into quartiles by rate of preoperative cardiology consultation. RESULTS: Our study population comprised 5191 patients undergoing open peripheral arterial bypass (n = 3037), open abdominal aortic aneurysm repair (n = 332), or endovascular aneurysm repair (n = 1822) at 29 hospitals. At the patient level, after risk-stratification by revised cardiac risk index category, there was no association between cardiac consultation and poMI. At the hospital level, preoperative cardiac consultation varied substantially between hospitals (6.9%-87.5%, P <0.001). High preoperative consulting hospitals (rate >66%) had a reduction in poMI (OR, 0.52; confidence interval: 0.28-0.98; P <0.05) compared with all other hospitals. These hospitals also had a statistically greater consultation rate with a variety of medical specialties. CONCLUSIONS: Preoperative cardiology consultation for vascular surgery varies greatly between institutions, and does not appear to impact poMI at the patient level. However, reduction of poMI was noted at the hospitals with the highest rate of preoperative cardiology consultation as well as a variety of medical services, suggesting that other hospital culture effects play a role.

Predictors of surgical site infection after open lower extremity revascularization.

OBJECTIVE: Surgical site infection (SSI) after open lower extremity bypass (LEB) is a serious complication leading to an increased rate of graft failure, hospital readmission, and health care costs. This study sought to identify predictors of SSI after LEB for arterial occlusive disease and also potential modifiable factors to improve outcomes. METHODS: Data from a statewide cardiovascular consortium of 35 hospitals were used to obtain demographic, procedural, and hospital risk factors for patients undergoing elective or urgent open LEB between January 2012 and June 2015. Bivariate comparisons and targeted maximum likelihood estimation were used to identify independent risk factors of SSI. Adjusted odds ratios (ORs) were calculated for patient demographics, comorbidities, operative details, and hospital-level factors. RESULTS: Our study population included 3033 patients who underwent 703 femoral-femoral bypasses, 1431 femoral-popliteal bypasses, and 899 femoral-distal vessel bypasses. An SSI was diagnosed in 320 patients (10.6%) ≤30 days after the index operation. Adjusted patient and procedural predictors of SSI included renal failure currently requiring dialysis (OR, 4.35; 95% confidence interval [CI], 3.45-5.47; P < .001), hypertension (OR, 4.29; 95% CI, 2.74-6.72; P < .001), body mass index ≥25 kg/m2 (OR, 1.78; 95% CI, 1.23-2.57; P = .002), procedural time >240 minutes (OR, 2.95; 95% CI, 1.89-4.62; P < .001), and iodine-only skin preparation (OR, 1.73; 95% CI, 1.02-2.91; P = .04). Hospital factors associated with increased SSI included hospital size <500 beds (OR, 2.22; 95% CI, 1.09-4.55; P = .028) and major teaching hospital (OR, 1.66; 95% CI, 1.07-2.58; P = .024). SSI resulted in increased risk of major amputation and surgical reoperation (P < .01), but did not affect 30-day mortality. CONCLUSIONS: SSI after LEB is associated with an increase in rate of amputation and reoperation. Several patient, operative, and hospital-related risk factors that predict postoperative SSI were identified, suggesting that targeted improvements in perioperative care may decrease complications and improve vascular patient outcomes.

Office-based endovascular suite is safe for most procedures.

OBJECTIVE: This study was conducted to identify the safety of endovascular procedures in the office endovascular suite and to assess patient satisfaction in this setting. METHODS: Between May 22, 2007, and December 31, 2012, 2822 patients underwent 6458 percutaneous procedures in an office-based endovascular suite. Demographics of the patients, complications, hospital transfers, and 30-day mortality were documented in a prospective manner. Follow-up calls were made, and a satisfaction survey was conducted. Almost all dialysis procedures were done under local anesthesia and peripheral arterial procedures under conscious sedation. All patients, except those undergoing catheter removals, received hydrocodone and acetaminophen (5/325 mg), diazepam (5-10 mg), and one dose of an oral antibiotic preprocedure and three doses postprocedure. Patients who required conscious sedation received fentanyl and midazolam. Conscious sedation was used almost exclusively in patients having an arterial procedure. Measurements of blood urea nitrogen, creatinine, international normalized ratio, and partial thromboplastin time were performed before peripheral arteriograms. All other patients had no preoperative laboratory tests. Patients considered high risk (American Society of Anesthesiologists Physical Status Classification 4), those who could not tolerate the procedure with mild to moderate conscious sedation, patients with a previous bad experience, or patients who weighed >400 pounds were not candidates for office based procedures. RESULTS: There were 54 total complications (0.8%): venous, 2.2%; aortogram without interventions, 1%; aortogram with interventions, 2.7%; fistulogram, 0.5%; catheters, 0.3%; and venous filter-related, 2%. Twenty-six patients required hospital transfer from the office. Ten patients needed an operative intervention because of a complication. No procedure-related deaths occurred. There were 18 deaths in a 30-day period. Of patients surveyed, 99% indicated that they would come back to the office for needed procedures. CONCLUSIONS: When appropriately screened, almost all peripheral interventions can be performed in the office with minimal complications. For dialysis patients, outpatient intervention has a very low complication rate and is the mainstay of treatment to keep the dialysis access patent. Venous insufficiency, when managed in the office setting, also has a low complication rate. Office-based procedural settings should be seriously considered for percutaneous interventions for arterial, venous, and dialysis-related procedures.

Single-specialty versus multispecialty vascular surgery group model.

The shift in employment options for vascular surgeons in the current era of major health care reform is being widely debated. After the decision to seek hospital employment or independent practice, the choice of then practicing in a single-specialty or a multispecialty practice remains a difficult decision. Although the trend is toward medium-sized to large-sized groups, only 1.2% of medical practices currently have >11 physicians. Barring the large multispecialty groups, such as Kaiser Permanente, Cleveland Clinic, or Mayo Clinic, most vascular practices are constituted as small groups. Which format prospers will depend on adroit management of financial and intellectual capital and nimbleness in adapting to rapidly changing market conditions. In this report, two practicing vascular surgeons debate the merits of single or multispecialty practice, with a commentary to follow.

Changing practice paradigms: negotiating your future.

There are many recent and ongoing changes in the practice of medicine from a business standpoint as well as in overall practice management. Economic and lifestyle desires have pushed many physicians to a decision point of whether or not to join a large multispecialty group or to sell their practice and become an employee of a hospital system. There are advantages and disadvantages to both options; however, deciding on the most appropriate path for each individual can be a daunting task. At our recent breakfast session at the vascular annual meeting in Chicago, Illinois, in June 2011, we brought to light these topics to try and help enlighten physicians on which option may be right for them. There is no single answer/option that will fit every practice, but discussion for various practice management designs are outlined and critiqued. This article cannot fully discuss each view in the allotted space, but it is designed to encourage thought and discussion among the vascular surgical community as a whole.

Future of vascular surgery is in the office.

OBJECTIVE: The practice of vascular surgery is under pressure from various specialties and payers. Our group started office-based procedures in May 2007. This article reports our study of the effect of this change on our case volume, office revenue, and the financial impact on the health care system. METHODS: Between May 1, 2006, and April 30, 2007 (period 1), and between June 1, 2007, and May 31 2008 (period 2), 3041 and 3351 cases, respectively, were performed. In period 1, only venous cases could be done in the office. Before arteriogram, serum levels of urea nitrogen and creatinine were obtained. The number of percutaneous cases done in the hospital and office setting was analyzed, and revenue was calculated based on the 2008 Medicare fee schedule for our region. Amputation and mortality rates at 30 days were documented. Hospital DRG payment schedule was obtained. RESULTS: In period 1, 670 (22% of total) percutaneous procedures were performed compared with 1502 (44.8%) in period 2, a twofold increase. In period 1, 1.5% of total cases were done in the office compared with 31% in period 2. There was a fivefold increase in revenue from these procedures. No deaths or amputations occurred as a result of procedures performed in the office. No anesthesiologist's expense and minimal preprocedural expenses were incurred. Total payment by Medicare, DRG payment to the hospital, and the physician component were higher in all the cases. CONCLUSIONS: A vascular surgery practice can benefit from office-based procedures. Procedures can be done safely. It results in an increase in the number of percutaneous procedures and revenue with a significant savings to the health care system. Surgeons can control their schedule. Every vascular surgeon should consider doing these procedures in office.

Optimizing your vascular practice: how to communicate with referring doctors, increase referrals, and work with cardiologists and interventional radiologists.

After the fellowship in vascular surgery is completed there is the daunting task of going into practice and succeeding. There are various tools that one can use to succeed in practice and also work closely with other specialists. The key to success is marketing and innovation. Using the two together any vascular surgeon can succeed. Marketing has multiple facets not to be confused with advertising. Total marketing revolves around the surgeon. It involves personal attributes, running of the office, behavior in the hospital, working with other physicians, and using advertising channels. Innovation is required as the art and science of the specialty continues to evolve. Vascular surgeons need to be on the cutting edge of providing latest technology as well as latest methods of delivering care.

Fistulogram after arteriovenous dialysis graft thrombectomy should be mandatory.

The purpose of this study was to determine if fistulogram after prosthetic arteriovenous dialysis graft thrombectomy would reveal underlying lesions, which need correction, and if revision would improve graft patency. One hundred and ninety-two open thrombectomy procedures in 61 patients from January 1, 2000 to July 31, 2005 were reviewed retrospectively. All of the study patients were divided into two groups: In Group I fistulogram was carried out and in Group II no fistulogram was performed. Based on the fistulogram or clinical findings, appropriate intervention was carried out. In Group I, of 99 thrombectomy procedures, a significant lesion was identified and revision was carried out in 77 cases (78%). In Group II, of 93 thrombectomy procedures, a significant lesion was identified and revised in 53 cases (57%). A significant abnormality was more likely to be encountered by routine fistulogram than surgical exploration alone, 78 per cent versus 57 per cent (P < 0.05). Assisted primary patency is significantly increased in Group I and II when revision was performed (4.84 months) compared with when no fistulogram and no revision was performed (2.9 months), P < 0.05. Routine fistulogram after thrombectomy of an arteriovenous dialysis graft increases the likelihood of identifying a significant stenosis. Revision of the graft increases the longevity. We recommend routine use of fistulogram during thrombectomy.