Vitis Vinifera Seed Extract Versus Micronized Purified Flavonoid Fraction for Patients with Chronic Venous Disease: A Randomized Noninferiority Trial.

BACKGROUND: Venoactive drugs (VADs) based on Vitis vinifera extract are widely used in Korea. However, studies on the clinical effects and head-to-head comparisons with other groups of VADs are limited. This trial aimed to evaluate whether Vitis vinifera seed extract was noninferior to the micronized purified flavonoid fraction (MPFF) in relieving venous symptoms and improving quality of life in patients with chronic venous disease. METHODS: In this double-blind prospective randomized trial, patients from 13 hospitals, who were diagnosed with venous incompetence by duplex ultrasound and classified as clinical class 1, 2, or 3 in the Clinical, Etiological, Anatomical, and Pathophysiological classifications were enrolled. The primary outcome was the change in the Chronic Venous Disease Quality of Life Questionnaire (CIVIQ-20) score at 8 weeks from baseline. Secondary outcomes included changes in the Aberdeen Varicose Vein Questionnaire, visual analog scale, and Venous Clinical Severity Score at 4 and 8 weeks from baseline. Moreover, the change in leg circumferences was measured at 8 weeks and compared to baseline. RESULTS: In total, 303 patients were enrolled and randomly assigned to receive either Vitis vinifera seed extract (n = 154) or MPFF (n = 149). The CIVIQ-20 scores at 8 weeks were significantly reduced compared to those at baseline in both groups. No significant intergroup difference in the change of CIVIQ-20 at 8 weeks from baseline was observed (-8.31 ± 14.63 vs. -10.35 ± 14.38, P = 0.29, 95% confidence interval -1.65 to 5.72). The lower limit of the 95% confidence interval was within the predefined noninferiority margin of 6.9. Furthermore, the Aberdeen Varicose Vein Questionnaire, visual analog scale, and Venous Clinical Severity Score scores significantly decreased at 4 and 8 weeks after randomization compared with baseline in both groups. No significant differences were observed in the reduction of each score between groups. The calf circumference measured at 8 weeks was significantly reduced compared to that at baseline in patients receiving Vitis vinifera seed extract. CONCLUSIONS: Vitis vinifera seed extract was noninferior to MPFF in relieving venous symptoms and improving the quality of life in patients with chronic venous disease.

Predicting factors for early failure of vascular access in hemodialysis patients.

Purpose: This study aimed to investigate the incidence of early failure of vascular access for hemodialysis, and determine which factors measured in duplex ultrasound study could predict early failure. Methods: We performed a retrospective review of patients who underwent arteriovenous fistula (AVF) or arteriovenous graft (AVG) creation for hemodialysis between September 2019 and January 2023. Early failure was defined as any event that required surgical or endovascular intervention within 6 months following AVF or AVG creation. Results: A total of 189 patients were included. Early failure occurred in 36 patients (19.0%), which included 22 AVFs and 14 AVGs. In the patients who underwent AVF, the preoperative venous diameter, postoperative venous and arterial diameters, and flow volume of AVF all were significantly smaller in the early failure group compared to the patent group. In AVG, the preoperative venous diameter was the only parameter that differed between the 2 groups. A sonographic score was defined based on these factors. In a multivariable analysis, male sex, a previous history of AVF or AVG creation, and sonographic score were found to be significantly associated with early failure. The postoperative venous diameter in AVF and the preoperative venous diameter in AVG were highly predictive of early failure (areas under the curves 0.92 and 0.82, respectively). Conclusion: Venous diameter measured 6 weeks following AVF operation and preoperative venous diameter in AVG were highly predictive of early failure among the duplex ultrasound parameters. Surveillance strategies in the early phase following vascular access creation can be based on these factors.

Association of immunologic findings of atheromatous plaques with subsequent cardiovascular events in patients with peripheral artery disease.

Patients with peripheral artery disease (PAD) have a higher risk of cardiovascular events. We examined the histology of atheromatous plaques in the femoral artery and investigated their association with subsequent cardiovascular events in patients with PAD. Patients who underwent femoral artery endarterectomy between March 2010 and January 2021 were included. We analyzed the expression of myeloperoxidase (MPO), citrullinated histone, and programmed cell death ligand 1 (PD-L1) in femoral artery plaques by immunohistochemistry. Data on the subsequent occurrence of major adverse cardiovascular events (MACEs), major adverse limb events (MALEs), and all-cause mortality were retrospectively collected. A total of 37 patients were included. The median age was 71 (range, 42-90) years, and 25 patients (67.6%) were male. During the median follow-up of 24 months, 10 patients experienced MACEs and 16 patients had MALEs. Patients with MACEs had a higher number of MPO-stained cells (p = 0.044) and lower PD-L1 staining intensity (p = 0.021) in atheromatous plaques compared with those of patients with a stable prognosis. When the patients were grouped according to the immunologic score based on the MPO-stained cell number and PD-L1 staining intensity, those with a higher score had a significantly higher cumulative risk of MACEs (p = 0.014). The immunologic profile of excised peripheral artery plaques may be associated with future cardiovascular events in patients with PAD.

The immunologic phenotype of thrombi is associated with future vascular events after cerebral infarction.

BACKGROUND: Thrombi retrieved from patients with acute ischemic stroke may contain prognostic information. OBJECTIVE: To investigate the relationship between the immunologic phenotype of thrombi and future vascular events in patients with a stroke. METHODS: This study included patients with acute ischemic stroke who underwent endovascular thrombectomy at Chung-Ang University Hospital in Seoul, Korea, between February 2017 and January 2020. Laboratory and histological variables were compared between patients with and without recurrent vascular events (RVEs). Kaplan-Meier analysis followed by the Cox proportional hazards model was used to identify factors related to RVE. Receiver operating characteristic (ROC) analysis was conducted to evaluate the performance of the immunologic score by combining immunohistochemical phenotypes to predict RVE. RESULTS: A total of 46 patients were included in the study with 13 RVEs (mean±SD age, 72.8±11.3 years; 26 (56.5%) men). Thrombi with a lower percentage of programmed death ligand-1 expression (HR=11.64; 95% CI 1.60 to 84.82) and a higher number of citrullinated histone H3 positive cells (HR=4.19; 95% CI 0.81 to 21.75) were associated with RVE. The presence of high-mobility group box 1 positive cell was associated with reduced risk of RVE, but the association was lost after adjustment for stroke severity. The immunologic score, which consists of the three immunohistochemical phenotypes, showed good performance in predicting RVE (area under the ROC curve, 0.858; 95% CI 0.758 to 0.958). CONCLUSIONS: The immunological phenotype of thrombi could provide prognostic information after stroke.

Spontaneous Celiac Artery Dissection with Splenic Infarction: A Report of Two Cases.

Spontaneous isolated celiac artery dissection (SICAD) is a rare condition that is characterized by sudden onset abdominal pain, typically occurring in middle-aged men. Although its clinical course is mostly benign, it may progress to true lumen occlusion. No established therapeutic guidelines are available for SICAD associated with splenic infarction. This report describes two patients who presented with sudden onset abdominal pain and were diagnosed with SICAD with splenic infarction based on computed tomography (CT) findings. Patients were treated with bowel rest and anticoagulants. After a week of medical therapy, the abdominal pain resolved. Follow-up CT revealed no progression of the dissection flap. The patients received oral anticoagulants for 3 months and did not experience any symptom recurrence. Medical therapy with anticoagulants may be considered for patients with SICAD and splenic infarction. Associated splenic infarction itself is not an indication for endovascular or surgical intervention for SICAD.

Treatment failure after rotational atherectomy and balloon angioplasty in recurrent cystic adventitial disease of the popliteal artery: a case report.

Cystic adventitial disease (CAD), which usually affects the popliteal artery, is a rare vascular condition in which fluid accumulates in the sub-adventitial layer, compressing the lumen. Historically, surgical treatment is preferred over endovascular or minimally invasive techniques, due to its lower recurrence rates. Here, the case of a 67-year-old male patient, in whom rotational atherectomy was performed for recurrent CAD following surgical cyst excision and patch angioplasty is reported. The patient's symptoms recurred one day after the rotational atherectomy procedure and repeat computed tomography angiography showed recurrence of the disease. Due to gradual worsening of the condition during 8 months of follow-up, left distal femoral artery to popliteal artery (below-the-knee) bypass surgery was performed using an ipsilateral reversed great saphenous vein graft. Follow-up has continued for 2 years without complications or requirement of additional treatment. This novel case is the first report of atherectomy attempted for recurrent CAD that led to an early recurrence. Our experience emphasises that additional surgical approaches should be selected over endovascular procedures for treating recurrent CAD.

Flat Pattern Peaks of Tacrolimus Absorption and Associated Pharmacogenomic Variants in Kidney Transplantation Recipients.

BACKGROUND: Tacrolimus is the most commonly used immunosuppressive drug in solid organ transplantation. After administering a conventional twice-daily dose of tacrolimus, peak levels were achieved within the first 1.5 to 2 hours. A group of patients showed different early absorption phase of tacrolimus after kidney transplantation. METHODS: Trough(C0) and 1.5-hour blood levels (C1.5) of tacrolimus were measured in 95 kidney transplantation recipients. Patients with a C1.5/C0 < 1.5 and > 1.5 were defined as those having flat pattern peaks and as controls, respectively. Transplantation outcomes were compared between the groups. Whole exome sequencing was performed to investigate the genetic susceptibility to flat pattern peaks. RESULTS: Twenty-eight patients showed flat pattern peaks. The mean C1.5/C0 values were 1.13 ± 0.22 and 3.78 ± 1.25 in the flat pattern peak and control groups, respectively. In multivariate analysis, flat pattern peak was an independent risk factor for biopsy-proven acute rejection (BPAR) and/or borderline change (P = 0.014). Patients having flat pattern peaks showed significantly lower post-transplant 36-month estimated glomerular filtration rate (P = 0.001). Two single nucleotide variants in ABCB1 genes, rs1922242 and rs2235035, were associated with flat pattern peaks (P = 0.019 and P = 0.027, respectively). CONCLUSION: Both of C1.5 and C0 should be measured to distinguish the patients showing unique initial absorption. A C1.5/C0 ratio lower than 1.5 was associated with an increased risk of BPAR and/or borderline change. Single nucleotide variants s in ABCB1 gene might influence the flat pattern peaks of tacrolimus absorption.

Clinical presentation of isolated calf deep vein thrombosis in inpatients and prevalence of associated pulmonary embolism.

OBJECTIVE: Controversy exists regarding the clinical significance and optimal treatment of isolated calf deep vein thrombosis (DVT). In the present study, the clinical presentation of isolated calf DVT and the association of isolated calf DVT with pulmonary embolism (PE) in hospitalized patients were investigated. METHODS: A total of 1435 hospitalized patients had undergone whole leg duplex ultrasound between January 2018 and June 2020. Isolated calf vein DVT was diagnosed in 135 of these 1435 patients. RESULTS: The soleal vein was the most frequently involved (52.6%). Thrombus was detected only in the axial veins in 57 patients (42.2%), muscular veins in 46 patients (34.4%), and both axial and muscular veins in 32 patients (23.7%). Of the 135 patients, 44 (32.6%) had undergone recent orthopedic surgery, 31 (23.0%) had active cancer, and 22 (16.3%) had a history of recent stroke. The reasons for duplex ultrasound examination were leg edema and/or pain for 57 patients (42.2%), the diagnosis of PE for 33 (24.4%), and an elevated D-dimer level for 27 patients (20.0%). For 16 patients (11.9%), DVT had been diagnosed as an incidental finding on imaging studies performed for other purposes. Of the 135 patients, 96 (71.1%) had received anticoagulation therapy. Concurrent PE was diagnosed in 45 patients (33.3%), 14 of whom had had lesions in the main pulmonary artery. Of the 45 patients with concurrent PE, 35 had not experienced leg edema and/or pain. Recurrent venous thromboembolism was observed in four patients (3.0%) at a mean follow-up of 15.5 ± 12.7 months. CONCLUSIONS: In the present study, isolated calf DVT was associated with a high prevalence of PE in the hospitalized patients. Patients with isolated calf DVT, even without leg edema and/or pain, could have concurrent PE. Anticoagulation therapy should be considered for inpatients with isolated calf DVT. The muscular veins were frequently involved and, thus, should be thoroughly evaluated with imaging studies.

A Popliteal Vein Aneurysm Accompanied by Lower Persistent Sciatic Vein.

Popliteal venous aneurysms (PVAs) are rare. Surgical treatment is recommended because of the risk of deep vein thrombosis and fatal pulmonary embolism. A persistent sciatic vein (PSV) is also a rare anomaly. We report a case of a PVA accompanied by a lower PSV. A 70-year-old man was admitted due to left leg heaviness. He had undergone ablation of both great saphenous veins 6 years prior to the admission. Duplex ultrasound showed a PVA on his left leg, which was 3.2 × 2.4 cm in size. The patient was treated with tangential aneurysmectomy with lateral venorrhaphy. His symptom gradually resolved. He received warfarin at a therapeutic range for 3 months. Duplex ultrasound at 6 months later showed no evidence of any recurrent aneurysm or venous reflux. His follow-up has revealed no complications for 18 months. Surgical treatment and perioperative therapeutic anticoagulation are recommended for treating PVAs. Tangential aneurysmectomy with venorrhaphy is the most common and the simplest surgical method.

Klotho as a potential predictor of deceased donor kidney transplantation outcomes.

PURPOSE: Klotho is an antiaging factor mainly produced by renal tubular cells. Klotho is reportedly decreased in an animal model of acute kidney injury and patients with chronic kidney disease. However, information on Klotho expression after kidney transplantation is limited. We analyzed the correlation between donor Klotho expression and clinical outcomes of kidney transplantation. METHODS: Sixty patients who underwent deceased donor kidney transplantation between March 2015 and October 2017 were enrolled. Serum and tissue Klotho expression levels were measured by enzyme-linked immunosorbent assay and immunohistochemistry, respectively. Graft function was assessed by estimated glomerular filtration rate (eGFR). RESULTS: Patients were divided into 2 groups according to donor Klotho expression in renal tissues. A greater improvement in eGFR was observed at 1 week after transplantation in patients receiving kidneys with higher Klotho expression (47.5 ± 21.9 mL/min/1.73 m2 vs. 63.9 ± 28.2 mL/min/1.73 m2, P = 0.030). Patients were also classified into 2 groups according to donor serum Klotho level. There was a tendency for a higher eGFR at 12 months after transplantation in patients receiving kidneys from donors with a higher Klotho level (51.0 ± 18.0 mL/min/1.73 m2 vs. 61.2 ± 16.5 mL/min/1.73 m2, P = 0.059). When subgrouped into patients with or without biopsy-proven acute rejection, 12-month eGFR remained higher in patients receiving kidneys from donors with higher serum Klotho. CONCLUSION: Our data demonstrated that donor tissue expression of Klotho correlated with early recovery of eGFR after kidney transplantation. Donor serum Klotho level tended to be associated with posttransplant 12-month eGFR. Donor Klotho expression might be a new predictor for deceased donor kidney transplantation outcome.

Outcome of ClosureFAST radiofrequency ablation for large-diameter incompetent great saphenous vein.

PURPOSE: There is limited data on the outcomes of radiofrequency ablation (RFA) for large diameter saphenous veins. This study aimed to determine whether the large-diameter great saphenous vein (GSV) affected closure rate, complications, and clinical and quality of life (QoL) improvement. METHODS: From January 2012 to September 2016, a total of 722 limbs were treated with ClosureFAST RFA in a single center. Patients were divided into 2 groups according to the vein diameter measured 3 cm below the saphenofemoral junction (group A ≤ 12 mm, group B > 12 mm). Vein closure was evaluated with duplex scan at 3-5 days, 1, 3, 6, and 12 months postoperatively. The incidence of complications, improvements in symptoms (measured by the Venous Clinical Severity Score [VCSS]) and QoL (measured by the Aberdeen Varicose Vein Symptom Severity Score [AVSS]) were evaluated. RESULTS: Groups consisted of 663 GSVs in group A (mean diameter, 6.00 ± 1.74 mm) and 59 in group B (mean diameter, 13.17 ± 1.28 mm). Vein closure rates at 12 months were 98.9% in group A and 100% in group B (P = 0.428). There was no significant difference in the incidence of complications. Both groups showed marked improvements in the VCSS and the AVSS with no significant differences. CONCLUSION: For large-diameter veins, RFA showed comparable outcomes in terms of closure rate, complications, clinical and QoL improvements.

Timing of referral for vascular access for hemodialysis: Analysis of the current status and the barriers to timely referral.

INTRODUCTION: Current guidelines recommend the placement of vascular access 6 months before the anticipated start of hemodialysis therapy; however, many patients start hemodialysis using a central venous catheter. We investigated the timing of referral for vascular access, the vascular access type at hemodialysis initiation, and the barriers to a timely referral. METHODS: The study involved a retrospective review of 237 patients for whom the first vascular access for hemodialysis was created between January and November 2017. RESULTS: Among the 237 patients, 58.2% were referred before hemodialysis initiation, while 41.8% were referred after hemodialysis initiation. Among the 138 patients, 55, 59, and 24 patients were referred more than 6 months, between 2 and 6 months, and within 2 months before hemodialysis initiation, respectively. Within these subgroups, 3.6%, 10.2%, and 75.0% patients underwent hemodialysis initiation with a central venous catheter, respectively. Among the 99 patients referred after hemodialysis initiation, the reasons for late referral were as follows: unexpected rapid progression of kidney disease (n = 23), noncompliance (n = 21), late visit to the nephrologist (initial visit within 2 months of hemodialysis initiation; n = 14), change of treatment strategy from peritoneal dialysis or transplants (n = 9), and unknown reasons (n = 32). CONCLUSION: Only 23% of patients were referred for vascular access 6 months before the anticipated hemodialysis therapy. In addition, 53% of patients initiated hemodialysis with a central venous catheter. Avoidance of catheter insertion was mostly successful in patients referred 2 months before hemodialysis initiation. The most common modifiable barrier to the timely referral was noncompliance.

Effect of Inflow Arterial Calcification on Arteriovenous Fistula Maturation.

BACKGROUND: The aim of this study is to investigate the effect of preexisting calcification in the inflow artery on maturation and flow volume of an arteriovenous fistula (AVF). METHODS: Patients who underwent AVF creation for hemodialysis were prospectively recruited between March and November 2017. On preoperative duplex ultrasound, calcification in the arterial media within 5 cm of the planned anastomosis area was assessed. Clinical maturation was defined as the successful use of the fistula for ≥75% of the dialysis sessions during a month within 6 months after surgery. Radiological maturation was defined as a venous diameter of ≥0.4 cm and a flow volume of ≥500 mL/min. Flow volumes of the inflow artery and the cephalic vein were measured at 6 and 12 weeks after AVF creation. RESULTS: Eighteen patients with calcification and 29 patients without calcification were enrolled in this study. There was no significant difference in the clinical and radiological maturation between the groups. The flow volume of the inflow artery, measured at 6 weeks postoperatively, was significantly higher in the noncalcification group than in the calcification group (P = 0.042). The flow volume of the inflow artery in the noncalcification group was increased at 12 weeks postoperatively (P = 0.091). Flow volume of the vein was higher in the noncalcification group than in the calcification group, although it did not reach statistical significance. CONCLUSIONS: In conclusions, preexisting arterial calcification did not adversely affect the AVF maturation. However, arterial calcification correlated with the flow volume of the inflow artery of AVF.

Treatment Strategies for Cephalic Arch Stenosis in Patients with Brachiocephalic Arteriovenous Fistula.

BACKGROUND: Cephalic arch is one of the sites most susceptible to stenosis in brachiocephalic arteriovenous fistula (BCAVF). We performed a retrospective study to identify the incidence of cephalic arch stenosis (CAS) in BCAVF, to compare the patency of percutaneous transluminal balloon angioplasty (PTA) with that of cephalic vein transposition (CVT), and to establish the optimal treatment strategy for CAS. METHODS: Between January 2011 and June 2016, 462 patients underwent BCAVF creation. CAS was defined as >50% stenosis at the confluence of the cephalic and axillary veins on ultrasonography. Treatment was planned for clinically significant CAS, which was defined as >25% reduction in flow volume compared to previous examination, elevation of venous pressure, delayed puncture site hemostasis, and/or acute thrombotic occlusion. RESULTS: Seventy-seven (16.7%) patients had CAS and 42 of them (54.5%) were treated for clinically significant CAS. PTA was performed in 36 patients (85.7%), and CVT was done in 6 patients (14.3%) as the initial treatment. Nine patients underwent CVT after PTA, resulting in a total of 15 patients treated with CVT. Investigation of the patency of the 36 cases of PTA and 15 cases of CVT revealed that primary-assisted patency rates at 6 and 12 months were 68.2% and 57.3% for PTA and 100.0% and 87.5% for CVT, respectively (P = 0.038). Secondary patency rates at 6 and 12 months were 72.0% and 56.9% for PTA and 100% and 100% for CVT, respectively (P = 0.010). The median intervention rate was 2.5 interventions per access-year in the 36 cases treated with PTA and 1.5 interventions per access-year in the 15 cases treated with CVT. CONCLUSIONS: CAS is a common cause of BCAVF dysfunction, and careful surveillance is warranted. CVT should be considered for treatment of CAS to achieve better long-term patency with fewer reinterventions.

Successful Endovascular Treatment of a Ruptured Popliteal Artery Aneurysm in a Patient with Behcet Disease.

PURPOSE: Arterial involvement of Behcet disease is often found in the form of a rapidly expanding aneurysm. We report a case of successful treatment of a ruptured popliteal artery aneurysm with a stent-graft insertion. CASE REPORT: A 55-year-old male patient was admitted because of pain and swelling in the right leg that had persisted for 15 days. Computed tomography (CT) angiography showed a contained rupture of a large right popliteal artery aneurysm. Laboratory tests showed elevated erythrocyte sedimentation rate (ESR) and C-reactive protein level. The patient had a history of recurrent oral and genital ulceration, folliculitis, and erythema nodosum. He was diagnosed as having Behcet disease with arterial involvement. After 5 days of immunosuppressant medications, the ESR decreased. A 7 mm × 10 cm stent graft was inserted into the right popliteal artery, and completion angiography showed the successfully excluded aneurysm. His symptoms were gradually relieved. The stent graft was patent on CT angiography 15 months after the procedure. He has been followed up for 16 months with dual antiplatelet agents and immunosuppressive medications. CONCLUSIONS: Endovascular therapy for peripheral aneurysms in patients with Behcet disease is safe and minimally invasive. Careful follow-up to monitor disease progression is necessary.

How to treat arteriovenous graft infection: total versus partial graft excision.

INTRODUCTION: Arteriovenous graft (AVG) infection can result in life-threatening sepsis and loss of vascular access. A retrospective study was performed to establish an appropriate treatment strategy for AVG infection. METHODS: A total of 50 cases of AVG infection were treated between January 2005 and June 2016. The surgical methods used were total graft excision (TGE) (n = 34), or partial graft excision (PGE) with interposition graft (n = 16). RESULTS: Infection was noted at a puncture site (n = 22), a prior incision for surgery or endovascular therapy (n = 20), and abandoned (currently unused) grafts (n = 5). Infection occurred within 1 month after AVG creation (n = 1), or any intervention (n = 14), and more than 1 month after creation or intervention (n = 35). Simultaneous remote infection was identified in 7 patients, 2 of whom underwent an operation for infective endocarditis and spondylitis. After PGE, 5 patients (5/16, 31.2%) having recurrent infection were treated with further graft excision; however, no patient showed life-threatening complications. After TGE, a central venous catheter (CVC) was inserted and used for a median period of 90 days. Among 34 patients who underwent TGE, new vascular access was created in 18 patients at a median period of 2 months later, and 12 patients continued to use a CVC until last follow-up or death. CONCLUSIONS: PGE could be a treatment option for AVG infection to achieve both infection eradication and vascular access preservation in selected patients. Because of a higher risk of recurrent infection, sufficient surgical removal and careful postoperative management are warranted.

Improvements of deep vein reflux following radiofrequency ablation for saphenous vein incompetence.

Objectives The aim of this study was to describe the changes of deep vein reflux after radiofrequency ablation for great saphenous vein incompetence. Method The data on 139 limbs which were treated with radiofrequency ablation for great saphenous vein incompetence were prospectively collected and reviewed. Results Deep vein reflux was present in 43 of 139 limbs (30.9%). There were no significant differences in the rate of successful closure, the incidence of procedure-related complications, and the improvements of symptoms and quality of life between the limbs with or without deep vein reflux. With a mean follow-up of 5.9 months, the peak reflux velocity and duration of reflux were improved in all limbs with deep vein reflux and it was completely corrected in 13 limbs (30.2%) after radiofrequency ablation. Conclusions The presence of deep vein reflux does not affect the treatment outcomes of radiofrequency ablation for great saphenous vein incompetence and is improved in all patients. Deep vein reflux is not a barrier to performing radiofrequency ablation.