Endovascular treatment options in central venous stenosis and occlusion: Angioplasty or Stent ?

Objectives: The purpose of this study was to compare the patency rate outcomes and efficacy of percutaneous transluminal angioplasty (PTA) versus percutaneous transluminal stenting (PTS) for the treatment of central vein stenosis and occlusion in hemodialysis patients. Materials and Methods: A total of 71 chronic hemodialysis patients (36 males, 35 females) with 142 events of central venous stenosis or occlusion underwent 109 endovascular interventions between March 2013 and June 2018. The clinical follow-up of the patients was performed with control venography at 1, 3, and 6 months, and then at 6-month intervals for asymptomatic patients. Results: PTA was applied to 45 patients and PTS to 26 patients during the study period. At 3, 6,12 and 24 months, primary patency rates were 97.74%, 88.23%, 73.76% and 50.76% respectively in the PTA group and 96.23%, 92.34%, 65.96% and 47% in the PTS group. Assisted primary patency at 3, 6, and 12 months was 97.73%, 90.76%, and 75.92% respectively in the PTA group and 96.25%, 84.38%, and 79.87% in the PTS group. No statistically significant difference was determined between the groups in respect of primary and assisted patency rates (p=0.216, p=0.121). The average number of interventions in the PTS group (2.62± 1.23) was significantly higher than that in the PTA group (1.43±0.62). Conclusion: Endovascular treatment is a safe and effective method in the management of central vein occlusion. PTS does not result in longer patency in the treatment, but conversely incurs greater costs and necessitates more interventions to provide patency. Therefore, PTS should only be preferred for PTA-resistant lesions or concurrent lesions.


Introduction
Central vein stenosis and occlusion is a frequently seen issue in hemodialysis patients . 1,2 The most common predisposing factor in central vein stenosis and occlusion has been reported to be prior central vein catheterization. [3][4][5][6] Open surgical treatment and endovascular approach are the two main treatment methods in the management of central venous occlusive diseases. However, exposure of the chest and repair of these deep thoracic veins makes the surgical options more difficult and increases mortality rates, thereby limiting surgical procedures. Therefore endovascular treatment is a prominent method in central vein occlusive disease which offers a less invasive and more comfortable method for the patients compared to open surgical methods. 2 Angioplasty and stent placement are the two main current treatment options in the endovascular approach.
The purpose of this study was to compare the patency rate outcomes and efficacy of percutaneous transluminal angioplasty (PTA) versus percutaneous transluminal stenting (PTS) for the treatment of central vein stenosis and occlusion. subclavian stenosis. Patients with >50% stenotic segments were included in the study and stenosis ranged from 70% to 95%. In addition to chronic renal failure, the demographic data and comorbidities were evaluated in both groups ( Table 1). The study was conducted in accordance with the principles of the Declaration of Helsinki. Ethical approval was obtained from our hospital's ethical committee for this study (KA19/270).

Treatment Procedure
The endovascular procedure was started after injection of a local anesthetic to the puncture site of the axillary vein under US guidance and a 7F sheath was deployed. The access site was selected on the same side as a stenotic or occluded vein. All patients were administered 2.500 U heparin at the beginning of the procedure and control venography was performed to demonstrate the stenosis or occlusions ( Figure 1A). The procedure continued with the 0.035 guidewire (Terumo, Europa) was passed over the stenotic or occluded segment of the vein with aid of manipulations of the 5F catheter (Kumpe, Cook) under the road map guidance. If resistance prevented passing the stenotic or occluded segment, the guidewire was exchanged for a stiff guide (Amplatz super Stiff, Boston Scientific) wire to enable better advancement. Balloon angioplasty was performed in the stenotic or occluded segments with balloon diameters ranging from 8 to 18 mm at burst pressures of 5 -18 atm ( Figure.1B). The balloon diameter selected was 1-2 mm greater than the adjacent normal vein diameter on venography. The indications for stent placement after PTA were as follows; complete recoil, residual stenosis, presence of collateral veins and recurrent stenosis/occlusions to which two or more interventions were applied in a 2-month period. The stent diameter selected was 1 mm greater than or equal to the diameter of the balloon and stent length was determined by the extent and location of the lesion. Self-expandable Nitolol stents were used, ranging from 8 to 14 mm in diameter and 40-80 mm in length. After the intervention, control venography was performed to demonstrate the adequate venous flow ( Figure 1C). Hemostasis was achieved with manual compression (approximately 5-10 min). All patients were discharged after 2 hours of observation in the angiography unit. Technical success was defined as the provision of flow without significant stenosis or the disappearance of collateral veins. The clinical follow-up of the patients was performed with control venography at 1, 3, and 6 months and at 6-month intervals thereafter for asymptomatic patients. If there was a symptom recurrence between these intervals, control venography was also performed. Color Doppler sonography was not used for the follow-up imaging as it is not sufficient for the visualization of central veins and has lower sensitivity than venography in central vein stenosis. Repeat angioplasty procedures were performed in cases with >50% stenosis in all symptomatic and asymptomatic patients.
The primary patency and assisted primary patency rates were evaluated for all the patients in the PTA and PTS groups. Primary patency was defined as the interval between the day of the first intervention to adequate flow in the vein until the occurrence of stenosis or occlusion. Assisted primary patency was defined as patency during the interval between the primary intervention and the time of a subsequent intervention required due to stenosis or occlusion.

Study Outcomes
The primary objective of this study was to assess the technical success of the recanalization of the stenotic/occluded central veins. A secondary aim was to compare the patency rate outcomes of PTA versus PTS.

Statistical Analysis
Data obtained in the study were analyzed statistically using IBM SPSS statistics software version 23 (IBM Corp, USA). Descriptive statistics were reported as mean and standard deviation values for variables with normal distribution and median (minimum-maximum) values for variables not conforming to normal distribution.
Kaplan Meier analysis was applied to evaluate Primary and Assisted patency rates in both the PTA and PTS groups. The Log rank test was used to compare patency rates.       disease, the open surgical method, which is one of the current treatment options, has been shown to have satisfactory patency rates of 80-85% in 1 year, but also to have significant morbidity rates due to the location of vascular structures in the chest. 11,12 Therefore, endovascular treatment of central venous diseases began to be discussed at the threshold of advances in endovascular treatment towards the mid-1980s . 13 The advantages of the endovascular approach are that it can be performed under local anesthesia, it is more comfortable for the patient and has a shorter hospitalization period when compared to open surgery. In previous studies, endovascular treatment of central venous disease has been reported two main categories; angioplasty with or without stenting after failed angioplasty or due to recurrent stenosis and stenting as the initial therapy. Many articles have been published using primary angioplasty as the initial treatment method in central vein disease, and these have reported primary patency rates ranging from 20% to 77% and assisted patency ranging from 63% to 82%. [14][15][16][17] The highest PTA patency rate (The primary and secondary patency rates at 12 months were 77% and 88% respectively) was reported in a study by Ozyer et al. with stenting added to the initial balloon angioplasty procedure to achieve long-term patency as was the procedure in the current study. 17 The main cause of low patency rates in other studies (Nael K  was an evolution in management at that time, and the 1-year patency rate was reported as 56% . 18 There have been many subsequent articles published about the use of wall stents in central venous disease treatment and patency rates have been reported as ranging from 42% to 84% at 6 months but < 31% at 12 months . [19][20][21] However, in many previous studies, the benefit of stenting on vessel patency has not been well demonstrated.

Results
Two studies which compared PTA and PTA with stenting by Quin et al and Bakken at al reported that primary patency rates were equal in each treatment method, as was determined in the current study . 15,21 In only one article published by Ozyer et al, were primary patency rates reported to be higher in cases treated with balloons instead of primary stenting. 17 In the light of the information in these studies, stenting was applied in the current Ankara Med J, 2020;(1):242-250 // 10.5505/amj.2020.42103 248 study if there was >50% stenosis after initial PTA and recurrent stenosis that required intervention every 1 or 2 months. In our study, we used Nitinol stents in case of stenting. Some studies have shown no difference in patency rates with the use of wall stents and nitinol stents; whereas others have stated that the patency rates of nitinol stent are longer than those of wall stents. A study conducted by Dheeraj K. et al reported 1-year patency of 66. 7% with nitinol stent for central vein occlusion in a small group of patients . 22 In our study, PTS primary patency rates at 6 and 12 months were 92.34 and 65. 96 % respectively. In addition, it has been reported in previous studies that migration and foreshortening is seen with the use of wall stents in central venous segments . 18,23 Nitinol stents are structured to provide minimum foreshortening . 24 In the current study group, 2 cases of foreshortening were observed but neither required reintervention. Only one stent fracture was observed in a subclavian vein during the follow-up. This complication was thought to have occurred because of the compression between the clavicle and the great vessels. In this patient, a second stent was inserted to provide vessel patency.
A major issue in central vein diseases is frequent recurrent stenosis after treatment. Therefore; the treatment of central venous diseases usually requires more than one intervention. The outcomes of this study showed no significant difference between the PTS and PTA groups in respect of the 12-month primary and assisted primary patency rates. Choosing a stent as a primary intervention does not result in longer patency, but conversely entails additional costs and necessitates more interventions to provide patency. Therefore, PTS should only be preferred in cases with PTA-resistant lesions or frequent concurrent stenosis and occlusions.

Declaration of Conflicting Interests:
The authors declare that they have no conflict of interest.
Financial Disclosure: No financial support was received.