This study analyzed eight Taiwanese patients with IVCT. To the best of our knowledge, this is the first report that has examined the presentation and characteristics of IVCT in Taiwanese patients.
Based on the pathogenesis of VTE, IVCT could be caused by congenital or acquired abdominal pathophysiological changes combined with the presence of various prothrombotic factors. Venous thrombus formation tends to increase if congenital IVC anomalies are present. A recent systemic review reported that congenital IVC anomalies, with a weighted prevalence of 6.8%, could lead to a 50- to 100-fold increase in the risk of DVT [8]. However, no congenital IVC anomaly was detected in our cohort, as only a limited number of adult cases were enrolled.
With respect to IVCT-affiliated VTE manifestation, all our patients had DVT, while five (62.5%) also had PE. Typical clinical features of IVCT include bilateral lower extremity DVT, scrotal swelling, unexplained back pain, pelvic pain, and renal failure [9–12]. Most of these features were present in this cohort. When coexisting with predisposing factors, such as a congenital IVC anomaly or prior placement of an unretrieved IVC filter, these classic presentations strongly indicate the probability of IVCT. Furthermore, four of our patients presented with bilateral lower extremity swelling (due to DVT) simultaneously with abdominal wall superficial venous dilatation. This is a pathognomonic manifestation of IVCT, based on our experience and the reports of other studies [9]. In addition, six patients developed collateral circulation within the abdomen, indicating the chronically long-standing nature of their condition.
Various risk factors for VTE were observed in our patients. Specifically, two patients developed IVCT after an IVC filter implantation was not removed. The complication did not occur in the other two patients whose filters were later retrieved. Our data confirmed the emerging risk of IVCT as a potential complication after an un retrieved IVC filter placement in Taiwanese patients. This corresponds to accumulating evidence from other Asian countries with a reported long-term lower risk of VTE [13–15]. Our experience also indicates that the identification of IVCT in Taiwan should no longer be an under-recognized issue. The incidence could be raised due to the potential hazards of the increasing use of IVC filters.
The effectiveness of IVC filters in preventing PE in patients with VTE remains controversial and inconclusive. According to the PREPIC study [16], an IVC filter was shown to have the potential benefit of protecting against short-term PE (at 12 days, 1.1% with PE in the filter group versus 4.8% in the no-filter group, p = 0.03). However, it had a higher risk of symptomatic DVT in the long term (at 2 years, 20.8% in the filter group vs. 11.6% in the no-filter group, p = 0.02). However, according to the study, there was no difference in the mortality rates during the 8-year follow-up [17]. Furthermore, increased mortality and incidence of subsequent DVT were observed in patients with IVC filters, according to the American Society of Hematology (ASH) 2020 guidelines for the management of venous thromboembolism [18]. This contained an evaluation of seven systemic reviews and two randomized trials, indicating low confidence in the evidence for IVC filter efficacy. A similar conclusion of insufficient evidence to support IVC filter effectiveness was also reported from the National Institutes for Health and Care Excellence (NICE) review in 2020 [19].
The American College of Chest Physicians (ACCP) 2016 guidelines recommended the use of an IVC filter in patients with acute proximal DVT but in whom anticoagulants are contraindicated, such as those with active uncontrollable bleeding [20]. It is also considered reasonable that IVC filters be used for those thromboembolic patients in whom anticoagulation is perceived to have failed [21]. However, ACCP advises against the initial use of an IVC filter in addition to anticoagulants in patients with acute DVT of the leg [20]. This is primarily due to the efficacy and safety concerns regarding IVC filters. A similar recommendation was also advocated by the ASH guidelines [18]. In our opinion, the application of filter devices in clinical thrombotic conditions without approved indications, such as prophylactic use in patients without a history of PE, should be strongly discouraged. Moreover, a low retrieval rate after the placement of retrievable types of filters has further aggravated real-world adverse event-related conditions [22].
Various significant complications related to indwelling IVC filters have been noted [23], including thrombus formation related to the filter. The incidence of permanent filter-associated IVCT is approximately 13% after 8 years of follow-up [17]. Filter-related thromboembolism is known to be a complicated process and may be influenced by various filter types and designs, patient-specific underlying conditions, such as pregnancy or malignancy, and the intrinsic thrombogenicity of the device. A filter thrombus can be formed from entrapped emboli within the filter. Besides, the filter could induce thrombus formation, as it is a foreign body. A thrombus could also be formed by the extension of DVT to the veins of the lower extremities and iliac veins. Therefore, IVC filters should be judiciously used and retrieved whenever possible.
The goals of treating IVCT include reducing the risk of PE, decreasing chronic complications such as post-thrombotic syndrome, and decreasing venous insufficiency and the related symptoms. The management of IVCT consists of in-time administration of anticoagulants, if not contraindicated. Catheter-directed thrombolysis or thrombectomy may have rapid direct thrombolytic advantages [24], while percutaneous transluminal angioplasty with a stent may also be a reasonable choice [25]. The advantage of the investigational clot-removal strategy is to reduce post-thrombotic syndrome, although it is dependent on the physician’s experience.