In the last decade, PAE gained ground as an alternative minimally invasive procedure for LUTS / BPH, much based on its favorable safety profile, and the possibility of being performed on an outpatient basis (McWilliams et al, 2019; Wang et al, 2016; Uflacker et al, 2016; Malling et al, 2019; Feng et al, 2017; Pyo & Cho, 2017; Shim et al, 2017). NTE, however, remains a primary source of concern, leading to the investigation of novel protective technologies.
The reflux-control mechanism of the SeQure® microcatheter involves the discharge of filtered contrast solution through a small side fenestrate, creating a fluid barrier that avoids the reflux of microspheres, which are delivered by the distal-end hole of the device; thus, the microcatheter utilizes fluid dynamics to minimize the risk of NTE (Rizzitelli et al, 2021). In that sense, reflux of contrast solution is expected and seen routinely during embolization using this microcatheter, while the risk of embolic particle reflux is mitigated.
In 2021, a pre-clinical study (Rizzitelli et al, 2021) compared the outcomes of embolization using the SeQure® versus a standard end-hole microcatheter in 14 domestic pigs (28 kidneys). In this investigation, an automated injection protocol was used to ensure equivalent parameters. The embolization outcomes were assessed by angiography, gross pathology, and CT scans of the extracted kidneys. Although contrast reflux was visible in all cases during embolization, CT scans demonstrated more frequently areas of NTE of radiopaque microspheres in the standard microcatheter group in a qualitative analysis performed by 5 blinded interventional radiologists (least-square means of 3.8 vs. 3.2, P = 0.01). Similarly, in our study, all non-target branches were observed to be patent after embolization (Fig. 2).
In the present cohort, a strict clinical and radiological follow-up protocol including MRI showed that no clinical or subclinical NTE was observed, with a normal aspect of the periprostatic structures in all patients. Noteworthy that the microcatheter used potentially protects against microspheres reflux to non-target arterial branches; however, high-flow anastomosis to relevant structures should still be coiled to protect against NTE whenever present.
The grade III complication observed (ball-valve effect) occurred in a patient with a large prostate (130 cm3), and a 26 mm intraprostatic protrusion (grade III IPP) caused by a large, asymmetric medium lobe (Fig. 1). In fact, patients with a large medium lobe seem to be more frequently prone to complications after PAE. Meira et al. (Meira et al, 2021) recently reported the efficacy and safety of PAE in patients with different IPP grades, showing a higher overall incidence of complications in grade III IPP when compared with grade II (62.5% vs. 23.4% P ≤ 0.01). Also, all major complications observed in the cohort occurred in grade III IPP patients (3/32, 9.4%), which included ball-valve effect, hematuria needing cystoscopic management, and persistent urinary tract infection.
Using the 2.4-F reflux control microcatheter, bilateral embolization was possible in all 10 patients (100%), while deeper, intraprostatic navigation into the prostatic branches (PErFecTED technique) was possible in 24/25 prostatic branches (96.0%). Also, even in the type I PAs (7/25, 28%), which are considered as of harder catheterization (de Assis et al, 2015), no additional difficulty related to the material was observed. In one patient (10.0%), occlusion of the microcatheter was observed during the embolization of the first prostatic side with 300-500 μm Embospheres, and microcatheter exchange was necessary to resume PAE. After removing the microcatheter, occlusion of its distal end by impacted particles was observed, as well as exteriorization of embolic material through the damaged side holes during saline injection. Although we did not modify the dilution protocol after this episode, no other similar event was observed. It is possible that using a more diluted microsphere solution could help reduce the incidence of microcatheter occlusion and subsequent damage of the reflux control mechanism.
Regarding the efficacy outcomes, the improvements in IPSS and QoL scores and the objective endpoints such as Qmax, prostatic volume, and PSA levels were similar to those previously described in multiple single-center series and metanalyses (Wang et al, 2016; Uflacker et al, 2016; Malling et al, 2019; Feng et al, 2017; Pyo and Cho 2017; Shim et al, 2017; Carnevale et al, 2020b; Bagla et al, 2014) and lasted during the 12-month follow-up (Table 3). In 2019, a clinical trial comparing the outcomes of PAE using conventional (cPAE) versus balloon-occlusion microcatheter (bPAE) showed no difference in the efficacy outcomes between groups (Bilhim et al, 2019). Although coiling was employed as a protective measure in both arms (8.7% in the bPAE group and 14.0% in the cPAE group, P = 0.51), NTE resulting in penile lesions (n = 3, 7.0%) and rectal bleeding (n = 2, 4.7%) occurred only in the cPAE group. Similarly, we did not observe any clinical or subclinical NTE event.
Limitations of the present investigation include its small sample size, leading to higher variability of the results and possible bias. Also, it does not allow a definitive conclusion about the extent of the protection against NTE. Even so, it was possible to obtain statistical significance for all the intended endpoints using non-parametric tests. Also, the findings obtained were exclusively compared to historical data, in which populations are not necessarily similar regarding baseline aspects such as prostatic volume, arterial anatomy, and technique utilized, among others. Larger prospective trials would be more suitable to address the efficacy of PAE using the reflux-control microcatheter. Finally, no long-term data was obtained, although the short- and medium-term results presented were considered enough to attest to the feasibility of the method, even using a 2.4-F microcatheter, which is often considered too large for PAE.
In conclusion, this initial experience suggests that PAE using the reflux control microcatheter is effective and safe for the treatment of LUTS / BPH. No NTE was observed during follow-up.