Micro-CT–compatible Technique for Measuring Self-expanding Stent Forces

Radial Force: An Underestimated Parameter in Oversizing Transcatheter Aortic Valve Replacement Prostheses: In Vitro Analysis with Five Commercialized Valves

The goal is to inform in depth on transcatheter aortic valve replacement (TAVR) prosthesis mechanical behavior, depending on frame type, design, and size, and how it crucially impacts the oversizing issue in clinical use, and ultimately the procedure outcome. Transcatheter aortic valve replacement is an established therapy for high-risk patients suffering from aortic stenosis, and the indication for TAVR is progressively expanding to intermediate-risk patients. Choosing the optimal oversizing degree is crucial to safely anchor the TAVR valve-which involves limiting the risks for embolism, aortic regurgitation, conductance disturbance, or annulus rupture-and to increase the valve prosthesis performance. The radial force (RF) profiles of five TAVR prostheses were measured in vitro: the CoreValve 23 and 26 (Medtronic, Minneapolis, MN), the Acurate neo S (Symetis, Écublens, Vaud, Switzerland), and the SAPIEN XT 23 and 26 (Edwards Lifesciences, Irvine, CA). Measurements were run with the RX Machine equipment (Machine Solutions Inc., Flagstaff, AZ), which is used in ISO standard tests for intravascular stents. Test protocols were adapted for TAVR prostheses. With the prostheses RF profiles' results, mechanical behavior differences could be described and discussed in terms of oversizing strategy and clinical impact for all five valves. Besides, crossing the prostheses' RF profiles with their recommended size windows made the assessment of borderline size cases possible and helped analyze the risks when accurate measurement of patient aortic annulus proves difficult. The prostheses' RF profiles bring new support in clinical decision-making for valve type and size in patients.

Role of Stent Selection in the Incidence of Persisting Hemodynamic Depression After Carotid Artery Stenting

Purpose: To investigate the possible role of stent selection and procedure-related vessel diameter changes in the development of persisting hemodynamic depression (PHD) and to demonstrate the effectiveness and safety of permanent pacemaker implantation in patients with refractory PHD. Methods: Data from 584 procedures performed in 542 patients (398 men; mean age 67.3 years) between 2008 and 2011 using Wallstent, Precise, and Xact stents in a nonrandomized fashion were analyzed retrospectively. Cardiovascular risk factors and lesion, stent, and balloon characteristics were collected, and the pre- and postprocedure diameters of the common carotid artery (CCA) and internal carotid artery were measured. PHD was defined as any episode of hypotension (systolic blood pressure <90 mm Hg) and/or bradycardia (heart rate <60/min) lasting >6 hours. Risk factors for PHD were sought using logistic regression analyses; the results are presented as the odds ratio (OR) and 95% confidence interval (CI). Results: The incidence of PHD was 37.0% (216/584). Refractory PHD was encountered in 9 patients; among these, 6 were successfully treated with pacemaker implantation. A history of prior ipsilateral carotid endarterectomy (OR 0.44, 95% CI 0.22 to 0.87, p=0.019) and the presence of a contralateral high-grade stenosis (OR 0.12, 95% CI 0.02 to 0.95, p=0.045) were independent protective factors, while calcification (OR 1.5, 95% CI 1.03 to 2.18, p=0.034), involvement of the carotid bulb (OR 2.56, 95% 1.62 to 4.03, p<0.001), and implantation of a nitinol stent (adjusted OR 1.62, 95% CI 1.12 to 2.34, p=0.011) were independent risk factors for developing PHD after carotid artery stenting. The ratio of the post-/preprocedure CCA diameter (p=0.002), the stent to CCA diameter ratio (p=0.009), and the presence of residual stenosis (p=0.009) were significantly higher in the PHD group. Conclusion: Stent selection and procedure-related changes in vessel diameter may have an influence on the development of PHD. Permanent pacemaker implantation is an effective treatment option in patients with refractory PHD.

Treatment of traumatic penile urethral stricture in a dog with a self-expanding, covered nitinol stent

CASE DESCRIPTION

An 8-month-old castrated male mixed-breed dog was evaluated because of hematuria, stranguria, and dysuria of approximately 2 weeks' duration that developed immediately following elective castration.

CLINICAL FINDINGS

Results of physical examination, ultrasonography, retrograde double-contrast cystourethrography, and urethroscopy were consistent with a traumatic urethral stricture immediately proximal to the os penis resulting in a partial obstruction of urine outflow. Results of ultrasonographic examination of abdominal organs were considered normal. Digital radiography revealed no evidence of calculi.

TREATMENT AND OUTCOME

Balloon dilation of the urethral stricture was performed and was followed by 2 bougienage procedures during the subsequent 2 weeks when clinical signs returned. The owners declined scrotal urethrostomy, and a self-expanding, covered nitinol stent was placed approximately 3 weeks after the initial evaluation, resulting in amelioration of clinical signs. Results of follow-up urethroscopy and contrast cystourethrography 1 year after stent placement revealed a statically positioned, patent urethral stent, although a small number of polypoid mucosal structures were identified distal to the stent and 1 small structure consistent with tissue ingrowth into the stent was identified.

CLINICAL RELEVANCE

Placement of a covered nitinol stent resulted in long-term resolution of clinical signs associated with traumatic stricture of the penile urethra in this young dog. Because the os penis in dogs limits radial expansion of the urethra, its presence may limit the use of stents in this location.