Author + information
- Received July 13, 2012
- Revision received August 13, 2012
- Accepted August 30, 2012
- Published online December 25, 2012.
- Jason H. Rogers, MD⁎,
- Irwin Goldstein, MD†,
- David E. Kandzari, MD‡,
- Tobias S. Köhler, MD, MPH§,
- Curtiss T. Stinis, MD∥,
- Paula J. Wagner, FNP, MSN¶,
- Jeffrey J. Popma, MD#,
- Michael R. Jaff, DO⁎⁎ and
- Krishna J. Rocha-Singh, MD††,⁎ ()
- ↵⁎Reprints requests and correspondence:
Dr. Krishna J. Rocha-Singh, Prairie Vascular Institute at St. John's Hospital, 619 East Mason Street, Springfield, Illinois 62701
Objectives This study sought to evaluate the safety and feasibility of zotarolimus-eluting stent implantation in focal atherosclerotic lesions of the internal pudendal arteries among men with erectile dysfunction (ED) and a suboptimal response to phosphodiesterase-5 inhibitors.
Background ED, a common condition, is often mediated by atherosclerosis. Current treatment options are limited.
Methods Male subjects with atherosclerotic ED and a suboptimal response to phosphodiesterase-5 inhibitors were enrolled in this prospective, multicenter, single-armed safety and feasibility trial. A novel combination of clinical, duplex ultrasound, and invasive angiographic factors were used to determine eligibility for stent therapy. The primary safety endpoint was any major adverse event 30 days after the procedure. The primary feasibility end point was improvement in the International Index of Erectile Function (Erectile Dysfunction Domain) score ≥4 points in ≥50% of subjects at 3 months. We report 6-month follow-up results, including duplex ultrasound and angiography.
Results Forty-five lesions were treated with stents in 30 subjects. Procedural success was 100% with no major adverse events through follow-up. The primary feasibility endpoint at 6 months was achieved by 59.3% of intention-to-treat subjects (95% confidence interval: 38.8% to 77.6%) and 69.6% of per-protocol subjects (95% confidence interval: 47.1% to 86.8%). Duplex ultrasound peak systolic velocity of the cavernosal arteries increased from baseline by 14.4 ± 10.7 cm/s at 30 days and 22.5 ± 23.7 cm/s at 6 months. Angiographic binary restenosis (≥50% lumen diameter stenosis) was reported in 11 (34.4%) of 32 lesions.
Conclusions Among patients with ED and limited response with pharmacologic therapy, percutaneous stent revascularization of the internal pudendal artery is feasible and is associated with clinically meaningful improvement in both subjective and objective measures of erectile function. (Safety and Feasibility of the Zotarolimus Stent in Treating Males With Erectile Dysfunction (ED) (ZEN); NCT01643200).
- erectile dysfunction diagnosis
- internal pudendal artery
- zotarolimus-eluting stent
Erectile dysfunction (ED) is defined as the recurrent inability to achieve and maintain an erection satisfactory for sexual intercourse (1). Successful treatment of ED has a strong impact on quality of life (2,3). More than 150 million men worldwide have ED, and 52% of men in the United States 40 to 70 years of age report some degree of ED (4,5). ED is managed by identifying and treating any reversible causes, followed by an oral phosphodiesterase-5 inhibitor (PDE5i) trial. However, up to 50% of men have a suboptimal response to PDE5i therapy, and because subsequent therapies tend to be more intrusive (such as penile injection therapy with vasodilators, vacuum pump therapy, or penile implants), there is a need for additional therapies (6). It is well known that ED and coronary artery disease share common vascular risk factors such as age, diabetes, hypertension, dyslipidemia, and tobacco use (7–9). These factors contribute to ED through consequent endothelial dysfunction, abnormal vasomotion, and atherosclerosis. The presence of ED significantly increases the risk of developing cardiovascular disease, and up to 70% of men with new-onset angina and angiographically documented coronary artery disease have a history of antecedent ED (10–13).
Restoring adequate arterial inflow in patients with penile arterial insufficiency can improve erectile function. Surgical revascularization has been used successfully in younger men after blunt perineal trauma or pelvic fracture (14). Older subjects can have obstructive atherosclerotic disease identified by angiography in the iliac, internal pudendal, and cavernosal arteries (15–19). Although endovascular revascularization with balloon angioplasty has resulted in at least short-term improvement of erectile function, there have been no prior reports on the feasibility of endovascular stents for ED (18).
We conducted the first-in-man ZEN (Zotarolimus-Eluting Peripheral Stent System for the Treatment of Erectile Dysfunction in Males with Suboptimal Response to PDE5 Inhibitors) trial examining the safety and feasibility of using a balloon-expandable peripheral drug-eluting stent (DES) to treat selected patients with atherosclerotic ED and unilateral or bilateral focal internal pudendal artery (IPA) stenoses.
Subjects were screened at 16 centers in the United States. The institutional review board approved the study at each site and informed consent was obtained from all subjects. A multidisciplinary team consisting of a urologist with expertise in sexual medicine and a vascular interventional specialist evaluated all subjects.
Subject enrollment and attrition is illustrated in Figure 1. Key inclusion criteria were: 1) men 18 years of age or older in an active sexual relationship with 1 partner ≥6 months; 2) suboptimal response to PDE5i therapy, as documented by a 4-week run-in phase; 3) reduced cavernosal arterial penile flow with duplex ultrasound (DUS) peak systolic velocity (PSV) of the right and left cavernosal arteries <30 cm/s; 4) cavernosal artery anteroposterior and transverse diameter at mid-shaft ≥0.3 mm; and 5) angiographic stenosis of one or both IPA with target vessel reference diameter(s) ≥2.25 mm and ≤4.20 mm by visual estimation and primary lesion length(s) ≤27 mm. Key exclusion criteria were: 1) any nonvascular cause of ED (i.e., prostatectomy, pelvic radiation, pelvic trauma, Peyronie's disease, hormonal, psychogenic, etc.); 2) untreated hypogonadism (serum total testosterone <300 ng/dl within 7 days before enrollment); 3) diabetes mellitus with glycosylated hemoglobin levels ≥8%; 4) chemotherapy in the prior 12 months or life expectancy of fewer than 12 months; 5) myocardial infarction, cardiovascular accident, life-threatening arrhythmia, or unstable angina requiring hospitalization within 3 months before enrollment, or any subject actively receiving nitrate therapy; 6) bleeding diathesis or known hypercoagulable state; 7) penile veno-occlusive dysfunction (venous leak) by DUS with right or left cavernosal artery end-diastolic velocity >5 cm/s; 8) serum creatinine levels >2.5 mg/dl; and 9) nontarget lesions of the common iliac artery, IIA, or common penile artery ≥70%.
International index for erectile function and the sexual encounter profile
The International Index for Erectile Function (IIEF) (20) and Sexual Encounter Profile (21) questionnaires have been validated in numerous previous clinical trials as useful instruments for measuring efficacy of ED interventions (22). Eligible subjects first were provided with a baseline IIEF questionnaire consisting of 15 questions divided into the following 5 domains: erectile function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction. We used the IIEF-6 domain score, which is a subset of 6 questions specific to erectile function (score range: 1 to 30). The IIEF-6 questionnaire has been shown to discriminate highly between men with and without ED with an optimal cutoff score ≤21 for establishing ED diagnosis (20). A baseline IIEF-6 score of >6 and ≤21 was required before proceeding to a 4-week run-in phase, during which time at least 4 attempts at intercourse were required while the patient was taking PDE5i.
After each attempt at intercourse, the subject completed the Sexual Encounter Profile diary. On completion of the 4-week run-in phase, subjects continued with the screening process if they responded “No” to question 3 (“Did your erection last long enough for you to have successful intercourse?”) at least 50% of the time. Subjects then took a second IIEF assessment to evaluate his response to the 4-week run-in on PDE5i treatment, and if the IIEF-6 domain score remained at >6 and ≤21, they qualified to undergo further screening.
Penile duplex ultrasonography
Penile DUS was performed following a standardized protocol with a pharmacologically induced erection via direct injection of intracavernosal alprostadil (10 to 40 μg). After visual or manual stimulation as required to achieve maximal erection, the subject's cavernosal artery diameters and PSV were assessed for eligibility. End diastolic velocities were assessed at peak erection. An insonation angle of >60 degrees was required, and the standardized protocol and all DUS studies were interpreted by a core laboratory (VasCore, Massachusetts General Hospital, Boston, Massachusetts). If subjects met ultrasound criteria, they then were scheduled for angiography with possible intervention.
Angiography was performed to define the anatomic features of all erectile-related arteries (Fig. 2). A pharmacologically induced partial erection was recommended and was obtained by injecting 10 to 40 μg of intracavernosal alprostadil. Anteroposterior projections were used for the distal aorta and common iliac arteries, contralateral projections for the internal iliac origins, ipsilateral cranial views for the IPA origins, and anteroposterior or ipsilateral straight oblique or caudal angulations were best for visualizing the body and distal IPA. Subjects could proceed with investigational stent therapy if the visual estimate demonstrated an IPA lesion length ≤27 mm and either: 1) unilateral stenosis ≥70% and ≤100% with contralateral vessel stenosis <50% (or stenosis ≥50% and ≤100% if contralateral vessel was 100% occluded); or 2) bilateral stenosis >50% and ≤100% in each vessel. The intent of these angiographic inclusion criteria was to include subjects with severe unilateral (in the presence of mild or occluded contralateral vessel disease) or moderate to severe bilateral IPA disease. Subjects were excluded if there was ≥70% stenosis of non-IPA erectile-related arteries.
Quantitative angiography (CMS, Leiden, the Netherlands) was performed by observers in an angiographic core laboratory (Beth Israel Deaconess Medical Center, Boston, Massachusetts) who were unaware of the clinical outcomes. The proximal and distal reference vessel diameter and the minimal lumen diameter were used to determine the percent diameter stenosis before and after the procedures and at the 6-month follow-up. Binary restenosis was defined as ≥50% diameter stenosis on follow-up angiography. Acute gain was defined as the increase in the minimal lumen diameter from the baseline to the post-procedure angiogram; late lumen loss was defined as the loss in minimal lumen diameter from the post-procedural to the follow-up angiogram. Stent integrity was defined as the absence of stent fracture or deformation during the follow-up period.
Stent device and interventional procedure
The Resolute Zotarolimus-Eluting Stent System (Medtronic, Santa Rosa, California) is composed of a cobalt-chromium alloy platform coated with a biocompatible tripolymer (Biolinx) containing the antiproliferative agent zotarolimus at a concentration of 1.6 μg/mm2. Zotarolimus, a tetrazole-containing macrocyclic immunosuppressant, is eluted over 180 days. Because the IPA has a smaller average diameter (approximately 2.6 mm in this study), a DES was chosen over bare-metal stent in hopes of minimizing restenosis rates. Available stent sizes range from 2.25 to 4.0 mm in diameter and 8 to 30 mm in length.
On confirmation of angiographic eligibility, subjects received heparin to achieve an activated clotting time ≥250 s before and during stent placement. All subjects received 325 mg aspirin within 24 h of the procedure and daily thereafter for at least 6 months. A loading dose of clopidogrel ≥300 mg (or ticlopidine if allergic) was given periprocedurally, and clopidogrel 75 mg daily was required for 6 months. Use of any PDE5i within 36 h of the procedure was prohibited, and PDE5i use was resumed in follow-up at investigator discretion as clinically required. In general, single femoral vascular access was performed to treat both the ipsilateral and contralateral IPA. A guiding catheter or sheath was brought into or near the IPA origin, and the lesion was crossed with a 0.014-inch guidewire and was treated using standard interventional techniques. Pre-dilatation with a balloon catheter less than or equal to the reference diameter of the artery was performed, and direct stenting was not allowed. This was to provide adequate lesion assessment and preparation before stent placement. Target lesions were treated with a single stent whenever possible, but up to 2 stents could be placed in an overlapping manner to cover longer lesions up to 27 mm or multiple lesions (provided the primary lesion met angiographic eligibility) or to cover any stent-edge dissections. The study protocol limited the use of stents to 2 per IPA and to no more than 4 total per subject. Post-dilation was not required and was performed at operator discretion. The procedure was considered a failure if the stent could not cross the target lesion after adequate pre-dilation.
The primary safety endpoints were major adverse events at 30 days defined as device- or procedure-related death, or both; occurrence of perineal gangrene or necrosis (glans penis, penile shaft, scrotal or anal); or the need for subsequent perineal, penile, or anal surgery (including target lesion or vessel revascularization or arterial embolization procedures). The primary feasibility endpoint was obtained at 3 months and was defined as improvement in erectile function from pre-procedure of the IIEF-6 score by ≥4 points in ≥50% of subjects. A change of ≥4 points in the IIEF-6 score has been shown to be the minimal clinically important difference for assessing a meaningful change in erectile function and has been validated across a broad spectrum of ED therapies (23). An improvement in at least 50% of subjects was chosen empirically as a reasonable goal for therapy.
Secondary endpoints included the major adverse event rate at 3 and 6 months; changes in sexual function from pre-procedure as assessed by the IIEF at 30 days and 6 months; mean PSV as assessed by DUS in the right and left cavernosal arteries at the mid-shaft during pharmacologically induced erection within 30 days and 6 months, and 12 months post-procedure; restenosis and stent integrity as assessed by angiography at 6 months. Claudication by vascular territory was assessed by change in Rutherford class. The Harvard Clinical Research Institute (Boston, Massachusetts) coordinated an independent data monitoring committee, which reviewed any adverse events reported during the conduct of the study. All subjects will be followed up yearly for 5 years.
Descriptive statistics were performed, including frequencies and mean ± SD. To test for predictors of binary restenosis at the 6-month follow-up, a univariate analysis was performed on demographic variables, medical history and risk factors, procedure and lesion characteristics, and pre-procedure IIEF total score. A p value < 0.05 was considered statistically significant. SAS software version 9.1 (SAS Institute, Cary, North Carolina) was used for all analyses.
A total of 30 subjects had 45 stents placed. The enrollment flowchart (Fig. 1) illustrates subject screening and enrollment details. The most common DUS exclusions were adequate arterial inflow and venous leak. Of 89 subjects who underwent angiography, approximately one-third were found to have insufficient disease (n = 29, 32.5%), and one third had excessive disease (n = 30, 33.7%).
Baseline demographics are reported in Table 1. The mean age was 60.1 years (range: 43 to 77 years). Although many subjects had known cardiovascular risk factors, most subjects had no history of ischemic heart disease. These distributions may reflect that patients were identified from both cardiovascular and urologic practice settings.
Procedure and lesion characteristics
Mean hospital stay was 0.5 ± 0.5 days, and mean procedure duration was 102.5 ± 34.9 min. There were no deaths during the study. Angiographic lesion characteristics are described in Table 2. The mean lesion length was 17.6 ± 9.9 mm (range: 2.47 to 45.88 mm), 33 of 45 lesions (73.3%) were eccentric, and no lesion was ulcerated or thrombotic. Mild or no calcification was seen in 44 lesions (97.8%), moderate calcification was seen in 1 lesion (2.2%), and no lesions were severely calcified.
Procedural success was 100%. Target lesions were most prevalent in the distal IPA (24 lesions, 53.3%), followed by 6 lesions in the ostial IPA (13.3%), 5 proximal IPA lesions (11.1%), and 4 lesions in the mid-IPA (8.9%). Post-stent balloon dilatation was performed in 50% of lesions, with a mean nominal balloon diameter of 2.7 ± 0.4 and a mean maximal stent balloon pressure of 15.0 ± 3.7 atmospheres. A case example is shown in Figure 3.
Primary and secondary endpoints
The primary safety endpoint at 30 days was met in all subjects and there were no subsequent safety events during the 6 months of follow-up. In the intention-to-treat analysis, the primary feasibility endpoint (IIEF improvement of ≥4 points) at 3 months was achieved in 59.3% (95% confidence interval [CI]: 38.8% to 77.6%) of 27 reported subjects at 3 months and was unchanged at 6 months. In the per-protocol analysis at 3 months, 68.2% (95% CI: 45.1% to 86.1%) of subjects were observed to have IIEF improvement of ≥4 points, and at 6 months, 69.6% (95% CI: 47.1% to 86.8%) of per-protocol subjects showed IIEF improvement (Table 3).
The per-protocol analysis excluded 5 subjects who were observed by the core laboratory to have lesions in pelvic arteries other than the IPA (2 obturator arteries, 2 middle rectal arteries, and 1 inferior gluteal artery), resulting in a per-protocol cohort size of 25 subjects. Given the first-in-man nature of this protocol and the variability of pelvic vascular anatomic features, inadvertent stenting of a nontarget vessel was not unexpected. However, there were no safety issues identified with stenting non-IPA vessels seen through 6 months of follow-up. Two subjects in the per-protocol analysis were unavailable for follow-up at 3 months, but both subjects returned for follow-up at 6 months. One subject declined follow-up at 6 months.
Secondary endpoints are shown in Table 3. There were no stent fractures seen in follow-up.
The total change in IIEF domain score from pre-procedure to 6 months was 12.5 (95% CI: 6.1 to 19.0). The incremental change of IIEF and PSV over time is illustrated in Figure 4. The mean angiographic percent stenosis pre-procedure (number of lesions: 45), post-procedure (number of lesions: 45), and at 6 months (number of lesions: 32) was 63.3%, 23.3%, and 41.4%, respectively. The mean change in PSV from baseline was 14.4 ± 10.7 cm/s at 30 days and 22.5 ± 23.7 cm/s at 6 months.
Binary restenosis was seen in 11 (34.4%) of 32 lesions. Univariate analysis of baseline procedural and demographic variables did not identify any statistically significant predictors of binary restenosis at 6 months. At baseline, 4 (13.3%) of 30 subjects had Rutherford classification of ≥1. At both the 3-month and 6-month follow-up, 3 (10%) of 30 subjects had a Rutherford classification of ≥1. The percentage of subjects who were compliant with follow-up visits at 30 days (n = 30), 3 months (n = 30), and 6 months (n = 28) was 73.3%, 80.0%, and 82.1%, respectively.
The ZEN trial is a first-in-man investigation assessing the safety and feasibility of stenting atherosclerotic IPA lesions in highly selected subjects. Stenting of the IPA was found to be technically feasible and safe and was performed with high procedural success rates. Many subjects (but not all) reported subjective improvement in erectile function after these procedures, and there were concomitant increases in penile flow as determined by DUS. Angiographic follow-up demonstrated no stent fractures and reasonable binary patency considering the first-in-man use of a DES in a new vascular bed.
In addition to intact neurovascular, hormonal, and structural mechanisms, initiation and maintenance of erection depends not only on adequate arterial inflow but also on veno-occlusive function. That is, blood should enter the cavernosal bodies, which then enlarge and compress the emissary veins, preventing venous leakage during erection. If venous leak is present, adequate erection may not occur even in the presence of adequate arterial inflow. During ultrasound screening for the ZEN trial, venous leak frequently was encountered, and those subjects were not enrolled.
The importance of adequate arterial inflow to the penis for initiation and maintenance of erection is well known and was first described in 1923 by the French surgeon René Leriche, who observed that aortoiliac occlusion caused impotence because of failure of perfusion of the corporal bodies (24). The vascular inflow to the penis necessary for adequate erectile function requires patency of erectile-related arteries, which are shown in Figure 2 (18). The IPA is the longest named segment of arterial inflow to the penis, and the length is approximately 15 cm from its origin to the base of the penis. It travels in a neurovascular bundle along with the internal pudendal nerve, initially in an inferior and posterior direction inside the pelvis, then exits the pelvis through the inferior aspect of the greater sciatic foramen, finally entering the pudendal (Alcock's) canal, where it travels anteriorly and medially toward the base of the penis. The IPA experiences a low-flow state most of the time, interspersed with high-flow conditions during erection. As such, the IPA may have unique physiologic properties that allow it to remodel more efficiently and thus be a more rational target for vascular intervention (25,26). The distal IPA becomes the common penile artery, which gives rise to the 2 paired arteries, the cavernosal (deep penile) and dorsal penile arteries, which are important for tumescence.
Surgical revascularization of penile arterial inflow usually is reserved for younger patients with a history of trauma and is performed only in specialized centers (27). Endovascular revascularization has been described in case reports, mostly in the 1980s, which used percutaneous transluminal angioplasty without stenting of erectile-related arteries in younger to middle-aged men with ED (28–33). In these reports, there was no standardized pre-procedure evaluation of ED cause, and clinical follow-up was short. This literature has been reviewed in detail elsewhere (18). More recently, the PANPI (Pelvic Angiography in Non-Responders to Phosphodiesterase-5 Inhibitors) study was the first study to describe the angiographic characteristics of pelvic arterial disease in patients with ED who were nonresponsive to PDE5i treatment and had suspected coronary artery disease (17). In this report, the IPAs were found to have atherosclerotic narrowings similar to those in the coronary arteries, and the average IPA vessel diameter was just slightly less than the average coronary artery diameter.
Although the ZEN trial demonstrated safe and feasible stenting of the IPA in selected patients with arterial insufficiency, there was a significant learning curve to the procedure, and the identification of responders to stent therapy remains a subject of investigation. Most patients screened for this trial did not qualify and the main reasons for exclusion were: 1) excessive or insufficient angiographic disease; 2) lack of arterial insufficiency by duplex; or 3) venous leak. The data from the ZEN trial are not sufficient to warrant widespread adoption of this new technique. Many questions remain related to patient selection, the vascular biological features of the IPA, the hemodynamic and functional consequences of atherosclerotic IPA lesions, and the longer-term efficacy and durability of stent therapy. We observed a much higher binary restenosis rate at 6 months (34%) with the Resolute-DES platform than has been observed in the coronary circulation (9.2% binary in-stent restenosis in the Resolute US Trial) (34). This difference highlights the unknowns in applying DES to the pelvic vasculature. The mechanism by which clinical improvement in erectile function persisted at 6 months despite angiographic binary restenosis in one third of subjects remains unknown. No relationship between restenosis and IIEF-6 scores was seen during follow-up, although the small number of patients precludes any formal statistical analysis. This phenomenon is not well understood, but may reflect interim distal vascular remodeling during a period of increased penile flow (before restenosis). Psychological benefits of the procedure also may play a role, although these would be expected to diminish over time. Further, because of variability in pelvic anatomic features, the IPA was not always readily identifiable, and 5 subjects had non-IPA vessels stented with no adverse consequences. It is possible that computed tomography angiography before performing invasive angiography could be useful to delineate pelvic vascular anatomic features (35–37). Approximately one third of subjects had excessive atherosclerotic or diffuse disease by angiography that precluded stent therapy. The efficacy of angioplasty alone or drug-eluting balloons warrants further study in this subgroup. Another one third of subjects undergoing screening angiography were found to have minimal or no angiographic atherosclerotic disease. These individuals may have vascular remodeling of their IPA that may confer increased vascular inflow resistance during high-flow states (38).
These data represent a first-in-man experience and reflect intrinsic variability in case selection and stent deployment technique. There is no control arm, although the minimal clinically important difference has been well validated as a measure of clinical efficacy for ED therapies. There is also incomplete follow-up, and some DUS examinations were not interpretable formally by the core laboratory because of the early learning curve by the sites related to the required Doppler angle of insonation.
Drug-eluting stent therapy for atherosclerotic ED in selected patients who have not responded to PDE5i therapy is safe and feasible, can improve arterial inflow, and can result in improvement of erectile function. Defining appropriate patient selection undoubtedly will be crucial to the success of any endovascular approach. Patients with longstanding ED, veno-occlusive disease, or severe diffuse arterial disease likely will not be candidates for current endovascular therapies. Randomized trials are needed to assess efficacy of this new technique against the best existing therapies. Finally, the true prevalence of stenoses amenable to percutaneous therapy in patients with ED currently is not known, and further investigations are needed.
The authors appreciate the help of the following individuals from Medtronic: Mark Dolan, Jenifer Foss, Kim O'Connell, and Zachary Woodson. They acknowledge Matt Groesbeck for assistance in manuscript preparation, and illustrator Laura Maaske (www.medimagery.com).
The ZEN trial was funded by Medtronic Cardiovascular, Santa Rosa, California. Dr. Rogers is a consultant for Medtronic. Dr. Goldstein is a consultant for, and receives honoraria from Medtronic. Dr. Kandzari receives research/grant support and consulting honoraria from Medtronic. Dr. Köhler receives research/grant funding from American Medical Systems, Medtronic, Abbott, and Hollister; is a consultant for Medtronic, Actient, American Medical Systems, Coloplast; and is a speaker for Auxilium and Allergan. Dr. Stinis is a consultant for Medtronic, Abbott Vascular, Edwards Lifesciences, and Cook Medical. Dr. Popma is a consultant for and receives research grants from Medtronic. Dr. Jaff is a consultant for Medtronic. Dr. Rocha-Singh is a consultant of Medtronic. Ms. Wagner has reported that she has no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- confidence interval
- drug-eluting stent(s)
- duplex ultrasound
- erectile dysfunction
- internal iliac artery
- International Index of Erectile Function
- internal pudendal artery
- phosphodiesterase-5 inhibitor
- peak systolic velocity
- Received July 13, 2012.
- Revision received August 13, 2012.
- Accepted August 30, 2012.
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