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A small pilot study suggests that in certain men with erectile dysfunction who do not respond to standard drugs like Viagra and Cialis, stenting of lesions in the pelvic arteries can safely restore penile blood flow and significantly improve erections in about two-thirds of them.

The findings, from a first-in-man safety and feasibility trial marking interventionalists’ first foray into this territory, were presented by Jason H. Rogers, MD, of the University of California Davis Medical Center (Sacramento, CA), October 19, 2011, at VIVA (Vascular InterVentional Advances) 11 in Las Vegas, NV. 

In the ZEN trial, 30 men with erectile dysfunction and a suboptimal response to phosphodiesterase type 5 (PDE5) inhibitor therapy were implanted with zotarolimus-eluting peripheral stents (Medtronic; Minneapolis, MN) at 16 centers.

No Major Adverse Events

At 30 days, no patient had experienced the primary safety endpoint of a major adverse event, defined as device- and/or procedure-related death; perineal gangrene or necrosis; or perineal, penile, or anal surgery including TLR, TVR, or an arterial embolization procedure.

In the intention-to-treat analysis, more than half of the subjects (59%) met the primary feasibility endpoint of at least a 4-point improvement in the erectile function domain of the gold standard International Index of Erectile Function (IIEF) questionnaire at 3 months. In the per-protocol analysis (n = 22), 68.2% reported such improvement. This increment has been shown in multiple studies to correlate with clinical improvement in erectile function. The average 3-month increase in the overall IIEF score was 12.5 points. Moreover, the Sexual Encounter Profile—a measure of the frequency of successful intercourse—increased 18.2% over 30 days and 38.1% over 3 months.

Providing objective evidence of improved penile blood flow post procedure, duplex ultrasound showed that the peak systolic velocity in the cavernosal arteries increased by a mean of 16.5 cm/sec in the first 30 days. 

Data from 6-month angiographic and duplex ultrasound are not yet available. Clinical follow-up will extend to 5 years. 

Who Will Benefit?

“This is an entirely novel procedure, and we’re basically writing the book as we go,” Dr. Rogers told TCTMD in a telephone interview. “A big challenge for the future will be screening and identifying appropriate patients.”

Inclusion and exclusion criteria for this pilot study were quite strict, Dr. Rogers said, but he described how the huge population of men with erectile dysfunction—an estimated 30 million in the United States—would be winnowed to stenting candidates.

Because erectile dysfunction has a complex etiology, patients first need careful evaluation by a urologist or other physician who is knowledgeable about erectile dysfunction to rule out causes such as medication use, chronic disease, or psychological problems, he said.

“After that, what we’re looking for is the subset of patients who have atherosclerotic narrowing in the main vessels that supply the penis, the internal pudendal arteries, and do not have venous leak [which can deflate an erection],” Dr. Rogers said. Only after patients have been screened with duplex ultrasound and found to have inadequate penile blood flow do they receive angioplasty, which ultimately determines whether they are suitable for stenting, he explained.

In a telephone interview with TCTMD, Christopher J. White, MD, of the Ochsner Heart and Vascular Institute (New Orleans, LA), who performs the procedure, said he has no doubts about its ability to improve blood flow and erectile function.

Arguments For and Against

“The real question is: Of all the men who have ED, how many actually are candidates for this procedure?” Dr. White said. “The jury is still out on that. Some think the number is significant, and others—particularly the urologists I’ve spoken to—pooh-pooh the idea.”

Part of the skepticism stems from the bilateral circulation in the pelvis. Some believe that in order for blood flow to the penis to be significantly impeded, both internal pudendal arteries must be blocked, Dr. White reported. But Dr Rogers pointed out that about half of the men in the study received unilateral stenting (in many the contralateral artery had less than 50% stenosis), yet they still benefited from the procedure. Unfortunately, the small numbers of patients in the unilateral and bilateral groups precluded looking for a differential effect, he added.

Another factor that might diminish the pool of potential candidates, Dr. White said, is that a considerable proportion of men with ED are diabetic and so tend to have diffuse vascular disease that is not amenable to stenting. But Dr. Rogers countered that experience with coronary arteries shows that even diabetics develop focal lesions that require intervention. He agreed, however, that the effectiveness and longevity of pelvic stenting in this population remains to be determined. 

New Territory Means a Steep Learning Curve

Drs. Rogers and White agreed that the new procedure entails a steep learning curve. The vascular territory of the pelvis with its multiple branches is “completely foreign to the average cardiologist, so a significant amount of education needs to take place,” Dr. White said.

Dr. Rogers concurred, noting that the next important steps are to characterize the pelvic anatomy and its variants, understand the patterns of pelvic vascular disease in men with and without erectile dysfunction, and establish an angiographic protocol for reliably imaging the pelvic vessels—all goals of the ongoing IMPASSE (Incidence of Male Pudendal Artery Stenosis in Suboptimal Erections) study. 

Dr. White said that in his experience, interest in the procedure among interventionalists tends to depend on how they see the potential frequency of cases. “There is some healthy skepticism about the prevalence [of relevant pelvic vascular disease],” he commented. 

Not Ready for Prime Time 

Dr. Rogers, on the other hand, reported nearly universal fascination with the procedure among interventionalists. But he acknowledged a mismatch between enthusiasm and understanding. “This procedure isn’t ready for prime time,” he cautioned. “We need to do more research. We don’t want anybody to come away from these data thinking that this is a widely applicable therapy for patients with ED.” 

Dr. White likewise called for a measured approach. “It’s important for the field to remain very grounded and very objective. It’s too easy to get caught up in enthusiasm [based on] anecdotal benefit,” he observed. Eventually, a randomized controlled trial of stenting vs. medical therapy will be required, he said, adding that it is crucial that it be blinded to avoid the potential psychological impact of receiving a procedure. 

Meanwhile, Dr. Rogers stressed that stenting should be viewed as an adjunct to existing therapies, not a cure. The underlying disease will persist, requiring a healthy lifestyle and perhaps medical therapy. Drugs like Viagra may still be needed, he added, but at least with greater penile blood flow, the response may more satisfactory.

Study Details

The average age was 60.1 ± 7.7 years. Baseline characteristics included a history of MI in 20%, stroke in 13.3%, unstable angina in 6.7%, and tobacco use in 40.0%. Dual antiplatelet therapy was recommended for at least 6 months. 

Coauthors of the study include Krishna Rocha-Singh, MD, of the Prairie Vascular Institute (Springfield, IL), and Irwin Goldstein, MD, of San Diego Sexual Medicine (San Diego, CA).

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