Shelley Wood

November 05, 2013

SAN FRANCISCO, CA — A small Taiwanese study is picking up where the ZEN trial left off, testing balloon angioplasty (but not stents) in the penile arteries as a treatment for erectile dysfunction (ED).

Presenting the results of the PERFECT-1 trial at TCT 2013 last week, Dr Tzung-Dau Wang (National Taiwan University Hospital, Taipei City) reported that penile-artery angioplasty is a safe and effective treatment for men with ED, producing "clinically durable improvement" in 60% of treated patients.

As previously reported by heartwire , the ZEN study was an early effort to treat erectile dysfunction using drug-eluting stents (DES) in the internal pudendal arteries. Momentum for studying DES in this setting slumped, however, after participating sites failed to identify enough men believed to be suited to the intervention—namely, men with focal atherosclerotic narrowing of one or both internal pudendal arteries. A larger trial known as IMPASSE was subsequently terminated by the sponsor.

Dr Jason Rogers (University of California, Davis), the principal investigator for the ZEN trial, noted that there are other pockets of investigation still exploring DES in erectile dysfunction, but little cross-talk between groups.

Seeking the Perfect Solution

In Taiwan, Wang and colleagues have revived the idea, taking a slightly different approach. For starters, Wang explained to heartwire , refinements to existing technology have made the concept of penile-artery angioplasty worth revisiting. For one, balloon catheter sizes have gotten smaller, while the advent of CT angiography has made accurate imaging of the penile arteries that much more feasible.

Dr Tzung-Dau Wang

Indeed, in a separate poster session also presented at TCT, Wang reported results for 80 patients with erectile dysfunction in whom multidetector CT angiography identified 157 obstructive segmental lesions. The bulk of these (45%) were in the penile-artery segments, followed by the internal pudendal-artery segments. Importantly, almost one-third of the patients' lesions were limited to the penile arteries alone, with no other artery involvement. By contrast, only 13% of men had disease confined solely to the internal pudendal arteries.

That's important, Wang explained, because the ZEN trial was focused on the internal pudendal arteries—the idea being that restoring proximal blood flow was key to restoring erectile function. "In our study, almost half of the lesions were in the penile artery, and you have to reopen these lesions to improve function. You can't adopt the approach used in the coronaries and only open the proximal obstructions."

Commenting on Wang et al's study for heartwire , Rogers notes that ZEN investigators "also found that atherosclerotic disease often extends from the distal [internal pudendal artery] IPA into the common penile artery, and we were able to stent some of these lesions as long as the diameter of the common penile artery was large enough to accept a stent." In ZEN, he added, 53.3% of the lesions were in the "distal IPA," which often extended into the common penile artery.

For PERFECT-1, Wang focused on the 16 patients with isolated penile-artery stenosis, a number trimmed down to 12 after four patients failed on the basis of angiographic criteria. Technical success with balloon angioplasty in the remaining 12 was 100% in the 14 vessels treated. Percent lesion stenosis improved from a mean of 80% preprocedure to 12% immediately postintervention. At one month and three months, clinical success (defined as change in International Index of Erectile Function [IIEF-5] score of four or more points) was seen in a total of 83% and 58% of patients, respectively. No patients experienced worsening ED over the study follow-up, and no adverse events occurred.

"As far as I know, this is the first report of using balloon angioplasty for the penile artery, and that's probably because of the advances we've seen with the instruments we use," Wang commented. "They are getting smaller and smaller. We now have a 1.0-mm balloon we can use, and that's quite convenient [in this setting]."

Next Up: Drug-Eluting Balloons in the Penis?

Wang acknowledges the limitations to his study, including the small numbers, the lack of a control group, no objective assessment of penile blood flow using Doppler ultrasound or fractional flow reserve (FFR), etc. He also admitted there are clear signs of waning clinical efficacy over time.

"There are still a lot of barriers to cross, because we do see some restenosis, and even though our initial success at three months is pretty good, we did have some patients who did not respond."

His hope is that penile-artery stenosis may be a new frontier, not for DES, which may be too large to be useful in the penile arteries, but for drug-eluting balloons, which currently do not come in small enough sizes to be tested in this setting.

"Maybe if you write about it, that will happen," he said.

Hurdles Ahead

Commenting on PERFECT 1 for heartwire , Dr David Kandzari (Piedmont Heart Institute, Atlanta, GA) said that while he was "pleased to see someone revisiting" the question of catheter interventions for erectile dysfunction, he predicts angioplasty will face many of the same hurdles faced by ZEN and IMPASSE.

Key among these is the fact that erectile dysfunction has underlying causes "aside from or in addition to sclerotic disease." These include low testosterone, psychological issues, and most important, venous leak. Even if the underlying arterial lesions are corrected, prior trauma to the vasculature or even fibrosis as part of natural aging can leave the veins no longer able to collapse during an erection, causing any increased blood flow to the penis to "leak" back out, he explained.

Angioplasty, in other words, may improve arterial flow without improving ED symptoms.

Rogers, for his part, pointed to PERFECT-1's relatively short-term follow-up and lack of comprehensive screening to rule out other common causes of ED.

"Durability of [percutaneous transluminal angioplasty] PTA in these vessels will be a concern; even with DES in the ZEN trial, the angiographic restenosis rate at six months was 34.4%," he noted. "Erectile dysfunction is a complicated disease state that is between the ears, between the couple, and between the legs. Much more investigation with control groups is needed to adequately further evaluate the effects of this therapy."

Wang had no conflicts of interest. Kandzari has served as an advisor or consultant for Boston Scientific, Medtronic, and Micell Technologies and has received grants for clinical research from Abbott, Boston Scientific, and Medtronic. Rogers has disclosed being a consultant for Volcano, St Jude Medical, Boston Scientific, and Medtronic.


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