Renal Artery Interventions: An Interview With Larry J. Diaz-Sandoval, MD

Editor's note: See related video.

Larry J. Diaz, MD, is an interventional cardiologist at Metro Health Hospital in Wyoming, Michigan. He performs interventional peripheral vascular procedures and specializes in critical limb ischemia. Dr. Diaz spoke on the topic of renal artery interventions at the 2014 New Cardiovascular Horizons meeting in New Orleans. Vascular Disease Management asked him a few questions about his presentation and the latest information on therapy for renal artery interventions. Dr. Diaz shares his comments below.

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Q: Could you summarize your presentation on renal artery interventions?

A: At New Cardiovascular Horizons (NCVH) in New Orleans I addressed the current status of renal artery denervation and renal artery stenting, which is undoubtedly a daunting task given the current status of these two therapies. As we all know, the results of SYMPLICITY HTN-3 came back negative for renal artery denervation. There are several reasons as to why these studies have been negative. One point that has been addressed is the fact that in the current study, SYMPLICITY HTN-3, the catheter that was utilized was different than the catheter that was utilized during the SYMPLICITY HTN-1 and SYMPLICITY HTN-2, which were performed in Europe. Another issue was the fact that 33% of the population in SYMPLICITY HTN-3 was African American, and these patients were rarely seen or evaluated as part of the first two studies. 

Another issue was operator experience. Approximately 60% of the procedures were performed by operators who performed only 1 or 2 procedures with the new catheter, and the catheter has been reported to be difficult to maneuver, making the procedure technically more demanding. Another issue with the SYMPLICITY HTN-3 study is that the operator does not have immediate feedback as to whether or not the burn that is being performed by the radiofrequency catheter is technically effective. Because the new catheter was difficult to maneuver, there has been discussion about whether the amount of pressure that could be exerted with the tip of the catheter into the intima was not sufficient to generate a deep enough burn to effectively ablate the nerve in the adventitia. 

Furthermore, one of the criteria during the SYMPLICITY HTN-3 study was that there should be no changes in medication so that patients were stable in their current medication regime. There were, however, many changes to the medication regime that these patients had. The general sentiment is that if these patients had changes to their medication regime, they were actually not at maximum tolerated doses of the blood pressure medicines, which was one of the criteria to include them in the study. 

In summary, I do not think that renal artery denervation is gone. I prefer to think that this is actually a renaissance for renal artery denervation as this experience has opened our eyes as to how to avoid these flaws in upcoming studies. 

There are also other modalities, such as renal artery denervation through chemical injection in the adventitia, which was reported here at NCVH by Timothy A. Fischell, MD, as being very effective. This is very exciting. We have a very good outlook at this study that is supposed to come to the United States in 2015, and the status of future studies changes on a daily basis.

Q: What were some key points on the status of renal artery stenting?

A: When I spoke about renal artery stenting, I told the audience the status was a bit depressing. When the results of the CORAL study were published the interventional community felt a hit when it came to renal artery stenting. There have been many flawed randomized controlled clinical trials in renal artery stenting. Although CORAL was well conducted, it did not address what happened to those patients who failed medical therapy. According to the reigning guidelines, renal artery stenting is appropriate and should be reserved for patients who fail medical therapy and have a renal artery stenosis of more than 70% or that have an intermediate lesion of 50% to 70% with proven hemodynamic compromise (translesional gradient of at least 10 mmHg or 20 mmHg during hyperemic conditions or in patients with FFR measured at less than 0.8). 

The patients who fail medical therapy are the patients we want to study to see if renal artery stenting is going to make a difference. We are left still with current recommendations. Unfortunately the possibility of securing more federal funding to perform further studies like this is unlikely and therefore we will continue to have to use our clinical judgment in this particular cohort of patients.

tive of cerebral gas embolism seen in any of the patients treated with Varithena.

It’s important to understand the safety of any sclerosant because many providers with a pure surgical background may fear the use of foam. Image guidance is imperative to allow adequate visualization to track where everything communicates and not only assure that the target vein has been exposed, but that normal veins have been protected. With proper care, it’s an incredibly safe tool to employ, though it does have a learning curve. 

When it comes to efficacy, I’ve been treating veins for over 12 years and I started by using sclerosants to treat veins. Although you can treat incompetent saphenous veins and close them with a number of different sclerosants, it requires far more treatment sessions with far greater side effect profiles than what Varithena presents. So if you were to look at the efficacy results in recent trials, 80% of people had complete closure of the target vessels with one treatment and that’s pretty striking for a sclerotherapy agent. All of the patients that I treated as part of a phase-3 FDA trial using Varithena said they would do it again. When it came to what I was able to see on those patients with regards to their symptom control and what we saw on Duplex not every patient had the same response, of course, because we were using a variety of different concentrations; it was a randomized and blinded trial. At the same time, when we discovered what we initially gave these patients I was quite impressed as far as the response we saw even to some of the lesser concentrated chemicals. 

When you look at efficacy you have to look at a couple of different things. Are you talking about closure of the vein or are you talking quality-of-life improvement? The surrogate outcome of vein closure with one treatment at 80% is pretty strong, but when you look at quality-of-life benefits that these patients reported, I think that’s even more striking. It seems as though much of the research available compares device A to device B in terms of results on ultrasound, not necessarily in terms of benefit to the patient when it’s done. And that’s the one thing that the research behind Varithena has brought forth clear as can be: the patients treated with Varithena can have a very significant change in their quality of life for the positive.