Transcaval TAVR Presents New Option for Patients With Complex Anatomy

WASHINGTON, DC—For patients eligible for TAVR but contraindicated for femoral artery access, a new extra-thoracic, percutaneous technique of reaching the abdominal aorta through transcaval access—circumventing peripheral obstructions—may offer an alternative.

This method, in which the operator enters the abdominal aorta by electrifying a caval guidewire, advancing a prepositioned aortic snare, performing conventional TAVR through introducer sheaths, and finally closing the access ports with nitonol cardiac occluders, was designed to avoid the “discomfort and morbidity” of established transthoracic access methods, including transapical and transaortic, write study authors led by Robert J. Lederman, MD (National Heart Lung and Blood Institute, Bethesda, MD). Full results were published today in the Journal of the American College of Cardiology and will be presented Monday here at TCT.

Yet transcaval access “falls into the category of ‘don’t try this at home,’” said Michael Mack, MD (The Heart Hospital Baylor, Plano, TX), who was not involved in the study but has observed cases that used the technique. “Although I congratulate the investigators on this very innovative approach—it is ingenious, I must admit—I think that there are other less invasive alternatives when you can't do a transfemoral approach, which is a small minority of patients currently,” Mack told TCTMD.

Specifically, he said his team has tried both transapical and transaortic access for this patient population but has since switched to subclavian access. The group is also investigating “a new option that you can go through a small incision in the neck and directly into the aorta,” Mack noted.

However, interventional cardiology fellow Ateet Patel, MD (Emory University, Atlanta, GA), told TCTMD that while the idea of transcaval access is “jarring,” with “very good planning” it can be “relatively seamless” to execute.

When the idea for transcaval access for TAVR was first proposed 3 years ago, co-author Adam Greenbaum, MD (Henry Ford Hospital, Detroit, MI), told TCTMD that ”anybody we talked to said it couldn’t be done, the patients would die immediately, and that it would be heresy basically.” But with the results of this study, he hopes more doubters will become believers. “As far as I’m concerned, if you are a large-volume [TAVR] center, you ought to be able to do [all access methods],” Greenbaum added.

Favorable Findings

In the study, given investigational device exemption by the US Food and Drug Administration for the Amplatzer nitinol occluders (St. Jude Medical), the primary endpoint of device success—successful transcaval access and deployment of a closure device without death or emergency open abdominal surgery—was achieved in 98 of 100 patients treated at 20 US sites between 2014 and 2016. In one patient the guidewire failed to cross and the operator converted to transfemoral TAVR complicated by iliac artery rupture, and in another the operator chose primary closure using a covered aortic stent instead of the nitinol occluder.

There were no periprocedural deaths and no emergency abdominal surgeries, but there was one case of valve-related coronary obstruction that turned fatal, one case of aortic annular hematoma, and 16 new permanent pacemakers. Thirty-day survival was 92%, and rates of VARC2-defined life-threatening bleeding and major vascular complications possibly related to transcaval access were 7% and 13%, respectively.

As for the physiology that allows the procedure to work, Greenbaum explained that “the venous system is lower pressure than the surrounding tissue, . . . so if you have a hole in both the aorta and a hole in the [inferior vena cava (IVC)], then the blood actually goes from the aorta to the IVC but stays intravascular. It doesn't actually bleed. So that physiologic principle allows the catheter to be withdrawn and then for a plug to be placed on the aortic side to eventually wall off the hole.”

The findings were “remarkable given that most participating centers had limited prior transcaval experience, that we employed a permeable closure device, and that the patients had extensive comorbidity,” Lederman and colleagues write. “From a patient-centered outcome perspective, the primary observed morbidity, of blood transfusions, compares favorably to the morbidity of surgical transthoracic access.”

Compared with other nontransfemoral access options, the authors write that transcaval access could provide “superior operator ergonomics, in that the operators work from the standard right groin puncture site; less tortuous sheath trajectory; less risk of brachial plexus injury; no surgical dissection.” That said, they say, “all of these extra-thoracic access methods appear to work well.”

‘It’s Readily Learnable’

Still, Mack isn’t convinced, especially given the expertise required to perform a TAVR procedure in this manner. “The adoption of any medical procedure is directly related to how operator-friendly it is,” he said. “This is a procedure that does give very admirable results in the hands of experts right now. My question is how scalable this is, how expandable this is to the 470 centers in the United States that are doing TAVR.”

Greenbaum said about 30 US centers are currently proficient in this access method and that operators new to it typically take two to three cases to be comfortable on their own. Most of the skills they use for transcaval access are “things that most structural interventionalists are comfortable doing already,” he argued.

Looking beyond TAVR, Patel said transcaval access can have applications in “the endovascular space for aortic pathology as well as support devices.” He explained that for patients in shock “we like to leave [support] devices in longer, so the idea of having a large sheath in a femoral artery or something like that obviously poses some other risks. For that reason [transcaval access] may grow as a technique even if it doesn’t grow a ton within the TAVR space.”

As for the “steep” learning curve, Patel said that even as a “new trainee in this technique,” which he has now used for TAVR, Impella support, and endovascular abdominal aortic aneurysm repair, “it’s readily learnable.”