Baltimore, MD - Percutaneous aortic-valve (AV) replacement can't come soon enough? Not to worry: authors of a new study say a minimally invasive alternative to surgical AV replacement (AVR) already exists and could be used now to treat the thousands of high-risk patients with aortic-valve stenosis who are being turned away from conventional AVR surgery [1].

According to Dr James Gammie (University of Maryland Medical Center, Baltimore) and colleagues, AV bypass surgery is a time-tested but little-used option for patients with high-risk aortic-valve stenosis that, with practice, can be done off-pump through a three-inch incision. The apicoaortic conduit used in the procedure is made up of components already approved for the procedure, and the operation itself has existing CPT and ICD-9 codes.

"This operation has been around a long time, but it was never widely disseminated," he told heartwire. "It's been a largely unknown operation."

According to Gammie and his coauthors, the first clinically successful AV bypass was done in the early 1960s, but the procedure was eclipsed within a few years by the now-standard AVR surgery. Interest in AV bypass was rekindled somewhat in the 1970s with the development of the apical connector used to treat complex congenital left ventricular outflow tract obstruction in children, but, as Gammie told heartwire, AV bypass today is likely performed just 20 times per year and by very few surgeons.

The procedure involves two anastomoses, one to the descending aorta and one to the heart, Gammie explains. "The one to the heart is the tricky one, and that's where we've had a little bit of a learning curve, but now that we do it routinely, we're very, very comfortable doing it without the heart-lung machine." The apicoaortic conduit is made up of three parts: a rigid stented apical connector with a sewing ring that gets inserted into the LV apex; a stentless porcine valve; and a Dacron graft.

"We put a partial clamp on the descending aorta and we sew our graft down there, and then we take that off and scoop it up like a periscope, and then we bore a hole in the tip of the heart, pull out the plug of heart muscle, pop our finger in there, stick the connector in, and sew it in place," Gammie explained. "One of the reasons people have not thought about doing this, or have perhaps been put off by it, is that it sounds sort of like a brutal procedure. But in fact it can be done very safely, and we're now doing this through a less invasive incision—the last four patients I've done have been done through a three-inch incision."

In their paper, Gammie et al describe outcomes for 31 high-risk aortic-valve stenosis patients, mean age 81, who underwent the procedure. Overall, perioperative mortality was 13% (four patients) but no perioperative deaths occurred in the last 16 patients of the series. No strokes occurred during follow-up, although one stroke occurred perioperatively, due to intraoperative hypotension. Overall, left ventricular outflow tract obstruction was relieved, and there were no signs that LV function was compromised by the insertion of the conduit; renal function was also unchanged.

To heartwire, Gammie emphasized that the patients in their series were elderly and frail, with multiple comorbidities. "They really make up a small number of patients that we do," he said. "But my belief is that we should contemplate extending this operation to moderately high-risk patients, based on our findings that stroke and renal dysfunction are uncommon."

He and his colleagues are currently planning a clinical trial that would randomize moderate- to high-risk valvular aortic-stenosis patients to either conventional AVR surgery or AV bypass surgery.

Gammie acknowledges that the excitement over the percutaneous/transcatheter valve replacement has really refocused awareness on the sheer volume of aortic-stenosis patients who are not referred for surgery, a number that approaches 60%, he said. Realizing the potential for transcatheter valve to encroach on their surgical referrals, many surgeons have taken an if-you-can't-beat-'em-join-'em attitude and are learning catheter skills and teaming up with interventionalists to be more closely involved in transcatheter valve development. The PARTNER trial, testing the Edwards percutaneous aortic valve against surgical AVR and best medical therapy, has recently ramped up enrollment in the US.

But Gammie believes that AV-bypass surgery would likely compete directly with transcatheter aortic-valve replacement and indeed has several advantages.

For one, a wide range of valve prosthetics can be used in the apicoaortic conduit—those used in Gammie et al's study have a long track record of safety and durability, he notes. Likewise, the procedure itself, while not widely used, has proven its durability. "There are people walking around today who had this operation a quarter century ago," Gammie points out. "So we know it's a durable approach."

Third, there is no disruption to the native valve and no permanent prosthetic forced over the calcified valve leaflets, thus reducing the risk of both perioperative and long-term stroke. There's also no risk of heart block—a side effect seen following the implantation of permanent percutaneously placed devices, Gammie notes. Finally, perivalvular leak is not a potential problem, since the device does not need to be sized within the native valve. "So patient-prosthetic mismatch is not a problem," he said.

On a more hypothetical note, Gammie said that he and his colleagues are testing whether diverting blood flow away from the calcified native valve would in itself decrease stroke rates over the long term. Preliminary analysis suggests that roughly two-thirds of the blood volume may be diverted through the conduit, a rerouting that may prove beneficial over time. "Our hypothesis, which we haven't proven yet, is that AV bypass surgery may be 'brain-protective,' because of the blood flow configuration in the long term," he speculated.

Asked to comment on the procedure for heartwire, Dr Craig Smith (Columbia University, New York, NY), co-principal investigator for PARTNER, agreed that AV bypass is "reemerging somewhat."

"At Columbia, we've started doing these again in the past year largely to accommodate disaster patients referred for the [PARTNER] trial who are ineligible and conventionally inoperable," Smith explained, adding that one member of his group has been doing some "very creative things" with apicoaortic conduits in the cath lab. But on the whole, he predicted, AV bypass will likely remain a "niche procedure."

"Transcatheter valves will probably capture the truly high-risk population as soon as they're released, with seepage into moderate-risk patients over time," he said.

Craig's co-PI for PARTNER, Dr Marty Leon (Columbia University), agreed. "[AV bypass] is a little-used, 'old' procedure for good reasons, not the least of which is procedural complexity, high complication rates, and little long-term favorable clinical outcome data," he told heartwire. "I'm not at all concerned that this old surgical procedure constitutes a threat to the emerging transcatheter AVR procedure."

But Gammie, for his part, says there has been a "groundswell of interest and enthusiasm" for AV bypass surgery, accompanied by an uptick in the number of surgeons coming to Baltimore to learn the procedure from his group. "The thing that's prevented widespread adoption of this procedure is that people say, 'Well gee, I don't want to cut a hole in a person's heart,' " he explained. "But with practice, it's not that hard and it's quite safe."

Gammie has also been involved in the development of a device used to core into the apex of the heart and insert the connector "in one fell swoop," something he believes will greatly simplify the procedure and make it safer. The device was not used in the current study, Gammie clarified, although he is a founder of the company, Correx, now testing the device in animals. Gammie also consults for Medtronic, which manufactures the apical connector used in the study.