You’ll Never Look at Cows the Same Again
A cutting-edge new treatment involves a heart valve made of cow tissue.
There’s a cutting-edge new treatment for patients with aortic stenosis. It’s called transcatheter aortic valve replacement, and it’s less invasive than conventional surgical procedures.
TAVR’s integral component is the SAPIEN, a heart valve made of cow tis- sue, which is attached to a stainless-steel mesh frame that’s wrapped in polyester. Sound unappealing? Well, consider that earlier incarnations were made from pigs and other animals.
Aortic stenosis is the result of age, not clogged arteries. Most patients are in their 70s or older, and they usually have other illnesses or general frailties that disqualify them for traditional open-heart surgery. TAVR is performed in state-of-the-art, cardio-cath hybrid operating suites. Remarkably, it requires only an overnight hospital stay.
TAVR is currently approved only for elderly and high-risk patients. Created by Edwards Lifesciences, the SAPIEN valve has only been in use since 2011, when it received the FDA’s OK. Back then, it was inserted via catheter through the femoral artery or the lower tip of the heart. Thanks to new FDA-approved labeling, physicians can use alternate surgical methods for patients who require them.
Dr. Joseph Bavaria was one of the first surgeons to work with the SAPIEN valve. Bavaria’s position with Penn Heart and Vascular Center carries a few titles. He’s vice chief of the cardiovascular surgery division, director of the thoracic aortic surgery program, and co-director of the transcatheter valve program. All of that is brought to bear in the TAVR team he leads.
The SAPIEN is inserted into an artery or into the heart itself with a balloon catheter. Surgeons guide the catheter to the center of the diseased aortic valve, which is less than an inch in diameter. Half of the SAPIEN goes into the aorta, and half into the ventricle. The middle—what Bavaria calls the waist sits on the diseased valve.
Next, a pacer accelerates the patient’s heart rate. Surgeons momentarily stop blood flow to prevent blood from ejecting through the aorta while the valve is being installed. “Then we blow up the balloon, and the valve expands into the native valve,” Bavaria says. “It’s anchored into the spot like an hourglass, grabbing to the heart like handles. When we’re happy with its placement, we turn off the pacer, and the heart pumps normally.”
Experts point out that the catheter’s insertion and extraction can contribute to complications, possibly damaging the arteries through which it travels. Stroke is another risk of TAVR, as older patients often have calcium buildup in their arter- ies, and the catheter can knock it loose. Lankenau Heart Institute’s Dr. Scott Goldman puts the stroke risk at about two percent; Bavaria says it’s between two and six percent. For its part, the FDA has stated that patients who received a SAPIEN valve via TAVR “had three times more strokes” than those who didn’t get the device, adding that complications with the arteries leading to the legs were also more prevalent.
Because the diseased valve may be shaped differently than the SAPIEN, that anatomical mismatch can result in leakage around the valve, a condition that could be fatal if not corrected. The fix is open-heart surgery, says Bavaria—and for a patient who wasn’t a good candidate in the first place.
Naturally, making TAVR safer by improving both the artificial valve and the means of its delivery are twin goals at Penn Heart and Vascular Center. As director of the center’s interventional cardiology and cardiac catheterization laboratories, Dr. Howard Herrmann has been working with SAPIEN valves for more than a decade. He was involved with Edwards Lifesciences’ safety committees in 2003. “We did the first trial in the U.S. in 2007,” says Herrmann. “Now, we’ve done close to 700 procedures in seven years, making Penn’s the largest program in this area. One of the advantages is that we get a lot of newer devices.”
One of them is SAPIEN III, the valve’s third generation, which is now being used in Penn Medicine’s TAVR procedures. Bavaria and his team have tested other artificial valves in the FDA pipeline. They operate slightly differently and are made by other companies—competition that could lower the cost of TAVR. Right now, a surgical valve costs about $5,000, while a SAPIEN is six times that, says Bavaria.
Safer procedures and lower prices could radically change the field, making it suitable for many more patients. Before that can happen, there’s another issue to contend with: Prior SAPIEN research had only been done on high-risk patients. Trials involving low-risk patients are now in the works in the United States, but Europe is well ahead. “There, about 40 percent of valve replacements are done via TAVR,” says Goldman.