PARIS (FRONTLINE MEDICAL NEWS) – Transcatheter mitral valve replacement using a repurposed transcatheter aortic valve in patients with severe symptomatic native mitral valve disease and severe mitral annular calcification is feasible and may be an option in carefully selected patients who aren’t candidates for surgery, Mayra Guerrero, MD , said at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

However, at this early point in development, the procedure is associated with an exceptionally steep learning curve, said Dr. Guerrero, director of cardiac structural interventions at the NorthShore University Health System in Evanston, Ill.

She presented the procedural and 30-day outcomes for the first 104 patients entered into a global registry encompassing 47 centers in 11 countries. Nearly 90% of patients received an Edwards SAPIEN XT or SAPIEN 3 valve. The EuroPCR results update an earlier report on the first 64 patients in the registry ( JACC Cardiovasc Interv. 2016 Jul 11;9[13]:1361-71 ).

The results, she said, are reminiscent of the early days in transcatheter aortic valve replacement, which were marked by an initial very high early mortality rate that fell dramatically as technology and techniques improved.

“We know that there are important things we need to improve. Left ventricular outflow tract obstruction is the Achilles heel of this procedure; we need to work on its prevention and management. We need better annulus sizing methods. We need to find the best delivery method and improve our patient selection in order to avoid taking on patients who are too sick. Still, even during this early experience, the technical success rate has improved, and 30-day mortality continues to drop,” Dr. Guerrero said.

Indeed, the 30-day all-cause mortality rate of 25% in the first 104 patients doesn’t tell the whole story. The rate was 37.5% in the first third of patients, fell to 21.9% in the second tertile, and then to 15% in the most recent tertile.

Similarly, the technical success rate of the procedure according to Mitral Valve Academic Research Consortium criteria improved from 62.5% in the first tertile of patients to 84.4% and 80% in the second and third, respectively, she continued.

The rates of almost all complications went down with greater operator experience, too. The notable exception was left ventricular outflow tract obstruction (LVOTO). It occurred in 12.5% of patients in the first tertile and remained unchanged in the third.

It’s noteworthy that the majority of deaths were noncardiac in nature. Patients with mitral annular calcification are a high-risk group even before they develop valvular dysfunction. They are typically older and have multiple comorbidities. Participants in the global registry had a mean Society of Thoracic Surgeons score of 14.4; 38% had diabetes, 45% had chronic obstructive pulmonary disease, 35% had heart failure, 34% had previously undergone coronary artery bypass surgery, and roughly half of patients had a prior aortic valve replacement.

Causes of noncardiac mortality within 30 days included multiorgan failure in 8.6% of subjects, pneumonia in 2.9%, infection in 1.9%, and one fatal thoracentesis-related bleeding complication.

Cardiovascular deaths included two cases due to left ventricular perforation, two fatal strokes, an MI due to air emboli, a lethal complete atrioventricular block, and three deaths owing to LVOTO.

Alcohol ablation met with some success as a bailout treatment in cases of LVOTO with hemodynamic compromise after transmitral valve replacement in the global registry. All six treated patients had significant improvement initially, although the LVOTO recurred the next day in one instance. Four of the six patients were discharged from the hospital. One patient died because of atrioventricular block, and another from multiorgan failure 3 weeks after alcohol ablation of the LVOTO.

Dr. Guerrero has been a leader in this new field. She reported the first percutaneous implantation of a balloon expandable transcatheter valve in a native mitral valve without a surgical incision ( Catheter Cardiovasc Interv. 2014 Jun 1;83[7]:E287-91 ), and more recently, together with coworkers developed a percutaneous alcohol ablation technique for acute reduction of LVOTO due to transcatheter mitral valve replacement (Catheter Cardiovasc Interv. 2016 Jul 5. doi:10.1002/ccd.26649).

She is now the principal investigator in the ongoing Mitral Implantation of Transcatheter Valves (MITRAL) trial, a physician-sponsored, 90-patient pilot study underway at six U.S. sites. MITRAL is recruiting three patient populations for transcatheter mitral valve replacement: patients like those in the global registry, with native mitral valve disease and severe mitral annular calcification; those with a symptomatic failing surgical ring with severe mitral regurgitation or stenosis; and patients with a symptomatic failing surgical bioprosthesis with severe mitral regurgitation or stenosis.

Discussant Nicolo Piazza, MD , of McGill University, Montreal, said transcatheter mitral valve replacement in mitral valve disease with severe mitral annular calcification in patients unsuitable for surgery “definitely represents an unmet clinical need in our practice today.” But he urged caution in interpreting the global registry data.

“This is a real world registry study with inherent selection bias and physician reporting bias,” the cardiologist said.

“We are leveraging a therapy from the aortic field into the mitral field. Of course, we do not have dedicated devices yet to treat these patients. The main finding of this study is that the procedure is actually feasible,” Dr. Piazza said.

Still, it’s sobering that at least 1 in 10 treated patients experiences LVOTO, 1 in 10 requires a second valve, and technical success is achieved in 3 out of 4 patients, he added.

Dr. Piazza predicted that multislice CT scans will be “extremely important” in refining patient selection criteria for the procedure, and echocardiography will be helpful in understanding the optimal procedural techniques and viewing angles. Work also needs to be done on developing optimal anticoagulation protocols in order to avoid valve thrombosis.

Dr. Guerrero reported serving as a consultant to Edwards Lifesciences. Dr. Piazza is a consultant to Medtronic and MicroPort.