As Technique Inches Forward, Outcomes Improve for Transcatheter Treatment of Severe Calcific Mitral Disease

PARIS, France—Updated results from the Mitral Annular Calcification (MAC) registry reaffirm that the use of transcatheter aortic valves in the mitral position for severely calcified mitral disease remains an extremely high-risk procedure. 

But as Mayra Guerrero, MD (Northshore University HealthSystem, Evanston, IL), showed today during a hotline session at EuroPCR 2016, technical proficiency and outcomes appear to be improving. 

“And why?” Guerrero said in an interview with TCTMD. “Because we are screening better, because now we’ve learned from the early experience what to look for and when to say no. And we’ve learned how to treat the complications using options we didn’t know about before.” 

Surgical mitral valve replacement for severely calcified mitral valve annuli remains a very high-risk, technically challenging procedure, and many patients go untreated, facing low survival with conservative management. For several years and in select, compassionate use cases, interventional cardiologists have attempted to treat severe calcific mitral valve disease using transcatheter valves designed for use in the aortic position. Outcomes for these compassionate use patients are being tracked in the MAC Global Registry. 

At CRT 2016, Guerrero presented results on 81 patients from 40 centers, as reported by TCTMD. In this group, technical success was 76.5% and 30-day mortality was 9.9%. 

In a new presentation, Guerrero revealed results for 104 patients treated at 47 centers in 11 countries. Findings from the larger patient series suggest that technical success and complication rates remain similar, but that the mortality rate is edging downwards. In the expanded series, 25% of patients had died within 30 days; of those deaths, 9.6% were cardiovascular in nature. 

In an analysis that looked at clinical outcomes relative to cumulative experience with the procedure, Guerrero showed that technical success increased from just 62.5% in the first 32 patients treated to 80% in the most recent 40 patients. In parallel, mortality declined from 37.5% in the earliest patients to 15.0% in the most recently treated patients.  

Of note, left ventricular outflow tract (LVOT) obstruction, which remains the most important complication with this procedure, has remained relatively constant at 10.5%. But Guerrero said operators have become better at treating it. She reported that six patients were treated with alcohol septal ablation as bailout, achieving a reduction of LVOT gradient in each case. Two patients died within weeks of their complication, but four of the six patients who experienced LVOT obstruction during valve implantation were subsequently discharged from the hospital.  

Notably, cardiac perforations and conversion to open surgery, which occurred respectively in two patients and four patients among the initially treated group, have not occurred among the 72 patients subsequently undergoing the procedure.  

An Unmet Clinical Need

Speaking with TCTMD, Guerrero stressed that this is a specific subset of patients with very severe mitral valve disease, namely patients with “a real donut of calcium” in the mitral annulus. As such, they are not patients who would be suitable for the dedicated mitral valves currently in development, but the calcium, as in aortic valve disease, offers a means of anchoring a transcatheter valve like those developed for aortic stenosis.    

Indeed, in discussing the hotline results, Nicolo Piazza, MD (McGill University Health Center, Montreal, Canada), reiterated that there are no specific devices for severely calcified mitral valves. “This definitely represents an unmet clinical need,” he said. 

He noted that patients in this registry are much younger (mean age 73 years) than the patient population treated in the early PARTNER trials for aortic valve stenosis, with a higher proportion of women (66%). They are also very high-risk, with a mean STS score of 14.4.   

Limitations of the study, Piazza continued, relate to the fact that this was a real-world registry where patient selection and physician bias may have influenced the results, as would a lack of standardized exclusion and inclusion criteria.  

Guerrero and colleagues have received FDA approval to proceed with a multicenter, physician-sponsored, IDE pilot study known as the Mitral Implantation of Transcatheter Valves (MITRAL) trial. The study will enroll 90 patients at 10 US sites and will include three arms: a native calcific mitral stenosis group, a valve-in-ring group for failing surgical rings, and a valve-in-valve group for a failing bioprosthesis. 

For each arm, candidates will have to be nonsurgical candidates, as decided by trial investigators as a group, rather than at individual centers. As Guerrero explained to TCTMD, the trial will have a clinical event committee, a data safety and monitoring board, and independent core lab adjudication. The echo core lab will be at Duke University, Durham, NC, and the cardiac CT core lab will be at Henry Ford Hospital, Detroit, MI. 

To TCTMD, Guerrero said that she believes outcomes have improved in part because of better discussion between different centers attempting this high-risk procedure. 

“If we work together, we might be able to improve outcomes even further,” she said. 

Source:

• Guerrero M. Transcatheter mitral valve replacement in native mitral valve disease with severe mitral annular calcification. Presented at: EuroPCR 2016. May 17, 2016. Paris, France. 

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