Mitroflow analysis finds early, frequent valve deterioration

French cardiac surgeons raised a red flag about the 12A/LX models of the Mitroflow valve, warning of a potential epidemic of structural valve deterioration and valve-related deaths in patients implanted with the devices.

Published online Oct. 29 in Circulation, Thomas Sénage, MD, and other physicians from University Hospital in Nantes, France, detailed findings from an analysis of 617 consecutive patients who underwent aortic valve replacement with a Mitroflow (Sorin Group) prosthesis between 2002 and 2007. Recent reports have questioned the durability of the valves, noting early structural valve deterioration, which prompted their study.    

The models assessed were the 12A and a later variation, the LX. Characteristics of the 12A model make it attractive for patients with a small aortic root. Physicians have implanted more than 100,000 Mitroflow valves in patients worldwide.

Almost two-thirds of the patients—396—received small diameter devices (19 mm or 21 mm). At a mean follow-up of 3.8 years, echocardiograms revealed 39 cases of structural valve deterioration. Sénage et al calculated that the probability of structural valve deterioration increased with time, from 0.2 percent the first year to 8.4 percent in year five.

“SVD [structural valve deterioration] is therefore an early and frequent finding in patients implanted with a Mitroflow bioprosthesis in the aortic position,” they wrote.   

Overall, five-year structural valve deterioration-free survival was 91.6 percent but it was only 79.8 percent with the 19 mm size.

Thirteen patients had what the researchers called “accelerated structural valve deterioration,” which they defined as an increase of the mean valvular gradient greater than 25 mmHg over a year. Six of these patients died of valve-related causes.

The five-year overall survival rate was 69.6 percent and structural valve deterioration increased the risk of death (hazard ratio 7.7). “With respect to the large use of Mitroflow prosthesis (>100,000 implantations worldwide), one can expect an epidemic of SVD requiring redo surgery or leading to death in these patients,” they predicted.

They called for annual echocardiographic testing after the first year of implantation and closer follow-up when a patient’s mean gradient hits 30 mmHg.

“Owing to the life threatening accelerated pattern of SVD in one third of patients, urgent reoperation should be considered once bioprosthesis stenosis is severe, even in asymptomatic patients,” they recommended.

Sénage et al noted that the 12A and LX lacked treatment designed to ward off calcification. In an accompanying editorial, Tsuyoshi Kaneko, MD, and colleagues at Brigham and Women’s Hospital in Boston wrote that the FDA approved a Mitroflow valve with phospholipid reduction therapy earlier this year. But, they added, whether it will prevent this kind of deterioration was unclear.

They reiterated the French team’s call for annual echocardiograms and aggressive treatment in cases of accelerated structural valve deterioration.