Mechanical heart valves provide much lower mortality than tissue valves in young patients

November 8, 2017- by Steven E. Greer, MD

Off the radar of Wall Street analysts is a new paper in the NEJM that shows mechanical heart valves, both aortic and mitral, impart much lower mortality than tissue valves in the youngest cohort of patients. This paper was not presented at the recent TCT or Euro PCR.

The results should be a negative headwind to TAVR growth in the low-risk younger patients, where most of the growth is modeled to be derived.  This paper also comes in the wake of emerging safety problems with TAVR involving clot formation (see video above).

From the abstract:

Mechanical or Biologic Prostheses for Aortic-Valve and Mitral-Valve Replacement

Andrew B. Goldstone, M.D., Ph.D., Peter Chiu, M.D., Michael Baiocchi, Ph.D., Bharathi Lingala, Ph.D., William L. Patrick, M.D., Michael P. Fischbein, M.D., Ph.D., and Y. Joseph Woo, M.D.

BACKGROUND In patients undergoing aortic-valve or mitral-valve replacement, either a mechanical or biologic prosthesis is used. Biologic prostheses have been increasingly favored despite limited evidence supporting this practice.

METHODS We compared long-term mortality and rates of reoperation, stroke, and bleeding between inverse-probability-weighted cohorts of patients who underwent primary aortic-valve replacement or mitral-valve replacement with a mechanical or biologic prosthesis in California in the period from 1996 through 2013. Patients were stratified into different age groups on the basis of valve position (aortic vs. mitral valve).

RESULTS From 1996 through 2013, the use of biologic prostheses increased substantially for aortic-valve and mitral-valve replacement, from 11.5% to 51.6% for aortic-valve replacement and from 16.8% to 53.7% for mitral-valve replacement. Among patients who underwent aortic-valve replacement, receipt of a biologic prosthesis was associated with significantly higher 15-year mortality than receipt of a mechanical prosthesis among patients 45 to 54 years of age (30.6% vs. 26.4% at 15 years; hazard ratio, 1.23; 95% confidence interval [CI], 1.02 to 1.48; P = 0.03) but not among patients 55 to 64 years of age. Among patients who underwent mitral-valve replacement, receipt of a biologic prosthesis was associated with significantly higher mortality than receipt of a mechanical prosthesis among patients 40 to 49 years of age (44.1% vs. 27.1%; hazard ratio, 1.88; 95% CI, 1.35 to 2.63; P<0.001) and among those 50 to 69 years of age (50.0% vs. 45.3%; hazard ratio, 1.16; 95% CI, 1.04 to 1.30; P = 0.01). The incidence of reoperation was significantly higher among recipients of a biologic prosthesis than among recipients of a mechanical prosthesis. Patients who received mechanical valves had a higher cumulative incidence of bleeding and, in some age groups, stroke than did recipients of a biologic prosthesis.

CONCLUSIONS The long-term mortality benefit that was associated with a mechanical prosthesis, as compared with a biologic prosthesis, persisted until 70 years of age among patients undergoing mitral-valve replacement and until 55 years of age among those undergoing aortic-valve replacement. (Funded by the National Institutes of Health and the Agency for Healthcare Research and Quality.)

We asked TAVR pioneer William O’Neill, MD of the Henry Ford Health System what he thought. He stated, “TAVR will be hurt by this in low risk patients. This is an important observational study that suggests younger patients survive longer if a mechanical valve is employed.

A major deficiency of the study is its observational nature. Typically, surgeons recommend mechanical valves in more robust patients. Frail, elderly patients, those who would have trouble with anticoagulation compliance or would be at increased bleeding risk with long term warfarin therapy have tissue valves recommended.

These biases confound analysis and this can only be dealt with in prospective randomized trials. For frail elderly patients, tissue valves seem equally safe and thus TAVR seems ideal for them.”

A Wall Street analyst who specializes in medical devices, who preferred to remain anonymous, stated, “It’s really interesting. The market has moved so much from mechanical to tissue over the last 15 years, because tissue valves have been lasting longer and patients don’t want to deal with (a) the anticoagulation required and (b) the noise of a mechanical valve. Historically, St. Jude was the leader in mechanical valves, followed by Medtronic, with Edwards the leader in tissue. But the mechanical side of the market has been contracting for years. I don’t think it impacts TAVR, but it may reverse some of the surgical mix shift that’s occurred the last 15 years.”


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