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Heart Valve Design & Features

Every aspect of the On-X heart valve plays a role in maximizing benefits for the recipient. The scope of innovations in the design reflects On-X Life Technologies, Inc.’s commitment to perfection in creating the On-X Prosthetic Heart Valve.

Pure Carbon

Totally free of silicon. The purity and finish of On-X carbon coatings assures the greatest biocompatibility for the On-X valve design. The human body does not react against its pure carbon surfaces. Advanced processing technology yields highly polished and contoured features in the critical pivot area, which minimizes opportunities for clots to form or adhere.

Smooth carbon with no silicone results in reduced blood damage.

Heart Valve Design & Features: On-X pure carbon surface

Other Mechanical Valves
Silicon embedded carbon Rough surface increases chance of platelets sticking to surface blood damage.

other mechanical valve surface

Optimal Longer Length

The length-to-diameter ratio is similar to that of a native valve. Somewhat counter-intuitively, its greater length (or height) actually reduces turbulence and increases flow. It also allows for reduced leaflet excursion to reduce backflow losses, provides leaflet protection and protects the valve opening from tissue encroachment.

Short valves are vulnerable to tissue ingrowth (pannus) that can compromise valve function. On-X valves provide unprecedented protection from tissue impairments on both the inflow and outflow sides. The valve body extends fully through the annulus to preserve full functionality.


full annulus
The On-X valve provides full annulus support

The leaflet guards on the On-X valve extend the orifice to form an effective barrier, which protects the leaflet motion from impingement by tissue. This is particularly important in the mitral position when chordae tendineae are preserved. The On-X valve is the only valve with leaflet guards that offer this degree of protection.


Leavlet Guards
Leaflet Guard protects against impingement

Inlet Flared Orifice

On-X valve is the first prosthetic heart valve to successfully incorporate a flared inlet, the well-known fluid dynamic principle for producing smooth, organized flow with reduced turbulence. The flare produces an increased volume of flow, comparable to that of a larger orifice. Because the inlet flare extends through the annulus, it is not compromised by encroaching annular tissue and thus maintains the favorable annular shape for a lifetime of consistently optimal flow.

Full 90° Leaflet Opening

On-X valve leaflets are free to follow the flow. Other valves must stop short of the fully open position to ensure that they will close reliably with backflow, which can increase obstruction and turbulence.

With the On-X valve’s patented “actuated pivot design”, closure is assured even when leaflets are open to the full 90°. Leaflet freedom reduces turbulence and its accompanying effects such as pressure loss and blood damage.

Full leaflet opening

Stasis-Free Pivots

Complete non-hemolytic pivot purge. Pivots are a potential site of clot formation because of possible stasis (flow stagnation). The On-X design provides increased washing throughout the pivot to eliminate areas of potential flow stagnation.

Stasis-free pivots

Optimal pivot cleansing is accomplished by introducing flow paths between the leaflet and the pivot wall. The backflow channels are carefully designed to avoid hemolysis. Backflow over smooth, blended contours is key to the low thrombosis rate of the On-X heart valve.

Two-Point Closure

Distributes and minimizes closing impact. The On-X valve has patented two-point “soft landing” leaflets to reduce blood stress in three ways.

  • The two points are closer to the pivots so that the closing impact velocity is reduced by 40%.
  • The two-point landing distributes the closing impulse so that the impact is glancing rather than direct.
  • This “soft landing” minimizes the potential for cavitation that can damage blood.

Soft Landing also minimizes the potential for noise.


  1. Kae J., Ely Jl, Schwartz AS. Microstructural observations of pure pyrolytic carbons for heart valves. Twenty-second Biennial Conference on Carbon. J Transaction 1995:742-43.
  2. Bokros JC, Emken MR, Haubold AD et al. Prosthetic heart valve. US Patent No. 5,308,361: Issued May 3, 1994 and US Patent No. 5,137,532: Issued Aug. 11, 1992.
  3. Bokros JC, Ely JL, Emken MR et al. Prosthetic Heart valve with improved blood flow. US Patent No. 5,772,694: Issued June 30, 1998.
  4. Bokros JC, Ely JL, Emken MR et al. Prosthetic heart valve. US Patent No. 5,641,324: Issued June 24, 1997.
  5. Bokros JC, Stupka JC, More RB. Prosthetic heart valve. US Patent No. 6,096,075: Issued Aug., 1, 2003.