Cardiovascular implants of enhanced biocompatibility

DETAILED DESCRIPTION The invention provides cardiovascular and other medical implants of a low modulus, biocompatible, hemocompatible, metallic alloy of titanium with niobium and optionally zirconium.
The invention implants include heart valves, artificial hearts, ventricular assist devices, defibrillators, pacers, electrical leads, sensors, grafts, stents, and catheter devices.
The invention also provides surface hardened versions of these devices produced by oxygen or nitrogen diffusion hardening to improve resistance to cavitation, microfretting wear, and impact-induced wear.
The inherently low modulus of Ti--Nb--Zr alloys, between about 6 to about 12 million psi depending on metallurgical treatment and composition, provide a more flexible and forgiving construct for cardiovascular applications while improving contact stress levels, valve closure, and the ability of leaves in certain valve designs to self-align with blood flow and reduce thrombodynamic effects.
The invention provides components for use in mechanical heart replacement or assist devices, such as external mechanical hearts (EMHs), total artificial hearts (TAHs), and ventricular assist devices (VADs), that are lightweight, while also being resistant to corrosive body fluids, mechanical wear, abrasive wear, and microfretting wear.
Further, the components have much improved blood compatibility in the sense of reduced risk of thrombogenesis (blood clotting).
The preferred low modulus titanium alloys of the invention have the compositions: (i) titanium; about 10 wt.
% to about 20 wt.
% niobium; and optionally from about 0 wt.
% to about 20 wt.
% zirconium; and (ii) titanium; about 35 wt.
% to about 50 wt.
% niobium; and optionally from about 0 wt.
% to about 20 wt.
% zirconium.
Tantalum can also be present as a substitute for Nb.
These alloys are referred to herein as "Ti--Nb--Zr alloys," even though tantalum may also be present.
The exclusion of elements besides titanium, zirconium, and niobium, or tantalum results in an alloy which does not contain known toxins or carcinogens, or elements that are known or suspected of inducing diseases or adverse tissue response in the long term