Invention of Artificial Heart Valve: Mechanical Life Support History

The artificial heart valve was not invented in one event by one person. Charles Hufnagel proved in 1952 that a synthetic caged-ball valve could function in the human circulation, but his device sat in the descending aorta rather than replacing the damaged valve. True intracardiac replacement followed after cardiopulmonary bypass made open-heart surgery practical. In 1960, operations by Dwight Harken, Nina Braunwald and Albert Starr established different clinical milestones, while Starr’s partnership with engineer M. Lowell Edwards produced the first widely adopted, durable mechanical heart valve.

Why a Replacement Valve Was So Difficult to Build

A natural heart valve is thin, flexible and responsive to very small pressure differences. It must open with little resistance, close rapidly without permitting substantial backflow and repeat this cycle tens of millions of times each year. Its surfaces are continuously exposed to blood, while its edges and supporting tissue absorb changing loads with every heartbeat.

A mechanical replacement did not need to resemble natural anatomy, but it had to reproduce the same one-way function. The moving element could not jam, fracture or wear rapidly. The housing had to remain anchored to living tissue, and every blood-contacting surface had to limit damage to blood cells and discourage clot formation.

The surgical problem was equally severe. Before dependable cardiopulmonary bypass, opening the heart long enough to remove a valve and sew in a substitute was not generally survivable. A practical artificial valve therefore depended on a system of innovations: extracorporeal circulation, improved anesthesia, blood management, sterile technique, sutures, implantable textiles and postoperative care.

Hufnagel’s Valve: A First Step Outside the Heart

Charles Hufnagel approached aortic regurgitation without opening the heart itself. In this condition, the aortic valve fails to seal properly, allowing blood to return toward the left ventricle after each contraction. Hufnagel placed his prosthesis in the descending thoracic aorta, where it could interrupt part of this reverse flow.

The device contained a freely moving ball inside an acrylic chamber. Forward blood flow pushed the ball away from its seat. When pressure reversed, the ball returned to the opening and sealed it. A cage retained the ball while allowing blood to pass around it.

This arrangement could not stop regurgitation into the coronary arteries or vessels supplying the upper body because those branches arose upstream from the implant. It also offered little help for a narrowed native aortic valve. Even so, the operation provided critical evidence: an artificial occluder could cycle in blood, remain mechanically contained and support a living patient.

Cardiopulmonary Bypass Changes the Surgical Boundary

The decisive enabling technology was the heart-lung machine. During cardiopulmonary bypass, venous blood is diverted to an external circuit, oxygenated and returned to the arterial circulation. The machine temporarily performs the pumping and gas-exchange work normally handled by the heart and lungs.

John Gibbon’s successful 1953 repair of an atrial septal defect showed that extracorporeal circulation could support a patient during an intracardiac operation. Other surgeons and engineers then refined pumps, oxygenators, tubing and operating methods. By the end of the decade, teams could stop and open the heart under controlled conditions, remove severely damaged valve tissue and attach a prosthesis to the remaining annulus.

This was the transition from adding an auxiliary valve elsewhere in the circulation to replacing the failed structure at its anatomical position.

The Multiple Valve-Replacement Firsts of 1960

Several teams reached important but distinct milestones in 1960. Dwight Harken performed an aortic valve replacement with a caged-ball device in March. The prosthesis was placed below the coronary openings, where it directly assumed the one-way function of the removed aortic valve.

Nina Braunwald implanted a flexible polyurethane mitral prosthesis during the same period. Her design used artificial leaflets and chord-like supports rather than a captive ball. It demonstrated that total mitral replacement was possible, although the materials and flexible construction of early leaflet prostheses presented durability challenges.

Albert Starr’s September operation with the Starr–Edwards valve supplied the landmark most often associated with successful mechanical mitral replacement. The patient survived long term, returning to an active life before dying years later from an unrelated accident. Starr and Edwards subsequently reported a series in which six of the first eight patients survived surgery.

How Starr and Edwards Turned a Prototype into a Product

M. Lowell Edwards initially wanted to develop a complete artificial heart. Starr, a cardiac surgeon at the University of Oregon Medical School, proposed beginning with a single valve. Their collaboration joined hydraulic engineering with operative observation: Edwards could rapidly build and alter mechanisms, while Starr could identify anatomical, flow and implantation problems.

The team initially explored designs that imitated natural leaflets. They eventually abandoned anatomical resemblance in favor of a mechanically simpler ball-and-cage system. The ball was unattached and could rotate, distributing contact and wear instead of repeatedly loading one hinge or edge.

The established Starr–Edwards models used a silicone elastomer ball retained by a cobalt-alloy cage. A polyester fabric sewing ring allowed the surgeon to anchor the valve to tissue. The cage geometry gave the ball enough travel to open the orifice while preventing its escape.

Clinical production required more than a working shape. Components needed consistent dimensions, smooth surfaces and predictable material properties. Early models were repeatedly modified in response to thrombosis, leakage, tissue overgrowth, blood-cell damage and wear. This feedback loop converted a hand-built experimental prosthesis into a controlled medical product.

How a Caged-Ball Mechanical Valve Works

1. Forward pressure risesPressure on the inlet side exceeds pressure beyond the valve and pushes the ball away from its circular seat.
2. The flow path opensThe cage limits ball travel while blood moves through the annular space between the displaced ball and valve housing.
3. Pressure reversesAs the pumping chamber relaxes, downstream pressure becomes greater and drives the ball back toward the inlet.
4. The seat closesThe ball contacts the circular seat and blocks reverse flow until the next pressure cycle begins.

The mechanism was robust, but the ball occupied the middle of the flow stream. Blood had to accelerate around it, creating regions of high velocity, turbulence and recirculation. The prosthesis was also relatively tall and heavy compared with later designs. These characteristics encouraged engineers to search for lower-profile occluders.

Why Materials Determined Clinical Survival

Pyrolytic carbon became especially important. Originally developed for high-temperature technical applications, it was adapted for valve components by materials engineer Jack Bokros and collaborators during the 1960s. Carbon coatings and structures offered the wear resistance required for billions of repeated cycles while producing a blood-contacting surface better suited to implantation than many early polymers and bare metals.

From Caged Balls to Tilting Discs

The next major design family replaced the central ball with a circular disc. In a tilting-disc valve, pressure rotates the disc around an offset pivot. The open disc divides the flow into a larger and a smaller passage rather than forcing all blood around a large spherical obstacle.

The Björk–Shiley valve, introduced clinically in 1969, became one of the best-known examples. Other designs, including the Lillehei–Kaster and Medtronic-Hall valves, altered the pivot, opening angle and housing. Their lower profile made implantation easier in restricted anatomical spaces and generally improved forward-flow performance.

The generation also demonstrated that small manufacturing details could have life-or-death consequences. Certain later Björk–Shiley convexo-concave models experienced outlet-strut fractures that could release the disc and cause sudden valve failure. The episode reinforced the need for fatigue testing, process control, traceability and long-term device surveillance.

Why the Bileaflet Design Became Dominant

A bileaflet valve uses two semicircular plates mounted in pivots within a circular housing. When open, the leaflets form three principal flow channels. When pressure reverses, both rotate closed against the housing.

The model developed for St. Jude Medical was the first all-pyrolytic-carbon bileaflet valve in clinical use, with its first surgical implantation recorded in October 1977. Its compact form and comparatively unobstructed opening provided better central flow than a caged ball. Pyrolytic-carbon leaflets and housing surfaces supplied the durability needed for lifelong cycling.

Later bileaflet valves refined the hinges because the pivot region is both mechanically essential and vulnerable to stagnant flow. Designers shaped the housing and leakage paths so small reverse jets could wash the hinge areas during closure. These controlled flows help clear blood from regions where clotting might otherwise begin, although they cannot make the device completely non-thrombogenic.

Mechanical Valve Versus Tissue Valve

These are not simply old and new versions of the same invention. They are different engineering compromises. Mechanical valves prioritize structural durability. Tissue valves more closely reproduce flexible leaflet motion and can simplify long-term medication requirements, but they have a finite risk of structural degeneration.

What the Mechanical Valve Changed

Before dependable valve replacement, advanced valvular disease could progress beyond the reach of repair. A mechanical prosthesis gave surgeons a way to remove a structure that no longer opened or sealed and replace its essential function with a manufactured mechanism.

The achievement also altered medical-device engineering. Heart valves demanded fatigue resistance measured over billions of cycles, precise control of blood-contacting surfaces and close coordination between surgeons, materials specialists and manufacturers. Lessons from valve development influenced later work on blood pumps, ventricular-assist devices and other permanent cardiovascular implants.

Modern mechanical valves no longer resemble the tall acrylic device Hufnagel placed in the descending aorta. Yet they retain its basic engineering insight: pressure can move a captive occluder to produce passive one-way flow. The historical progression came from improving where that mechanism could be implanted, how much it obstructed blood, what materials could survive inside the body and how its unavoidable risks could be managed.

Questions People Ask About Artificial Heart Valves

Who invented the first artificial heart valve?

Charles Hufnagel developed and implanted the first artificial valve used in a human in 1952. Because it was placed in the descending aorta rather than at the diseased natural valve, Albert Starr and M. Lowell Edwards are often credited with the first widely successful intracardiac mechanical valve.

When was the first successful mechanical mitral valve implanted?

Albert Starr implanted the Starr–Edwards caged-ball valve in the mitral position on September 21, 1960. The operation is recognized as the first long-term successful mitral replacement with that prosthesis.

Was the Starr–Edwards valve the first caged-ball valve?

No. Hufnagel’s 1952 prosthesis already used a captive ball. The Starr–Edwards design adapted the principle into a smaller valve that could be sewn into the heart at the mitral and, in later models, aortic or tricuspid position.

Why did caged-ball valves fall out of routine use?

The central ball obstructed forward flow, produced less favorable flow patterns and required a relatively bulky cage. Tilting-disc and bileaflet valves offered lower profiles and improved hemodynamics.

What are modern mechanical heart valves made from?

Many modern designs use pyrolytic carbon for the leaflets and blood-contacting housing, combined with a fabric sewing cuff and selected metallic or carbon-based structural components.

Can a mechanical valve work without electricity?

Yes. It is a passive pressure-operated device. Changes in pressure across the valve move its ball, disc or leaflets. No motor, battery or electronic controller is required.