Health Sciences · Temerty Faculty of Medicine
A small (5.4 cm square) clear plastic case with a hinged lid contains the following:
A curved object composed of Dacron fabric with a flexible silicone coating is stored in a vacuum formed cradle within the clear case.
A piece of folded tissue paper with a white label affixed to one side.
Accession Number: 2020.med.6
Alternative Name: Mechanical Heart Valve (MHV)
Primary Materials: Dacron, Silicone
The white label reads as follows: “Hufnagel 1 1/2″ Leaflet Valve”
Case: Height = 3.3, Length = 5.3, Width = 5.3.
This is a prosthesis that replaces a single coronary cusp (also known as a leaflet). There are three such cusps in the aortic valve linking the heart to the coronary artery.
The prosthetic leaflet is “made of a terylene (Dacron) cloth into which silicone rubber is impregnated under high pressure and cured by heat.” (Hufnagel and Conrad 1961, 278). The lower (reflex) edge of the leaflet is a double layer of cloth that is left uncoated to promote the ingrowth of heart tissue. It also permitted the leaflet to be sutured into the aortic ring.
One or more of these leaflets were used to repair a damaged valve. The system was also available as a total valvular replacement, an integral three-cusp unit. This prosthesis was introduced in the early 1960s. The sophisticated heart surgery that it demanded was made possible by innovations such as cardiopulmonary bypass and cardioplegia.
Good: The curved object is adhering to its vacuum formed cradle. It was not removed for cataloguing purposes in order to avoid damaging it.
2020.med.8 is a similar valve of slightly smaller size.
Manufacturer:
Date of Manufacture: c. 1960s.
This artifact belongs to a small collection of items related to cardiac surgery that was collected by Dr. Wilfred Gordon “Bill” Bigelow (1913 – 2005). After his death, the collection was donated to the Cardiovascular Sciences Collaborative Program of the University of Toronto, where it is currently on display.
National Museum of American History, Behring Center. “Hufnagel Leaflet Valve, 2015.0031.09“. Catalogued Artifact.
Charles A. Hufnagel (1961). “The Direct Approach for the Correction of Aortic Insufficiency.” JAMA : The Journal of the American Medical Association 178, 3: 275.
Charles A. Hufnagel and Peter W. Conrad (1962). “Direct Repair of Dissecting Aneurysms of the Aorta.” Circulation 25, 3: 568–72.
William DeCesare, Charles Rath, and Charles Hufnagel (1965). “Hemolytic Anemia of Mechanical Origin with Aortic-Valve Prosthesis.” The New England Journal of Medicine (United States) 272, 20: 1045–50.
The introduction by Hufnagel and collaborators of the ball valve prosthesis in 1952 led to further research into the nature, and possible repair, of, heart conditions involving damage to the heart valves.
Towards the end of the 1950s, work began on a new prosthesis for direct repair of the aortic valve. By 1961, Hufnagel’s group introduced this leaflet prosthesis that replaced one or more of the cusps of the aortic valve.
The use of prosthetics within the heart was made possible by cardiopulmonary bypass and a technique called cardioplegia that was introduced in 1955 by Melrose et al in Durham. This involved cardiac arrest and the localized cooling of the myocardium. The heart was then opened, the aorta dissected from the pulmonary artery, and the damaged leaflet(s) removed and replaced.
Researchers soon noted that such cardiac prostheses caused hemolytic anemia, the destruction of red blood cells resulting from mechanical contact with features of the prosthesis. (See DeCesare, Rath and Hifnagel 1965). This issue continues into the present generation of cardiac prostheses.