The usefulness of heart-lung machines, synthetic vascular grafts, and other cardiovascular replacement or support devices is undisputed, but they share a common disadvantage: Thrombi may form on the artificial surfaces, interfering with the device itself or eventually lodging in one of the patient's organs.
The problems begin, says Edwin W. Salzman, MD, professor of surgery at Harvard Medical School and Beth Israel Hospital, Boston, when "certain proteins carried in the plasma—fibrinogen is one of the most important—are selectively deposited on a surface in a thin coat.
"It is this thin film of protein," he told a recent American Heart Association seminar, "not the surface of the artificial material, that influences other blood proteins and platelets to find the surface attractive or unattractive and thus thrombogenic or thromboresistant."
There are two possible ways to cope with this, and Salzman's group is studying both. One is to develop artificial surfaces that are