Metallurgic and Design Development in Response to Mechanical Dysfunction of Björk-Shiley Heart Valves

Abstract

In 16 years' experience with the Björk-Shiley tilting disc valve, the failures encountered have been disc-related.

A. Obstruction of the disc movement in the aortic area has been due to faulty implantation technique, i.e. a suture cut too long and caught between the disc and the valve ring. Immediate reexploration, with cutting of the suture, has restored function. Disc obstruction in the mitral area has also been attributable to technique—leaving chordae tendineae too long. The author utilizes the universal sewing ring, which prevents the suture from encroaching on the disc.

B. Disc escape by strut dislocation or strut fracture is a risk which can be reduced by care during valve implantation, always using only the valve holder to orient the valve. Forceful use of forceps, or use of the disc itself as a handle, may produce a crack in the weld which can propagate a strut fracture in the course of a year. When a patient's condition suddenly deteriorates, with dyspnea and tachycardia, immediate referral to the heart surgeon can be life-saving. Stethoscopy and chest X-ray suffice to reveal disc location and/or outflow strut fracture. Other investigations waste crucial time, as only reoperation with ex-change of the valve can save the patient. To strengthen the valve and avoid a weld, a mono-outflow strut has now been used for three years at the Karolinska Hospital, with no mechanical dysfunction and with excellent hemodynamic results.