Evaluation of the 21 Mm Björk-Shiley Tilting Disc Valve in Patients with Narrow Aortic Roots: A Clinical, Haemodynamic and Angiographic Study

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Abstract
Nineteen out of 23 consecutive patients with aortic valvular lesions and narrow aortic roots, operated upon with the 21 mm Björk-Shiley tilting disc valve prosthesis, were subjected to a clinical and haemodynamic pre- and postoperative study. An angiographic examination was carried out after valve replacement. The total mortality was 1/23 patients (4%). Clinical improvement was found in 17/19 patients (89%) after surgery. No thrombo-embolic episodes occurred during the follow-up period. The main response to aortic valve replacement was an obvious reduction of the pressure load of the left ventricle as indicated by the marked decreases in left ventricular systolic pressure and stroke work. These changes were most pronounced at rest and accompanied by reduction of distressing symptoms, increase in working capacity and decrease in cardiac enlargement. Unloading of the left ventricle after aortic valve replacement did not influence heart rate, heart rhythm, stroke volume and kinetics of the central circulation to any major extent. The left ventricular end-diastolic pressure descreased slightly although not significantly and remained in average elevated after valve replacement. Pathologically elevated right ventricular systolic, pulmonary artery mean, and left atrial mean pressures before operation decreased to normal levels only at rest postoperatively. Similar changes were found for the pulmonary vascular resistance. Postoperative thoracic aortography demonstrated no significant aortic regurgitation in the 18 patients examined. Postoperative left ventricular angiograms revealed a sub-valvular muscular obstruction already demonstrable before surgery in 1/7 patients. The 21 mm Björk-Shiley tilting disc valve, with its high orifice to tissue diameter ratio, satisfactory pressure-flow characteristics and flat profile, demonstrates definite advantages in the surgical management of the narrow aortic root. The mean systolic pressure difference across this valve was 21.5 mmHg at rest, rising almost linearly with increasing aortic mean valve flow. According to its in vivo rheology, the 21 mm Björk-Shiley tilting disc valve seems to approach the criteria of an adequate substitute for aortic valvular lesions in patients with narrow aortic roots.

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