The Angell-Shiley porcine xenograft.

A 4-year clinical experience with fresh allograft tissue valves prompted a trial of 0.5% buffered glutaraldehyde as a valve fixative and sterilant. Tanned allograft and porcine xenograft valves were inserted into experimental animals, and, beginning in 1970, similar valves were implanted in a series of patients now totaling 312. The clinical results are excellent. The 5-year valve-related mortality is 6% for patients who had mitral valve replacement and 16% for those with aortic valve replacement. To date, the incidence of thromboembolism is 1.3% per patient-year, and valve-related morbidity and mortality for the combined groups is 27.4%. Valve stent design has evolved from symmetrically configured metal to anatomically molded plastic. The maintenance of natural valve configuration has optimized leaflet coaptation and support, decreased tissue stress, and eliminated valve-stent dehiscence and tissue rupture seen in valves deformed to fit symmetrical stents. Stent design, controlled glutaraldehyde solutions, and fixation techniques have improved leaflet flexibility and reduced valve orifice to annulus diameter ratios, thus producing transvalvular gradients comparable to both mechanical and modified orifice tissue valves. To date, tissue failure, observed in only 1.0% (3 of 287) of patients, is the result of calcification (2 patients) and cusp rupture due to incomplete fixation (1 patient).

The saphenous vein versus internal mammary artery as a coronary bypass graft.

Controversy persists as regards the efficacy of aortocoronary saphenous vein bypass graft (SVBG) compared to direct internal mammary artery (IMA) anastomosis. In general, the IMA graft (IMAG) is considered to be superior as regards postoperative patency. To avoid preselection bias, 74 consecutive, unselected patients with bypassable lesions of the left anterior descending artery (LAD) were randomized to undergo either SVBG or IMAG to the LAD in 1972-1974. The majority of patients had, in addition, SVBGs to other vessels. Postoperative angiograms, an average of 6 months after surgery, were obtained in two-thirds of the patients. The following observations were made: (formula: see text). In this series there is no clear advantage of the IMAG over the SVBG. The preparation of the internal mammary artery for grafting is tedious and the anastomosis more difficult to perform. The resultant flow in the internal mammary artery graft is less overall than in the SVBG. In over 400 unselected SVBGs to the LAD that have been restudied thus far in our practice, an 86% patency rate has been achieved.

Section of tissue or prosthetic valve. A five-year prospective, randomized comparison.

After considerable experience, controversy persists between the selection of a tissue or prosthetic valve. In order to provide a nonbiased comparison, we designed a prospective, randomized study in September of 1970. Ninety-nine consecutive patients with isolated primary single valve replacement were randomized to tissue or prosthetic valves. The Tissue Bank supplied homografts which were either mounted for mitral replacement or used as free grafts for patients with small aortic roots. Starr-Edwards clot-covered prostheses were used for comparison. There was an even distribution of patients by age, sex, valve lesion, and New York Heart Classification attesting to the accuracy of the random selection. Anticoagulants were used in 33 patients who had operative or embolic evidence of atrial cloth or else history of thromboembolism. Thirty-five patients have undergone postoperative catheterization. Causes of death and valve failure are presented on an actuarial basis. Death in the Starr-Edwards patient group was sudden or due to fabric wear with subsequent thromboembolism, hemorrhage, or infection. We conclude that the tissue valve is a better choice for valve replacement. While there is no significant functional or hemodynamic apparent difference between the tissue and prosthetic valve, there is improvement in patient morbidity and mortality rate with the use of homografts, particularly in the aortic position. The primary cause of complications in the homograft is tissue deterioration, and this problem has been markedly reduced with advent of glutaraldehyde fixation. No such advance in solving the problem of host incompatability with the prosthesis has been forthcoming.