Sewing Ring Research Articles

A new cardiac prosthesis: the St. Jude Medical cardiac valve: in vivo results.

The St. Jude Medical cardiac valve prosthesis is a low profile, lightweight, bi-leaflet, central-flow device constructed entirely of pyrolytic carbon. In vivo testing was performed in 24 cows in which the tricuspid valve (n = 14) or mitral valve (n = 10) was replaced by a St. Jude Medical prosthesis with a 26 mm tissue annulus diameter. Eight animals died in the operative period. The 16 surviving animals were sacrificed at 4, 8, 12, or 18 weeks. There were no valve-related deaths nor mechanical valve failures. Anticoagulation was not used in the postoperative period during which time monthly laboratory parameters were obtained including hemoglobin, hematocrit, white cell count, red cell count and indices, lactic acid dehydrogenase, serum haptoglobin, and, additionally at sacrifice, platelet and red cell morphology. Values indicated this prosthesis did not cause hemolysis. At sacrifice the pulmonary arterial tree and peripheral organs showed no evidence of thromboemboli. There was smooth endocardial ingrowth on all valve sewing rings. One valve had thrombus formation on the valve sewing ring. Nine animals were anesthetized prior to sacrifice and underwent open cardiac catheterization. Ventriculography (n = 6) showed minimal transvalvar reflux, and atriograms (n = 6) demonstrated central flow. Transvalvar gradients were 0 to 22 mm Hg (n = 9). One valve of an 18-week tricuspid implant was examined for wear; valve life was calculated to be greater than 2500 years. These data in conjunction with in vitro test results justify clinical trial of the St. Jude Medical prosthesis.

Non-cloth-covered caged-ball prostheses: The second decade

The Starr-Edwards Models 6120 mitral and 1200/60 aortic valves are caged-ball prostheses with cloth-covered sewing rings and bare-metal struts. Introduced in 1965, they have been in continuous clinical use longer than any other currently available heart valve prostheses. Late results with this valve are analyzed and compared with recent series employing other current valve prostheses. One hundred thirty-four mitral 6120 prostheses were inserted at the University of Oregon Health Sciences Center from 1965 through 1977, with 118 operative survivors followed for a mean of 5.4 years. Twelve-year survival rate (+/- standard error) was 50 (+/-8) percent. Twelve percent of late deaths were valve related. Eighty-eight (+/-5) percent of valves were still in place at 12 years. The embolic rate was 5.8 (+/-1.0) percent per patient-year for all emboli and 2.2(+/-0.6) percent per patient-year for serious emboli. Two hundred forty-nine operative survivors among 282 patients undergoing aortic valve replacement during the same period of time were followed for a mean of 4.3 years. Twelve-year survival was 61 (+/-6) percent and the removal-free rate was 92(+/-5) percent. Six percent of late deaths were valve related. Embolic rates were 5.0 (+/-.7) percent and 1.8 (+/-.4) percent per patient-year for all emboli and serius emboli, respectively. Structural failure, specifically ball variance, was not encountered with this prosthesis. Ninety percent of 10 year survivors are in N.Y.H.A. Functional Class I or II. There was one anticoagulant-related death in 1,698 patient-years of follow-up. The current non--cloth-covered caged-ball valves provide unquestionable durability and well-documented results into their second decade of use. They provide a base line for comparison with newer prostheses and offer a valid, current choice for both aortic and mitral valve replacement.

Fluid Stresses in the Vicinity of Disk, Ball, and Tilting Disk Prosthetic Heart Valves From In-Vitro Measurements

Experiments were conducted in a steady flow test apparatus with an axisymmetric aortic shaped test chamber using hot-wire anemometry to obtain local momentum transfer and turbulence data in the vicinity of the model disk, Kay-Shiley disk, Starr-Edwards ball and Bjork-Shiley tilting disk prosthetic heart valve configurations. These data for Reynolds numbers of 2000, 4000, and 6000 were used to locate regions of high stress where erythrocytes may be lysed or severely strained. Nondimensionalized velocity profiles downstream of the valves indicated a similarity of behavior for all Reynolds numbers at an axial location. Velocity gradients of magnitudes potentially damaging to erythrocytes were found. These gradients were largest for disk-type occluders. Large regions of separated flow were found to occur behind the valve sewing ring, distal to the valve occluder, and along the test chamber wall distal to the valve for all valves tested. Relatively high turbulence was found to exist distal to all valves tested. Turbulent stresses of magnitudes potentially hemolytic were measured.

Combined aortic and mitral valve replacement with the Björk-Shiley tilting disc valve prosthesis. Early and late results in 75 consecutive patients.

This study evaluates the early and late results of combined aortic and mitral valve replacement with the Björk-Shiley tilting disc valve prosthesis in 75 consecutive patients operated upon during a 6-year-period commencing October 1969. The Delrin disc model Björk-Shiley prosthesis was inserted in the first 20 patients and the pyrolytic carbon disc model in the remainder. The opening angle was increased from 50 degrees to 60 degress and the Teflon sewing ring was designed with two flanges in the pyrolytic carbon disc mitral model. The patient material was characterized by marked cardiomegaly, impaired physical working capacity, hypokinetic central circulation, pulmonary hypertension and a 59% incidence of atrial arrhythmias before operation. Surgery was performed during generalized hypothermia to 30 degrees C and selective coronary perfusion, and the mitral valve was always replaced first. There were no intra-operative deaths, although 7/75 patients (9%) died while in hospital. Twelve patients (16%) died in average 19 (2-59) months postoperatively. Thrombo-embolic complications, which were frequently associated with poor anticoagulation, occurred in 9 patients and were fatal in 4 cases, corresponding to an incidence per patient month of 0.005 and 0.002, respecitvely. This risk was not affected by the type of prosthesis. One patient required operative repair of an aortic paraprosthetic leakage. Clinical improvement was found in 88% of the long-term survivors. The maximal working capacity increased in average 41% over the pre-operative value (p less than 0.001) and cardiac enlargement diminished in average by 22% (p less than 0.001). The incidence of atrial arrhythmias decreased slightly to 48%. Haemolysis was mild and without clinical significance. The actuarial curve indicated a 75% survival rate 3 years after operation.

Complications of cloth-covered prosthetic valves: Results with a new mitral prosthesis

During a 12 year period 5,103 cardiac prosthetic valves in 4,193 patients have been evaluated for performance and incidence of complications. As a result of our experience, the advantages of fewer embolic phenomena, associated with epithelialization in completely cloth-covered valves and those with cloth-covered seating rings, are outweighed by the problems of cloth wear, hemolysis, and hemodynamic obstruction from tissue overgrowth. A valve has been designed which incorporates the desirable features of full-flow orifice, low-profile, self-washing principle, polished contact surfaces, durable materials, and a large eccentric sewing ring into a new mitral prosthesis. Clinical evaluation in 394 patients from Aug. 1, 1971, through Dec. 31, 1973, has demonstrated excellent hemodynamic function and a low incidence of thromboembolic phenomenon.

A hinged prosthetic cardiac valve fabricated of rigid components: Experimental evaluations in vitro and in vivo

Summary A prosthetic cardiac valve was designed that consisted of an annular valve body and a disc that pivoted about an eccentric hinge mechanism. The valve was compact and durable. The pressure gradient across the valve was approximately half of that associated with a ball valve of comparable diameter. Visualization of the flow patterns showed that flow through the major orifice was laminar, while that through the minor orifice was turbulent. The valve was implanted in the tricuspid position in 9 calves. Tissue growth around the valve body was a major problem in the first group of animals, but anticoagulation, hinge modification, and the use of a standard Starr-Edwards mitral sewing ring improved results in later implantations.

Elimination of sewing ring-metal seat interface in mitral valve prostheses.

In an effort to decrease the incidence of thromboembolic phenomena associated with prosthetic replacement of the mitral valve and to eliminate problems associated with swelling of moving parts employed in cardiac valve prostheses, a new mitral Teflon disc valve made of titanium was designed. The cage legs are covered with Teflon to reduce wear, and the entire sewing ring and base are covered with Dacron velour to encourage rapid tissue encapsulation. After accelerated fatigue testing and animal investigations, preliminary results in a clinical series of 73 patients appear most encouraging. Further time must pass, however, before statistically valid conclusions can be reached.

Sewing ring healing of cardiac valve prostheses.

A study of the healing of fabric sewing rings of cardiac valve prostheses is essentially a study of the replacement of thrombus by fibrous tissue, and the ultimate fate of the resultant scar. Our observations are drawn from personal studies of the healing of 48 different types of valve replacements in 300 calves and dogs over the past six and one-half years. None of the experimental animals received anticoagulant therapy postoperatively. The studies have included 7 different types of Starr-Edwards ball valves; 4 types of guided disc valves, and 4 types of guided flow ball valves of our own design, which incorporate the concept of the hidden sewing ring; ball valves constructed of 17 different alloys* with similar sewing rings; Hufnagel discoid valves; Gott hinged-leaflet valves; and many types of tissue and prosthetic leaflet or cusp valves. Pertinent factors governing the healing of the sewing rings of prosthetic valves have been observed. Correlation can be drawn between these factors and the healing of