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Tricuspid valve replacement
Tricuspid valve replacement A comparative experimental study with Starr-Edwards ball valve, Beall disc valve, and Kay-Shiley disc valve with muscle guard Complications after tricuspid valve replacement with the Starr-Edwards ball valve, Beall disc valve, and Kay-Shiley disc valve with a muscle guard were compared in 19 calves. The frustral areas were narrowed most significantly with the Starr-Edwards valve (5/ per cent) and the Beall valve (43 per cent); the least narrowing was found in the Kay-Shiley valve with a muscle guard (23 per cent). The narrowing of the area of the inflow orifice of the valve was less significant in all valves: 8, 20, and 6 per cent of the normal values, respectively. The mechanical impairment of excursion of the poppet due to the encroachment of muscle, scar tissue, thrombus, and encasement of the struts in the wall was the main cause of the reduction of the frustral area in Starr-Edwards and Beall valves. A second reason for the narrowing of the jrustral area of all three valves was neointimal overgrowth. This was the only reason for the reduction of the frustral area in the Kay-Shiley disc valve with the muscle guard. We concluded that the muscle guard was extremely effective in preserving an adequate frustral area in the experimental animal.
Tohru Mori, M.D., Soichiro Kitamura, M.D., Eduardo Verruno, M.D., Gabriel Kenaan, M.D., and Jerome Harold Kay, M.D., Los Angeles, Calif.
The hydraulic performance of currently used heart valve prostheses is good;' however, progressive postoperative stenosis of the implanted valve has been noted. Tissue ingrowth 2. 3 of the cloth covering narrows the valve placed in the mitral and tricuspid areas. Recent reports have stressed the progressive mechanical impairment of some valves.":" The purpose of this study was to compare the incidence of mechanical impairment of three prostheses, to compare the From the Thoracic and Cardiac Surgical Research Laboratory of the University of Southern California School of Medicine, Los Angeles, Calif. 90033. Supported by the Children's Heart Foundation of Southern California, the Los Angeles Thoracic and Cardiovascular Foundation, and the Los Angeles County Heart Association. Received for publication Jan. 11, 1974.
30
effect of this impairment of the valve areas of the prostheses, and finally to determine if a muscle guard' could prevent this postoperative stenosis of the prostheses. Method Tricuspid valve replacement was performed in 19 male Holstein-Friesian calves. The animals were 6 to 8 weeks old and weighed 59 to 72 kilograms. The implanted prostheses included Starr-Edwards ball valve size 4M, Models 6310 (4 calves) and 6320 (4 calves); Beall valve, medium size (3 calves) and large size (3 calves); and KayShiley valve, No. 8 with muscle guard (4 calves) and No. 9 with muscle guard (l calf) . The leaflets of the tricuspid valve were excised, but a small remnant was left around
Volume 68
Tricuspid valve replacement 3 1
Number 1 July, 1974
r -0.99
20
10
10
20
30 40 CALCULATED AREA
50(C~2J
-
Fig. 1. Regression line shows the relationship between the calculated area and the measured area.
the tricuspid annulus. The prosthesis was sutured to the annulus. * Two calves in the Beall valve group died within 1 week after operation and were omitted from the study. Four calves died within 118 days after operation and were subjected to further study. All other animals survived from 125 days to 300 days (average 278 days), at which time they were put to death. The heart was removed immediately. Evidence of verrucae was examined microscopically to exclude the presence of bacterial endocarditis. All hearts were examined particularly for the formation of thrombus, mobility of the poppets, and changes of the right ventricular wall. This included scar tissue formation on the ventricle, encasement of the struts in the wall, and neointimal ingrowth. The valve areas were analyzed as to two components: (1) the area of internal orifice • Disposable bubble oxygenators and Beall valves were donated by the Travenol Laboratories, Inc., Morton Grove, 111. The Kay-Shiley valves were donated by the Shiley Laboratories, Santa Ana, Calif. Starr-Edwards valves were purchased from the Edwards Laboratory,
Inc., Santa Ana, Calif.
of the flange and (2) the area between the flange and the poppet at maximum excursion of the poppet (the frustral area). 1. To measure the area of the internal orifice of the flange, a photograph was taken from the atrial side of the heart perpendicular to the plane of the flange. This photograph was treated as described below. 2. To measure the frustrum of the StarrEdwards ball valve, four photographs were taken of each heart from the right atrial side at a 45 degree angle to the plane of the flange in order to visualize the space demarcated by the ball, the flange, and the adjacent two struts. To measure the frustral area of the Beall and Kay-Shiley valves, four photographs were taken of each heart from the lateral sides of the valves, perpendicular to the plane that is surrounded by the adjacent two struts, the poppet, and the flange. The frustral area was obtained by adding all four areas . All photographs were enlarged by a projector to an optimal magnification on smooth paper, and the outlines of the areas were traced. Two tracings were made of each
The Journal of
32
Mori et al.
Thoracic and Cardiavascular Surgery
Table I. Valve areas measured in various types of valves Area of the internal orifice of the flange
Valve
Starr-Edwards Ball valve 4M, Model 6310
Ball valve 4M, Model 6320
Mean Beall Medium Large Kay-Shiley No.8 valve with muscle guard
Case No.
Control 169 186 195 194 196 197 198 Control 204 Control 210 Control 123 124 131 134
Mean No.9 valve with muscle guard
Frustral area
Per cent Per cent of COIlof COIlSize Size (sq. cm.] (sq. cm.) trol trol
Control 95
3.25 2.76 3.04 2.97 2.95 3.07 3.00 3.11 2.99 3.19 2.51 4.01 3.28 3.68 3.14 3.43 2.91 3.42 3.23 4.53 4.53
3.98 89 94 91 91 95 92 96 92 79 82 92 100 85 100 94 100
*
1.33 1.55 2.61 3.70 1.43 1.12 1.96 4.56 2.61 4.97 2.58 4.43 3.59 2.55 3.82 3.81 3.44 4.92 4.36
*
33 39 66 93 36 28 49
Excursion length
(mm.)
Per cent of COIltrol
11.0 2.0 4.5 5.0 6.0 11.0 5.0 3.0 5.2
18 41 45 55 100 45 27 47
Size
57 57 81 58 86 86 78 88
5.7 4.0 3.2 4.9 4.2 4.1 5.9 5.7
70 56 86 74 72 97
• In Case 169, the frustraI area was not measured due to thrombosis.
film, and each tracing was measured five times by a planimeter. The mean value of the area measured was corrected by the magnification rate to obtain the actual area. The valve areas thus obtained were compared to those of the control valves which were measured by the same method. To verify the accuracy of this method, photographs of the circles (the areas of which were calculated) were taken and treated as described above. The results are shown in Fig. 1. The accuracy was established to be close enough for the present study (correlation coefficient 0.99). Results Each prosthesis was considered to have two important areas which determine the effectiveness of the prosthesis in performing hydraulic work in vivo: the area of the internal orifice of the flange and the area of the frustrum. Table I shows the measured
valve areas of the three types of prostheses. Starr-Edwards ball valve. Eight calves with this type of valve were put to death 118 to 264 days (average 229 days) after operation. One calf had bacterial endocarditis and was omitted from this study. The in vivo area of the internal orifice of the flange ranged from 2.76 to 3.11 sq. em. (average 2.99 sq. em.) or from 89 to 96 per cent (average 92 per cent) of the control area. Thus, a sufficient amount of the inflow area was preserved, as compared to the control area. The frustral area ranged from 1.12 to 3.70 sq. em. (average 1.96 sq. cm.), which corresponded to from 28 to 93 per cent (average 49 per cent) of the control area. Therefore, this area was markedly reduced in vivo. The excursion length ranged from 2.0 to 11.0 mm. (average 5.2 mm.) or 18 to 100 per cent (average 47 per cent) of the control. Therefore, the reduction of the frustral area was mainly due to the re-
Volume 68 Number 1
Tricuspid valve replacement
33
July, 1974
197 Fig. 2A. Representative picture of the encasement of the struts of a Starr-Edwards valve in the right ventricle. Arrow indicates the large fibrin deposit on the strut.
Fig. 28. Thick neointimal overgrowth around the flange of a Starr-Edwards valve is shown. The arrows indicate the thick fibrin deposits on the struts which impeded the excursion of the poppet.
duction of the excursion length. Pathological observation revealed marked encasement of the struts in the right ventricular wall in 4 of 8 calves, as shown in Fig. 2A. Three hearts had a mass of scar tissue on the right ventricular wall. In 2 cases, this protrusion impaired the excursion of the poppets. The valve area was also reduced by neointimal overgrowth. The neointimal growth on the atrial side of the flange was smooth and thin. However, on the ventricular side of the inflow orifice, thick membranous neointima was formed and narrowed the frustral area. Fig. 2B shows this type of neointimal overgrowth. In this group, the frustral area was narrowed markedly due to encasement of the struts in the ventricular wall, protrusion of scar tissue which obstructed the excursion of the poppet, and, less significantly, due to the neointimalovergrowth. Beall disc valve. Beall valves were implanted in the tricuspid area of 6 calves. Three medium and three large valves were used. One calf from each group died early after the operation as a result of operative com-
plications and were omitted from this study. Another calf from each group died within 2 months after the operation. Autopsy in each animal revealed massive thrombus formation on the ventricular side of the prosthesis with complete obstruction of the orifice of each valve. Planimetric study was impossible in these cases. Two calves were put to death 232 and 230 days after operation. The area of the internal orifice of the flange was 2.51 sq. em. in a calf with a medium valve and 3.28 sq. em. in a calf with a large valve; these valves corresponded to 79 and 82 per cent of the control values, respectively. The frustral area was 2.61 sq. em. in the calf with a medium valve and 2.58 sq. em. in the calf with the large valve. Both measurements were 57 per cent of the control value. Both valves had small thrombi at the junctures of the struts to the flanges. These thrombi were large enough to impede the poppet's excursion. In each valve, excursion parallel to the plane of the flange was impossible, and eight semilunar notchings were observed around the edges of the poppet. In addition to the thrombus, trabeculae
34
Mori et al.
The Journal of Thoracic and Cardiovascular Surgery
95 Fig. 3. Encroachment of the muscle mass in a Beall valve. The mass impeded the excursion of the poppet. The arrows indicate the mu scle mass.
Fig . 4. Picture of representative heart showing the muscle guard in the right ventricle.
carneae of the right ventricle protruded into the confines of the poppet, thereby preventing smooth excursion of the poppet in one valve (Fig. 3). The excursion length could not be measured due to the irregularity of the protrusion. In this group , the reduction of the valve area was more marked in the frustral area, because the excursion of the poppet was impeded by thrombus or protrusion of the trabeculae carneae. Kay-Shiley disc valves. Kay-Shiley disc valves with a muscle guard were implanted into 5 animals. These were killed 283 to 300 days after operation. In 4 animals with a No.8 valve, the area of internal orifice of the flange ranged from 2.91 to 3.43 sq. em. (average 3.23 sq. cm.), 85 to 100 per cent (average 94 per cent) of the control value. The frustral area ranged from 2.55 to 3.82 sq. em. (average 3.44 sq. em.) or 58 to 86 per cent (average 78 per cent) of the control. The excursion lengths were 3.2 to 4.9 mm. (average 4.1 mm.) or 56 to 86 per cent of the control value (average 72 per cent).
In the No.9 valve, the area of the internal orifice of the flange was 4.53 sq. em., which corresponded to 100 per cent of the control value. The frustral area was 4.36 sq. em. (88 per cent of the control). The excursion length was 5.7 mm. (97 per cent of the control) . In 4 calves, thick neointima1 ridges surrounded the internal orifice of the valve on the ventricular side. These sleeve-like ridges tended to shorten the effective excursion length of the poppets. However, there was no impairment of mobility of the poppet. The muscle guard of all valves was attached to the right ventricular wall and was covered by a thin neointima (Fig. 4). Fig. 5 shows the over-all results of the postoperative reduction of the valve area. In each type of valve, the reduction was more marked for the frustral area than for the internal orifice of the flange. The reduction of the frustral area was most marked with the Starr-Edwards valve and least marked with the Kay-Shiley valve with a muscle guard .
Volume 68
Tricuspid valve replacement
Number 1
35
July, 1974
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STARR-EDWARD~
BEALL VALVE
%J 700
VALVE
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...;::
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20-
20
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A B TYPES of VALVE AREAS
A
B
Fig. 5. Schematic representation of the valve areas in ratio to the control areas. *, Large size. **, Medium size. ***, No.9 valve. A, Decrease in area of the internal orifice of the flange. B, Decrease in the frustral area.
Discussion
Alterations of the various types of artificial prostheses have improved the postoperative hemodynamic function of these valves and lowered the incidence of thromboembolic complications. 1, 8-12 These valves have been developed mainly for mitral and aortic valve replacement, but they have been used in the tricuspid area with little, if any, modification. The configuration of the inside of the right ventricle is significantly different from that of the left ventricle. Most significant is that the muscle completely surrounds the annulus of the tricuspid valve; on the other hand, with the mitral annulus, the aortic outflow area is positioned so as to prevent the left ventricular muscle from being in close contact with the mitral annulus over a significant area. With tricuspid valve replacement, the right ventricular muscle frequently impedes function of the poppet, with resultant thrombosis or stenosis. These problems are especially prevalent with caged ball valves,"- G, s, 10 Complications
have included encasement of the struts in the right ventricular wall and deposition of fibrin on the struts, which cause the poppet to stick. These complications were confirmed in our animal experiments. The complications not only occurred in calves with StarrEdwards ball valves, but also in those calves with Beall disc valves. The hearts used in these experiments were thought to be comparable to human hearts, weighing 350 to 380 grams. Postoperative narrowing of the StarrEdwards and Beall prostheses in the present experiment was caused by encroachment of thrombus, scar tissue, and muscle, which interfered with the excursion of the poppet. The neointimal overgrowth was a secondary problem adding to the narrowing. The muscle guard on the Kay-Shiley disc valve played an important role in preventing the encroachment of the right ventricle on the poppet in the tricuspid area. The muscle guard' was first introduced for mitral
36
Mori et
valve replacement in order to prevent the encroachment of the muscle of the ventricle at the mural area on the poppet and to allow insertion of a large valve in a small ventricle without the risk of the poppet sticking due to muscle encroachment. In the present experiment, it is apparent that the muscle guard is effective in preventing the mechanical impairment of the poppet by the right ventricular muscle. REFERENCES
2
3
4
5
The Journal of
at.
Winter, T. Q., Reis, R. L., Glancy, D. L., Robert, W. c., Epstein, S. E., and Morrow, A. G.: Current Status of the Starr-Edwards Cloth-Covered Prosthetic Cardiac Valves, Circulation 45: 14, 1972 (Suppl. I). Braunwald, N. S., and Morrow, A. G.: Tissue Ingrowth and the Rigid Heart Valve: Review of Clinical and Experimental Experience During the Past Year, J. THORAC. CARDIOVASC. SURG. 56: 307, 1968. Russell, T., II, Kremkau, E. L., Kloster, F., and Starr, A.: Late Hemodynamic Function of Cloth-Covered Starr-Edwards Valve Prostheses, Circulation 45: 8, 1972 (Suppl. I). Ibarra-Perez, C., Rodriguez-Trujillo, F., and Perez-Redondo, H.: Engagement of Ventricular Myocardium by Struts of Mitral Prosthesis, J. THoRAc. CARDIOVASC. SURG. 61: 403, 1971. Vander Veer, J. B., Rhyneer, G. S., Hodam,
Thoracic and Cardiovascular Surgery
6
7 8
9
10
11
12
R. P., and Kloster, F. E.: Obstruction of Tricuspid Ball-Valve Prostheses, Circulation 43: 62, 1971 (Suppl. I). Kalke, B., Korns, M. E., Goott, B., Lillehei, C. W., and Edwards, J. E.: Engagement of Ventricular Myocardium by Open-Cage Atrioventricular Valvular Prosthesis, J. THORAc. CARDIOVASC. SURG. 58: 92, 1969. Kay, J. H.: The Muscle Guard for Mitral Valve Prostheses, Arch. Surg. 98: 626, 1969. Duff, W. R., and Fox, R. W.: Prosthetic Cardiac Valves: An in Vitro Study, J. THORAC. CARDIOVASC. SURG. 63: 131, 1972. Beall, A. C., Jr., BloodweIl, R. D., Arbecast, N. R., Liotta, D., Cooley, D. A., and De Bakey, M. E.: Mitral Valve Replacement With Dacron-Covered Disc Prosthesis to Prevent Thromboembolism: Clinical Experience in 202 Patients, in Brewer, L. A., Ill, editor: Prosthetic Heart Valves, Springfield, Ill., 1969, Charles C Thomas, Publisher, p. 319. Reid, J. A., Stevens, T. W., Sigwart, D., Fulweber, R. C., and Alexander, J. K.: Hemodynamic Evaluation of the BeaIl Mitral Valve Prosthesis, Circulation 45: 7, 1972 (Suppl. I). Hodam, R., Starr, A., Herr, R., and Pierie, W. R.: Early Clinical Experience With ClothCovered Valvular Prostheses, Ann. Surg. 170: 471, 1969. Reis, R. L., Glancy, D. L., O'Brien, K., Epstein, S. E., and Morrow, A. G.: Clinical and Hemodynamic Assessments of Fabric-Covered Starr-Edwards Prosthetic Valves, J. THORAC. CARDIOVASC. SURG. 59: 84, 1970.
Tohru Mori, M.D., Soichiro Kitamura, M.D., Eduardo Verruno, M.D., Gabriel Kenaan, M.D., and Jerome Harold Kay, M.D., Los Angeles, Calif.
The hydraulic performance of currently used heart valve prostheses is good;' however, progressive postoperative stenosis of the implanted valve has been noted. Tissue ingrowth 2. 3 of the cloth covering narrows the valve placed in the mitral and tricuspid areas. Recent reports have stressed the progressive mechanical impairment of some valves.":" The purpose of this study was to compare the incidence of mechanical impairment of three prostheses, to compare the From the Thoracic and Cardiac Surgical Research Laboratory of the University of Southern California School of Medicine, Los Angeles, Calif. 90033. Supported by the Children's Heart Foundation of Southern California, the Los Angeles Thoracic and Cardiovascular Foundation, and the Los Angeles County Heart Association. Received for publication Jan. 11, 1974.
30
effect of this impairment of the valve areas of the prostheses, and finally to determine if a muscle guard' could prevent this postoperative stenosis of the prostheses. Method Tricuspid valve replacement was performed in 19 male Holstein-Friesian calves. The animals were 6 to 8 weeks old and weighed 59 to 72 kilograms. The implanted prostheses included Starr-Edwards ball valve size 4M, Models 6310 (4 calves) and 6320 (4 calves); Beall valve, medium size (3 calves) and large size (3 calves); and KayShiley valve, No. 8 with muscle guard (4 calves) and No. 9 with muscle guard (l calf) . The leaflets of the tricuspid valve were excised, but a small remnant was left around
Volume 68
Tricuspid valve replacement 3 1
Number 1 July, 1974
r -0.99
20
10
10
20
30 40 CALCULATED AREA
50(C~2J
-
Fig. 1. Regression line shows the relationship between the calculated area and the measured area.
the tricuspid annulus. The prosthesis was sutured to the annulus. * Two calves in the Beall valve group died within 1 week after operation and were omitted from the study. Four calves died within 118 days after operation and were subjected to further study. All other animals survived from 125 days to 300 days (average 278 days), at which time they were put to death. The heart was removed immediately. Evidence of verrucae was examined microscopically to exclude the presence of bacterial endocarditis. All hearts were examined particularly for the formation of thrombus, mobility of the poppets, and changes of the right ventricular wall. This included scar tissue formation on the ventricle, encasement of the struts in the wall, and neointimal ingrowth. The valve areas were analyzed as to two components: (1) the area of internal orifice • Disposable bubble oxygenators and Beall valves were donated by the Travenol Laboratories, Inc., Morton Grove, 111. The Kay-Shiley valves were donated by the Shiley Laboratories, Santa Ana, Calif. Starr-Edwards valves were purchased from the Edwards Laboratory,
Inc., Santa Ana, Calif.
of the flange and (2) the area between the flange and the poppet at maximum excursion of the poppet (the frustral area). 1. To measure the area of the internal orifice of the flange, a photograph was taken from the atrial side of the heart perpendicular to the plane of the flange. This photograph was treated as described below. 2. To measure the frustrum of the StarrEdwards ball valve, four photographs were taken of each heart from the right atrial side at a 45 degree angle to the plane of the flange in order to visualize the space demarcated by the ball, the flange, and the adjacent two struts. To measure the frustral area of the Beall and Kay-Shiley valves, four photographs were taken of each heart from the lateral sides of the valves, perpendicular to the plane that is surrounded by the adjacent two struts, the poppet, and the flange. The frustral area was obtained by adding all four areas . All photographs were enlarged by a projector to an optimal magnification on smooth paper, and the outlines of the areas were traced. Two tracings were made of each
The Journal of
32
Mori et al.
Thoracic and Cardiavascular Surgery
Table I. Valve areas measured in various types of valves Area of the internal orifice of the flange
Valve
Starr-Edwards Ball valve 4M, Model 6310
Ball valve 4M, Model 6320
Mean Beall Medium Large Kay-Shiley No.8 valve with muscle guard
Case No.
Control 169 186 195 194 196 197 198 Control 204 Control 210 Control 123 124 131 134
Mean No.9 valve with muscle guard
Frustral area
Per cent Per cent of COIlof COIlSize Size (sq. cm.] (sq. cm.) trol trol
Control 95
3.25 2.76 3.04 2.97 2.95 3.07 3.00 3.11 2.99 3.19 2.51 4.01 3.28 3.68 3.14 3.43 2.91 3.42 3.23 4.53 4.53
3.98 89 94 91 91 95 92 96 92 79 82 92 100 85 100 94 100
*
1.33 1.55 2.61 3.70 1.43 1.12 1.96 4.56 2.61 4.97 2.58 4.43 3.59 2.55 3.82 3.81 3.44 4.92 4.36
*
33 39 66 93 36 28 49
Excursion length
(mm.)
Per cent of COIltrol
11.0 2.0 4.5 5.0 6.0 11.0 5.0 3.0 5.2
18 41 45 55 100 45 27 47
Size
57 57 81 58 86 86 78 88
5.7 4.0 3.2 4.9 4.2 4.1 5.9 5.7
70 56 86 74 72 97
• In Case 169, the frustraI area was not measured due to thrombosis.
film, and each tracing was measured five times by a planimeter. The mean value of the area measured was corrected by the magnification rate to obtain the actual area. The valve areas thus obtained were compared to those of the control valves which were measured by the same method. To verify the accuracy of this method, photographs of the circles (the areas of which were calculated) were taken and treated as described above. The results are shown in Fig. 1. The accuracy was established to be close enough for the present study (correlation coefficient 0.99). Results Each prosthesis was considered to have two important areas which determine the effectiveness of the prosthesis in performing hydraulic work in vivo: the area of the internal orifice of the flange and the area of the frustrum. Table I shows the measured
valve areas of the three types of prostheses. Starr-Edwards ball valve. Eight calves with this type of valve were put to death 118 to 264 days (average 229 days) after operation. One calf had bacterial endocarditis and was omitted from this study. The in vivo area of the internal orifice of the flange ranged from 2.76 to 3.11 sq. em. (average 2.99 sq. em.) or from 89 to 96 per cent (average 92 per cent) of the control area. Thus, a sufficient amount of the inflow area was preserved, as compared to the control area. The frustral area ranged from 1.12 to 3.70 sq. em. (average 1.96 sq. cm.), which corresponded to from 28 to 93 per cent (average 49 per cent) of the control area. Therefore, this area was markedly reduced in vivo. The excursion length ranged from 2.0 to 11.0 mm. (average 5.2 mm.) or 18 to 100 per cent (average 47 per cent) of the control. Therefore, the reduction of the frustral area was mainly due to the re-
Volume 68 Number 1
Tricuspid valve replacement
33
July, 1974
197 Fig. 2A. Representative picture of the encasement of the struts of a Starr-Edwards valve in the right ventricle. Arrow indicates the large fibrin deposit on the strut.
Fig. 28. Thick neointimal overgrowth around the flange of a Starr-Edwards valve is shown. The arrows indicate the thick fibrin deposits on the struts which impeded the excursion of the poppet.
duction of the excursion length. Pathological observation revealed marked encasement of the struts in the right ventricular wall in 4 of 8 calves, as shown in Fig. 2A. Three hearts had a mass of scar tissue on the right ventricular wall. In 2 cases, this protrusion impaired the excursion of the poppets. The valve area was also reduced by neointimal overgrowth. The neointimal growth on the atrial side of the flange was smooth and thin. However, on the ventricular side of the inflow orifice, thick membranous neointima was formed and narrowed the frustral area. Fig. 2B shows this type of neointimal overgrowth. In this group, the frustral area was narrowed markedly due to encasement of the struts in the ventricular wall, protrusion of scar tissue which obstructed the excursion of the poppet, and, less significantly, due to the neointimalovergrowth. Beall disc valve. Beall valves were implanted in the tricuspid area of 6 calves. Three medium and three large valves were used. One calf from each group died early after the operation as a result of operative com-
plications and were omitted from this study. Another calf from each group died within 2 months after the operation. Autopsy in each animal revealed massive thrombus formation on the ventricular side of the prosthesis with complete obstruction of the orifice of each valve. Planimetric study was impossible in these cases. Two calves were put to death 232 and 230 days after operation. The area of the internal orifice of the flange was 2.51 sq. em. in a calf with a medium valve and 3.28 sq. em. in a calf with a large valve; these valves corresponded to 79 and 82 per cent of the control values, respectively. The frustral area was 2.61 sq. em. in the calf with a medium valve and 2.58 sq. em. in the calf with the large valve. Both measurements were 57 per cent of the control value. Both valves had small thrombi at the junctures of the struts to the flanges. These thrombi were large enough to impede the poppet's excursion. In each valve, excursion parallel to the plane of the flange was impossible, and eight semilunar notchings were observed around the edges of the poppet. In addition to the thrombus, trabeculae
34
Mori et al.
The Journal of Thoracic and Cardiovascular Surgery
95 Fig. 3. Encroachment of the muscle mass in a Beall valve. The mass impeded the excursion of the poppet. The arrows indicate the mu scle mass.
Fig . 4. Picture of representative heart showing the muscle guard in the right ventricle.
carneae of the right ventricle protruded into the confines of the poppet, thereby preventing smooth excursion of the poppet in one valve (Fig. 3). The excursion length could not be measured due to the irregularity of the protrusion. In this group , the reduction of the valve area was more marked in the frustral area, because the excursion of the poppet was impeded by thrombus or protrusion of the trabeculae carneae. Kay-Shiley disc valves. Kay-Shiley disc valves with a muscle guard were implanted into 5 animals. These were killed 283 to 300 days after operation. In 4 animals with a No.8 valve, the area of internal orifice of the flange ranged from 2.91 to 3.43 sq. em. (average 3.23 sq. cm.), 85 to 100 per cent (average 94 per cent) of the control value. The frustral area ranged from 2.55 to 3.82 sq. em. (average 3.44 sq. em.) or 58 to 86 per cent (average 78 per cent) of the control. The excursion lengths were 3.2 to 4.9 mm. (average 4.1 mm.) or 56 to 86 per cent of the control value (average 72 per cent).
In the No.9 valve, the area of the internal orifice of the flange was 4.53 sq. em., which corresponded to 100 per cent of the control value. The frustral area was 4.36 sq. em. (88 per cent of the control). The excursion length was 5.7 mm. (97 per cent of the control) . In 4 calves, thick neointima1 ridges surrounded the internal orifice of the valve on the ventricular side. These sleeve-like ridges tended to shorten the effective excursion length of the poppets. However, there was no impairment of mobility of the poppet. The muscle guard of all valves was attached to the right ventricular wall and was covered by a thin neointima (Fig. 4). Fig. 5 shows the over-all results of the postoperative reduction of the valve area. In each type of valve, the reduction was more marked for the frustral area than for the internal orifice of the flange. The reduction of the frustral area was most marked with the Starr-Edwards valve and least marked with the Kay-Shiley valve with a muscle guard .
Volume 68
Tricuspid valve replacement
Number 1
35
July, 1974
(%J 700
STARR-EDWARD~
BEALL VALVE
%J 700
VALVE
-.
...;::
;':;80
80
~
:lI
~
III
;'
:lI60
60
...
:..
.0
(%J 700
-.
KAY-SHILEY VALVE
80
60
0
:i!
"'40 I'l
40
40
20-
20
()
:t
:il
e...
20
A
B
A B TYPES of VALVE AREAS
A
B
Fig. 5. Schematic representation of the valve areas in ratio to the control areas. *, Large size. **, Medium size. ***, No.9 valve. A, Decrease in area of the internal orifice of the flange. B, Decrease in the frustral area.
Discussion
Alterations of the various types of artificial prostheses have improved the postoperative hemodynamic function of these valves and lowered the incidence of thromboembolic complications. 1, 8-12 These valves have been developed mainly for mitral and aortic valve replacement, but they have been used in the tricuspid area with little, if any, modification. The configuration of the inside of the right ventricle is significantly different from that of the left ventricle. Most significant is that the muscle completely surrounds the annulus of the tricuspid valve; on the other hand, with the mitral annulus, the aortic outflow area is positioned so as to prevent the left ventricular muscle from being in close contact with the mitral annulus over a significant area. With tricuspid valve replacement, the right ventricular muscle frequently impedes function of the poppet, with resultant thrombosis or stenosis. These problems are especially prevalent with caged ball valves,"- G, s, 10 Complications
have included encasement of the struts in the right ventricular wall and deposition of fibrin on the struts, which cause the poppet to stick. These complications were confirmed in our animal experiments. The complications not only occurred in calves with StarrEdwards ball valves, but also in those calves with Beall disc valves. The hearts used in these experiments were thought to be comparable to human hearts, weighing 350 to 380 grams. Postoperative narrowing of the StarrEdwards and Beall prostheses in the present experiment was caused by encroachment of thrombus, scar tissue, and muscle, which interfered with the excursion of the poppet. The neointimal overgrowth was a secondary problem adding to the narrowing. The muscle guard on the Kay-Shiley disc valve played an important role in preventing the encroachment of the right ventricle on the poppet in the tricuspid area. The muscle guard' was first introduced for mitral
36
Mori et
valve replacement in order to prevent the encroachment of the muscle of the ventricle at the mural area on the poppet and to allow insertion of a large valve in a small ventricle without the risk of the poppet sticking due to muscle encroachment. In the present experiment, it is apparent that the muscle guard is effective in preventing the mechanical impairment of the poppet by the right ventricular muscle. REFERENCES
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at.
Winter, T. Q., Reis, R. L., Glancy, D. L., Robert, W. c., Epstein, S. E., and Morrow, A. G.: Current Status of the Starr-Edwards Cloth-Covered Prosthetic Cardiac Valves, Circulation 45: 14, 1972 (Suppl. I). Braunwald, N. S., and Morrow, A. G.: Tissue Ingrowth and the Rigid Heart Valve: Review of Clinical and Experimental Experience During the Past Year, J. THORAC. CARDIOVASC. SURG. 56: 307, 1968. Russell, T., II, Kremkau, E. L., Kloster, F., and Starr, A.: Late Hemodynamic Function of Cloth-Covered Starr-Edwards Valve Prostheses, Circulation 45: 8, 1972 (Suppl. I). Ibarra-Perez, C., Rodriguez-Trujillo, F., and Perez-Redondo, H.: Engagement of Ventricular Myocardium by Struts of Mitral Prosthesis, J. THoRAc. CARDIOVASC. SURG. 61: 403, 1971. Vander Veer, J. B., Rhyneer, G. S., Hodam,
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R. P., and Kloster, F. E.: Obstruction of Tricuspid Ball-Valve Prostheses, Circulation 43: 62, 1971 (Suppl. I). Kalke, B., Korns, M. E., Goott, B., Lillehei, C. W., and Edwards, J. E.: Engagement of Ventricular Myocardium by Open-Cage Atrioventricular Valvular Prosthesis, J. THORAc. CARDIOVASC. SURG. 58: 92, 1969. Kay, J. H.: The Muscle Guard for Mitral Valve Prostheses, Arch. Surg. 98: 626, 1969. Duff, W. R., and Fox, R. W.: Prosthetic Cardiac Valves: An in Vitro Study, J. THORAC. CARDIOVASC. SURG. 63: 131, 1972. Beall, A. C., Jr., BloodweIl, R. D., Arbecast, N. R., Liotta, D., Cooley, D. A., and De Bakey, M. E.: Mitral Valve Replacement With Dacron-Covered Disc Prosthesis to Prevent Thromboembolism: Clinical Experience in 202 Patients, in Brewer, L. A., Ill, editor: Prosthetic Heart Valves, Springfield, Ill., 1969, Charles C Thomas, Publisher, p. 319. Reid, J. A., Stevens, T. W., Sigwart, D., Fulweber, R. C., and Alexander, J. K.: Hemodynamic Evaluation of the BeaIl Mitral Valve Prosthesis, Circulation 45: 7, 1972 (Suppl. I). Hodam, R., Starr, A., Herr, R., and Pierie, W. R.: Early Clinical Experience With ClothCovered Valvular Prostheses, Ann. Surg. 170: 471, 1969. Reis, R. L., Glancy, D. L., O'Brien, K., Epstein, S. E., and Morrow, A. G.: Clinical and Hemodynamic Assessments of Fabric-Covered Starr-Edwards Prosthetic Valves, J. THORAC. CARDIOVASC. SURG. 59: 84, 1970.