Hemodynamic evaluation of the Angell-Shiley porcine xenograft

J THORAC

CARDIOVASC SURG

84:297-305, 1982

Hemodynamic evaluation of the Angell-Shiley porcine xenograft The Angell-Shiley porcine xenograft was evaluated in 48 asymptomatic subjects who underwent cardiac catheterization an average of 14 months after operation. Nineteen patients had mitral and 29 had aortic valve replacement. The average mitral valve gradient was 8 :t 3 mm Hg and the average effective orifice area was 1.8 :t 0.6 em". The average aortic valve gradient was 22 :t 7 mm Hg and the average effective orifice area was 1.2 :t 0.3 em". During supine leg exercise, the average mitral valve gradient increased to 12 :t 4 mm Hg (p < 0.001) and the average aortic valve gradient increased to 27 :t 8 mm Hg (p < 0.001) compared to findings at rest. On the basis of data obtained with a regression analysis model, there is a high probability that an Angell-Shiley aortic xenograft with a stent diameter less than 25 mm will have a postoperative effective orifice area of less than 1 em", and that an Angell-Shiley mitral xenograft with a stent diameter less than 30 mm will have a postoperative effective orifice area of less than 1.5 em". Our data suggest that the Angell-Shiley xenograft has suboptimal hemodynamic performance in stent sizes less than 30 mm in the mitral position and less than 25 mm in the aortic position.

Juan Luis Delean, M.D., Madrid, Spain, Bernard R. Chaitman, M.D., Montreal, Quebec, Canada, Lorenzo Lopez-Bescos, M.D., Raoul Bonan, M.D., David Garcia-Dorado, M.D., and Ramiro Rivera, M.D., Madrid, Spain

T

he glutaraldehyde-fixed porcine xenograft is an acceptable valve substitute with an extensive clinical experience.tt'' Several hemodynamic studies have shown that the porcine xenograft is moderately obstructive in the smaller stent sizes.P: 14~16, 21-23 The degree of obstruction may differ according to stent design and tissue mounting procedure. I. 2, 21. 24 The Angell-Shiley xenograft conserves the original geometry of the porcine aortic valve in order to enhance durability and better distribute mechanical stress." 25 However, the unmodified right coronary cusp and interventricular septal shelf narrow the inside stent diameter, which may be a potential hemodynamic problem. The aim of this study is to examine the postoperative hemodynamic performance of the aortic and mitral AngellShiley bioprostheses at rest and during exercise.

Material and methods

Address for reprints: Juan Luis Delcan, M.D" Hospital Provincial de Madrid, Dr, Esquerdo, 46, Madrid, Spain.

Valve design. The Angell-Shiley porcine xenograft is obtained from a healthy porcine aortic root and trimmed to allow for a thin right coronary muscular cusp. The xenograft is fixed in 0.5% glutaraldehyde and mounted in one of 70 different anatomic stent configurations obtained from precise castings of actual porcine aortic roots. The base and struts are covered with Dacron cloth. The design of the flexible, anatomically configured stent assures natural leaflet coaptation and supports and reduces abnormal leaflet stress. The reconfiguration of the porcine aortic valve produces some compromise of the inflow orifice owing to the anatomic orientation of the right coronary cusp. Patient population. Between January, 1977, and December, 1977, 318 patients received Angell-Shiley xenografts at the Hospital Provincial de Madrid. After a mean follow-up of 18 months, 83% of the patients who had an aortic valve replacement, 56% of the patients who had a mitral valve replacement, and 62% of those who had multiple valve replacements were asymptomatic. Forty-eight asymptomatic patients who had no clinical evidence of valve dysfunction were selected to undergo a postoperative cardiac catheterization. Informed consent was obtained from all patients and no compli-

© 1982 The C. V. Mosby Co.

297

From the Cardiovascular Surgical and Hemodynamic Service, Hospital Provincial de Madrid, Madrid, Spain, and the Department of Medicine, Montreal Heart Institute, Montreal, Quebec, Canada. This study was supported in part through a scientific exchange program between Madrid and Quebec. Received for publication Sept. 15, 1981. Accepted for publication Nov. 24, 1981.

0022-5223/82/080297+09$00.9010

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298 Delcan et al.

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Table I. Clinical and hemodynamic data for patients with an Angell-Shiley mitral xenograft External Case No. (age, sex)

M-I (51, M-2 (35, M-3 (35, M-4 (43, M-5 (46, M-6 (32, M-7 (33, M-8 (31, M-9 (32, M-1O (40, M-1I (39, M-12 (38, M-13 (36, M-14 (39, M-15 (29, M-16 (42, M-17 (54, M-18 (67, M-19 (45, Totals

Predominant valvular lesion

MI F) MS F) MS M) MS M) MS-MI F) MS F) MS-MI M) MI F) MS-MI M) MS F) MS-MI F) MS M) MI F) MS F) MS M) MS M) MS F) MS M) MI F)

Status Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise

Postop . time (mo)

diameter (mm)

BSA (m 2 )

22

25

1.39

11

29

1.39

17

29

1.82

22

29

1.79

8

30

1.71

11

30

1.65

23

30

1.61

6

30

1.53

8

30

1.49

9

30

1.67

8

30

1.69

18

30

1.85

20

30

1.37

12

30

1.65

21

31

1.80

7

31

2.00

16

31

1.56

II

31

1.73

8

32

1.76

stent

Cardiac output (Llmin)

2.8 5.5 3.4 5.4 4 6 2.4 3.1 2.3 3.8 5.8 7.8 4.4 7.1 3.1 5.2 2.2 4 3.2 6.5 6.6 8.5 4.7 7.5 3.9 6.2 5.1 8.7 4.3 8.0 8.3 13.4 2.5 5.2 5.7 7.8 3.7 5.7 4.0 ± 1.5 6.6 ± 2.2

Legend: BSA, Body surface area. PA, Pulmonary artery. LA, Left atrium. LV, Left ventricle. MV, Mitral valve. MI, Mitral insufficiency. MS, Mitral stenosis.

cations occurred as the result of the catheterization procedure. The population contained 17 women and 31 men aged 22 to 67 years. The hemodynamic evaluation was performed an average of 14 (from 6 to 27) months after the operation. Of the 29 patients who had aortic valve replacement, 16 had predominant aortic regurgitation, two aortic stenosis, and 11 had mixed aortic valve disease (Table I). Of the 19 patients who had mitral valve replacement,

four had predominant mitral regurgitation, II had mitral stenosis, and four had mixed mitral valve disease (Table II). The average postoperative ejection fraction, calculated by the area-length method;" was 0.45 or greater in all but two patients (M-4 and A-25). Cardiac catheterization. Postoperative hemodynamic studies were carried out with patients in the fasting state after light sedation with oral diazepam. Right and left heart catheterizations were done by means of

Volume 84 Number 2 August, 1982

Angell-Shiley xenograft

299

Pressures (mm Hg) Hearl rate (beals /min)

110 150 60 80 98 140 58 110 80 120 106 120 104 110 80 180 86 130 64 90 80 120 74 100 74 110 108 170 79 105 80 140 60 110 60 115 74 120

PA (mean)

55/25 65/30 40/20 45/20 35/17 40/15 40/20 70/35 55/20 60/25 50/20 60/23

(40) (47) (30) (30) (27) (28) (27) (50) (40) (45) (33) (44)

40120 (30)

60/30 40/17 55/20 22/10 30/10 45/20 50/20 42/20 65/25 50/24 60/30 35/18 43/16

(45) (32) (40) (14) (20) (33) (40) (34) (45) (40) (45) (27) (27)

50123 (35)

50/23 (40) 40/13 (25) 55120 (40)

50/20 (30) 60120 (40)

35/14 40/15 30/13 35/18 30/15 40/20

(24) (30) (20) (23) (22) (30)

Mean LA

30 43 8 20 22 36 18 35 21 26 20 28 25 38 23 23 10 22 15 22 20 25 28 30 20 23 26 36 26 30 21 30 20 25 12 17 16 29

LV

Aorta

150/9 160/12 130/6 11017 90/3 140/12 90/15 120/21 130/14

150/90 160/90 130/80 110/60 90/60 140/90 90/50 120/80

110120

110170 120170

120/6

130175

12017

120170

120/17 100/20 130/14 140/15 98/12 113/10 130/14 140/16 130/9 135/14 130/13 140/13 130/12 150/12 120/6 130/15 140/15 160/16 120/12 150/10 130/17 150/12 100/10 100/11 100/10 130/16

120/80 140/90 130/84 140/80

81 ± 16 120 ± 20

standard and transseptal catheterization techniques. Direct transvalvular gradients were obtained across the aortic bioprosthesis by simultaneous recording of central aortic and left ventricular pressures. Mean gradients were determined by hand planimetry of 5 systolic cycles. Gradients across the mitral bioprosthesis were measured by a simultaneous recording of direct left atrial and left ventricular pressures, and the mean gradients were determined by hand planimetry of 5 di-

98170

113/80 130/80 140/80 130/80 135/85 130/80 140/85 130/84 150174 120175

130/80 130170

130/60 120/80 150172 130170

150/80 100/75 100170

100/80 130/84

MV gradient (mm Hg)

15 19 6 9 10 11 8 15 4 9 10 18

MVarea (em")

10 5 9 6 10 10 10 12 12 7 13 6 10 10 17 9 13 5 6 5 9 5 8

0.85 2.4 1.39 1.70 1.63 2.4 0.74 0.75 1.48 1.57 2 2.23 1.85 2.36 1.67 1.43 1.45 1.65 1.39 2.26 2.72 2.85 1.62 2.15 1.41 1.74 2.92 4.07 1.52 2.23 2.57 3.13 1.98 1.87 3.18 3.19 1.86 1.89

8 ± 3 12 ± 4

1.87 ± 0.6 2.20 ± 0.7

II

15 II

Regurgitation

1+

1+

astolic cycles. Cardiac output was measured by the indicator-dilution technique. Indocyanine green was injected into the main pulmonary artery and sampled from the central aorta. Valve orifice areas were calculated from the Gorlin and Gorlin'" formula using mean gradients and a constant of 31 for mitral and 44.5 for aortic valve determinations. All data were obtained at rest and during moderate supine leg exercise against 50 watts of resistance for 10 to 15 minutes.

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300 Delcan et al.

Thoracic and Cardiovascular Surgery

Table II. Clinical and hemodynamic data for patients with an Angell-Shiley aortic xenograft

Case No. (age, sex)

A-I (54, A-2 (50, A-3 (50, A-4 (44, A-5 (58, A-6 (49, A-7 (33, A-8 (18, A-9 (35, A-IO (55, A-II (35, A-12 (47, A-13 (51, A-14 (30, A-15 (39,

Predominant valvular lesion

AR-MS F) AR M) AR-AS M) AS-AR M) AR-AS F) AR F)

AS-AR M) AR F) AR F) AR M) AR M) AR M) AR M) AR M) AR M)

Status

Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise

Postop. time (mo)

External stent diameter (mm)

(m"}

27

23

1.65

18

23

1.69

6

25

1.80

8

25

1.90

13

26

1.74

25

26

1.54

6

26

1.59

6

26

1.56

15

26

1.60

22

27

1.98

18

27

1.95

BSA

19

27

1.82

26

27

1.61

8

27

2.03

8

28

1.85

Pressures (mm Hg)

Cardiac output (Llmm}

Heart rate (beats/min)

LV

4.1 7.5 4.1 10.4 3.9 6.3 5.6 7 3.6 5.2 3.1 5.5 5.5 6.4 6.1 11.7 4.6 5.4 3.7 5.9 5.6 10.2 4 6.3 4.3 6.3 7.3 10 7.5 11.4

129 136 82 155 72 72 69 89 69 94 80 94 100 120 80 120 135 164 66 103 69 116 87 129 80 150 101 120 80 120

206/10 220/16 164/18 220/13 170/14 280/30 170/10 184/20 100/12 132/15 130/10 168/13 140/9 160/9 128/5 200/8 160/12 200/20 160/22 188/20 127/12 201116 135/13 184/20 137/12 193/14 184/18 228/24 136/6 230/12

I

Aorta

188/136 196/140 130/80 168/88 150/90 240/130 133/80 144/84 90/64 106/66 110170 144/100 100/66 120/72 104/66 169/96 138/92 180/112 140/83 160/80 95170

156/90 120/90 152/100 116170 152/80 146/100 188/112 110/60 204/108

AV gradient (mm Hg)

AV area (em 2)

18 16 34 38 19 37 36 37 23 21 19 23 27 31 19 33 24 24 19 25 24 38 16 27 23 31 31 34 23 32

0.85 1.63 0.69 1.51 1.08 1.16 0.97 1.16 1.17 1.30 0.84 1.24 1.44 1.62 2 2.55 0.79 0.90 1.02 1.07 1.17 1.40 1.19 1.40 0.98 1.07 1.11 1.39 2.24 2.36

Regurgitation

1+ 1+

Legend: BSA, Body surface area. LV, Left ventricle. AV, Aortic valve. AR, Aortic regurgitation. MS, Mitral stenosis. AS, Aortic stenosis.

Uniplane left ventricular cineangiograms were obtained in the 30 degree right and 45 degree left anterior oblique positions. Patients with an aortic valve bioprosthesis also had a supravalvular contrast injection in the 45 degree left anterior oblique view to evaluate valve incompetence. Statistical analysis. The relationship between effective orifice area and external diameter of the xenograft was evaluated by means of a regression analysis for patients with an aortic or mitral valve xenograft. A similar analysis was performed by means of a linear and parabolic model'" to compare the calculated effective orifice area with (1) the total area of the xenograft and (2) the total radius of the bioprosthesis. The log effective orifice area was also compared to the log radius of the known stent size by means of a linear model. The best correlation was found between the

calculated effective orifice area and the stent diameter by means of a linear regression model. Significant differences among the measured parameters obtained from the linear regression equations were determined by analysis of variance. The 95% confidence limits for predicted effective orifice area from the manufacturer's stated stent size were calculated. Hemodynamic changes from rest to exercise were evaluated by a paired Student's t test.

Results Catheterization data at rest. The hemodynamic data for the 48 patients are shown in Tables I and II. The average mitral valve gradient was 8 ± 3 mm Hg (range 3 to IS) and the average effective orifice area was 1.8 ± 0.6 ern" (range 0.7 to 3.2). The average aortic valve gradient was 22 ± 7 mm Hg (range 10

Volume84 Number 2 August, 1982

Angell-Shiley xenograft

30 1

Table n.-Cont'd.

Case No. (age, sex) A-16 (40, M) A-17 (23, M) A-18

Predominant valvular lesion

AR AR AR

(27, F)

A-19 (49, M) A-20 (39, M) A-21 (40, M) A-22

AS-AR AS AS AR-MS

(22, M)

A-23 (52, A-24 (31, A-25 (49, A-26 (30, A-27 (31, A-28 (32, A-29 (45,

AS-AR

M)

AR M)

AS-AR M)

AR M)

AR M)

AR M)

AR M)

Status Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise Postop. Exercise

External stent diameter (mm)

BSA (m")

8

28

1.75

22

28

1.76

9

28

1.63

26

28

1.98

16

28

1.69

8

29

1.93

II

29

1.82

10

29

1.65

9

29

1.75

13

29

1.72

II

29

1.67

10

29

1.88

6

30

1.77

6

30

1.79

Postop. time (mo)

to 36) and the average effective orifice area was 1.2 ± 0.3 ern" (range 0.7 to 2.2). The correlation between the effective orifice area and the stent diameter of the mitral xenograft was significant (p = 0.022) and was defined by the equation: y = -5.351 + 0.479x (x = stent radius in mm, y = effective orifice area) (Fig. 1). The correlation between the effective orifice area and stent diameter of the aortic xenograft was also significant (p < 0.05) and was defined by the equation: y = -0.763 + 0.149x (Fig. 2). The random probability for the differences among the parameters from the linear regression equations was p = 0.078 for both groups. The slope of the linear expression was not the same for aortic and mitral xenografts over a similar range of stent sizes. Thus the effective orifice area for an individual stent size may vary depending on the pressure-flow characteristics of the implant position. Catheterization data with exercise. In patients with a mitral xenograft, the average heart rate response in-

Pressures (mm Hg)

Cardiac output (Llmm)

Heart rate (beats/min)

LV

4.2 6.2 6.1 10.7 5.8 8 7 9.7 4.9 7.0 6.5 9.6 3.8 7.7 3.5 6.6 4.6 6.4 4.2 5.7 4.0 9.6 5.0 9.5 5 7 5.2 8.2

126 140 86 140 115 151 116 137 72 88 60 80 84 114 74 104 129 130 56 100 64 108 66 102 95 138 100 130

140/12 150/16 140/8 184/12 13018 150/10 183/15 236/20 160/13 206/24 130/8 169114 164/16 178/16 116/13 180/24 146/12 154/13 130/12 150/13 11117 167/16 169/12 210/20 140/8 180/9 134/13 160/20

I Aorta 120/86 117/72 110/80 140/92 110/80 120/80 140/80 188/110 130/90 1721108 94/60 120/72 156/100 1601130 104170 160/90 128/100 140/100 105170 130170 98/66 142/90 144/80 184/100 126/86 164197 112176 138/80

AV gradient (mm Hg)

AV area (em")

14 32 23 31 12 12 32 38 26 29 28 37 14 19 15 19 10 14 16 14 16 23 28 24 14 23 21 25

1.17 1.35 1.32 1.54 1.62 1.74 1.20 1.58

Regurgitation

1.11 1.46 1.62 1.65 1.07 1.76 1.02 1.13 1.39 1.64 1.60 1.80 1.21 1.83 1.21 1.60 1.39 1.48 1.28 1.67

1+

1+

creased from 81 to 120 beats/min (p < 0.001) and cardiac output increased from 4 ± 1.5 to 6.6 ± 2.2 Llmin (p < 0.001) during exercise. The average transvalvular gradient increased from 8 ± 3 to 12 ± 4 mm Hg (p < 0.001), and the effective orifice area increased from 1.8 ± 0.6 to 2.2 ± 0.6 em- (p < 0.01) (Figs. 3 and 4). The increase in effective orifice area during exercise was negatively correlated with external stent diameter (y = 7.08 - 0.447x; P < 0.01). In patients with an aortic xenograft, the average increase in heart rate response was 86 to 120 beats/min (p < 0.001) and in cardiac output, 4.9 ± 1.2 to 7.8 ± 1.9 Llmin (p < 0.01) during exercise. The average mean transvalvular gradient increased from 21 ± 7 to 27 ± 8 mm Hg (p < 0.001) and the effective orifice area increased from 1.21 ± 0.33 to 1.50 ± 0.36 ern" (p < 0.001) (Fig. 5). A significant correlation between the increase in effective orifice area during exercise and external stent diameter was not noted in patients with an aortic xenograft.

The Journal of

302 Delcan et al.

Thoracic and Cardiovascular Surgery

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Stent Diameter (mm) Fig. 1. The calculated effective mitral orifice area is correlated to the external stent diameter (p = 0.02). The number of patients studied who had a stent size less than 30 mm is small; nevertheless, the data suggest that Angell-Shiley xenografts with a stent diameter less than 30 mm in the mitral position will often be associated with a postoperative calculated effective orifice area less than 1.5 em".

Discussion The postoperative hemodynamic data obtained in this study show the Angell-Shiley xenograft to be moderately obstructive. Among 19 patients who had mitral valve replacement, 10 had a resting gradient greater than 8 mm Hg and seven had an effective orifice area less than 1.5 em"; five patients had an exercise mitral gradient which exceeded 15 mm Hg. Of 29 patients who had aortic valve replacement, 15 had a resting gradient greater than 20 mm Hg and seven had an effective orifice area less than I ern"; 12 patients had an exercise aortic gradient which exceeded 30 mm Hg. The postoperative valve gradients are greater than previously reported for this bioprosthesis. 25 In valve studies with a pulse duplicator, Gabbay and associates" and Wright'" found the Angell-Shiley xenograft to be

Fig. 2. The calculated effective orifice area is correlated to the external stent diameter (p < 0.05). Patients who had a stent size less than 25 mm in the aortic position had a high probability of having a calculated effective orifice area less than 1.0 ern". The scatter within individual stent sizes was less than in the mitral position.

relatively obstructive compared to other bioprostheses of similar stent diameter. The Angell-Shiley xenograft allows a significant increase in effective orifice area at higher flow rates similar to results obtained with other bioprostheses (Fig. 4).15.21. 31 The decrease in tissue inertia at higher cardiac outputs may explain the relative absence of clinical symptoms in the presence of moderate transvalvular gradients. However, the fact that patients were selected for study on the basis of absence of symptoms and that supine leg exercise as performed in this study may not duplicate the usual daily upright exercise that asymptomatic subjects perform may also explain the clinical-hemodynamic discrepancy. The statistical technique of regression analysis may be a useful method to compare the hemodynamic data of different valve series. The technique is relatively independent of the number of valves in individual stent sizes utilized. The different xenografts can be compared by the slope of their regression function and the extrapolated value to the ordinate (predicted effective orifice area). The Gorlin and Gorlin formula may not provide a precise estimate of valve area because the constants

Volume 84

Angell-Shiley xenograft

Number 2

303

August, 1982

I'

_ _7 output-..3.93

grad

c.d

rwa

13 6.2

1.41

1.71

mmHg I/mn

cm2

Fig. 3. Typical hemodynamic results in a patient who had a 30 mm Angell-Shiley xenograft in the mitral position at rest (left) and during moderate supine leg exercise (right) (Patient M-13) .

•

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may vary between prostheses. 30. 31 The hydraulic performance of the xenograft may be influenced by the implant position, which could influence the filling and ejection flow patterns of the left ventricle. Clinical implications. For individual asymptomatic

patients who have an Angell-Shiley mitral xenograft, there is a 95% probability that the postoperative effective orifice area will be greater than 1 ern" if the external stent diameter is 30 mm or more, and there is a 95% probability that the area will be 1.5 em" or more if the

The Journal of

304 Delcan et al.

Thoracic and Cardiovascular Surgery

. 1__-"",,".

mean gracf t _ 3 4

cardiac output I rea

38

mmHg

10.4 I/min 1.51 cm2

4.13

0.69

Fig. 5. The hemodynamic results in a patient who had a 23 mm Angell-Shiley xenograft in the aortic position at rest (left) and during moderate supine leg exercise (right) (Patient A-2).

external stent diameter is 32 mm. If the stent diameter is 30 mm or less, there is a moderate probability that the postoperative effective orifice area will be less than 1.5 ern". For individual asymptomatic patients who have an Angell-Shiley aortic xenograft, there is a 95% probability that the postoperative effective orifice area will be greater than I em" if the external stent diameter is 30 mm or more, and there is a 95% probability that the area will be 0.8 ern" or more if the external stent diameter is 27 mm or more. The likelihood that the postoperative effective orifice area will be less than I em- is high for Angell-Shiley aortic xenografts with a stent diameter of 25 mm or less. The Angell-Shiley xenograft has suboptimal hemodynamic performance characteristics in stent sizes less than 30 mm in the mitral position and less than 25 mm in the aortic position and may provide suboptimal clinical results in adults who have an average body surface area. REFERENCES Carpentier A, Deloche A, Reiland J, Fabiani IN, Forman J, Camilleri JP, Soyer R, Dubost C: Six-year follow-up of glutaraldehyde-preserved heterografts. With particular reference to the treatment of congenital valve malformations. J THORAC CARDIOVASC SURG 68:771-782, 1974 2 Angell WW, Angell JD, Sywak A, Kosek JC: The tissue valve as a superior cardiac valve replacement. Surgery 82:875-887, 1977 3 Oyer PE, Miller DC, Stinson EB, Reitz BA, MorenoCabral RJ, Shumway NE: Clinical durability of the Hancock porcine bioprosthetic valve. J THORAC CARDIOVASC SURG 80:824-833, 1980 4 McIntosh CL, Michaelis LL, Morrow AG, Itscoitz SB,

5

6

7 8

9

10

II

12

13

14

Redwood DR, Epstein SE: Atrioventricular valve replacement with the Hancock porcine xenograft. A five year clinical experience. Surgery 78:768-775, 1975 Zudhi N, Hawley W, Vochl V, Hancock W, Carey J, Greer A: Porcine aortic valves as replacements for human heart valves. Ann Thorac Surg 17:479-491, 1974 Stinson EB, Griepp RB, Shumway NE: Clinical experience with a porcine aortic valve xenograft for mitral valve replacement. Ann Thorac Surg 18:391-401, 1974 Wallace RB: Tissue valves. Am J Cardiol 35:866-871, 1975 Cohn LH, Sanders JH, Collins 11 Jr: Actuarial comparison of Hancock porcine and prosthetic disc valves for isolated mitral valve replacement. Circulation 54:Suppl 3:60-64, 1975 Stinson EB, Griepp RB, Oyer PE, Shumway NE: Longterm experience with porcine aortic valve xenografts. J THORAC CARDIOVASC SURG 73:54-63, 1977 Cevese PG, Gallucci V, Morea M, Dalla Volta S, Fasoli G, Casarotto D: Heart valve replacement with the Hancock bioprosthesis. Analysis of long-term results. Circulation 56:SuppI2:111-116, 1977 Ubago JL, Figueroa A, Colman T, Ochoteco A, Duran CG: Hemodynamic factors that affect calculated orifice areas in the mitral Hancock xenograft valve. Circulation 61:388-394, 1980 Hannah H 1II, Reis RL: Current status of porcine heterograft prostheses. A 5-year appraisal. Circulation 54:Suppl 3:27-31, 1975 Lurie AJ, Miller RR, Maxwell KS, Grehl TM, Vismara LA, Hurley EJ, Mason DT: Hemodynamic assessment of the glutaraldehyde-preserved porcine heterograft in the aortic and mitral positions. Circulation 56:Suppl 2: 104110, 1977 Morris DC, King SB lII, Douglas JS Jr, Wickliffe CW, Jones EL: Hemodynamic results of aortic valvular re-

Volume 84 Number 2

Angell-Shiley xenograft

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\6

17

18

19

20

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23 Lee G, Grehl TM, Joye lA, Kaku RF, Hartec W, DeMaria AN, Mason DT: Hemodynamic assessment of the new aortic Carpentier-Edwards bioprosthesis. Cathet Cardiovasc Diagn 4: 373-381, 1978 24 Rossiter SJ, Miller DC, Stinson EB, Oyer PE, Reitz BA, Moreno-Cabral RJ, Mace JG, Robert EW, Tsagaris TJ, Sutton RB, Alderman EL, Shumway NE: Hemodynamic and clinical comparison of the Hancock modified orifice and standard orifice bioprostheses in the aortic position. J THORAC CARDIOVASC SURG 80:54-60, 1980 25 Angell WW: A nine year experience with the AngellShiley xenograft and a comparative literature review of the porcine bioprosthesis versus the mechanical prosthesis, Bioprosthetic Cardiac Valves, F Sebening, WP Klovelcorn , H Meisner, E Struck, eds., Munich, 1979, Deutsches Herzzentrum, pp 81-106 26 Sandler H, Dodge HT: The use of single plane angiograms for the calculation of left ventricular volumes in man. Am Heart J 75:325-334, 1968 27 Gorlin R, Gorlin SG: Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. I. Am Heart J 41: 1-29, 195\ 28 Sokal RR, Rohlf FJ: Biometria, H Blume, ed., Madrid, 1979, pp 469-509 29 Gabbay S, McQueen DM, Yellin EL, Frater RWM: In vitro hydrodynamic comparison of mitral valve bioprostheses. 1 THORAC CARDIOVASC SURG 76:771-787, 1978 30 Wright JTM: Hydrodynamic evaluation of tissue valves, Tissue Heart Valves, M Ionescu, ed., London, 1979, Butterworths & Co., Ltd., pp 29-88 31 Becker RM, Strom J, Frishman W, Oka Y, Lin YT, Yellin EL, Frater RWM: Hemodynamic performance of the lonescu-Shiley valve prosthesis. J THORAC CARDIOVASC SURG 80:613-620, 1980