The O'Brien-Angell stentless porcine valve: Early results with 150 implants

The O’Brien-Angel1 Stentless Porcine Valve: Early Results With

150 Implants

Ulrik Hvass, MD, Didier Chatel, MD, Patrik Assayag, MD, Mohammad Ouroudji, Yves Pansard, MD, Catherine Lenormand, MD, Thierry Laperche, MD, and Jean-PO1 Depoix, MD Departments

of Cardiac Surgery, Cardiology, and Anesthesiology,

Chirurgie

MD,

Cardio Vasculaire, Hopital Bichat, Paris, France

From August 1991 to June 1994, 150 patients underwent aortic valve replacement with the O’Brien-Angel1 stentless porcine xenograft (Bravo Cardiovascular Model 300, Cryolife, Atlanta, GA). To establish trends we analyzed three consecutive groups of 50 patients. We found significant differences in low postoperative gradients (mean 5 10 mm Hg): 24% in group 1,42% in group 2, and 96% in group 3. Comparing groups 1 and 3, gradients were significantly lower in all valve sizes. The difference is credited to better supraannular positioning of the valve, which is the key to the learning curve. Trivial central

regurgitation was present in the three groups at 6%, 12%, and 0%, respectively. Peripheral regurgitation was trivial in 6%, 8%, and 0%, and mild to moderate in 4%, 2% and 0%, respectively. Seventy-eight of 107 patients with an available follow-up exceeding 1 year had noninvasive controls. Two early cases with moderate perivalvular leaks evolved to moderately severe leaks. Two valves were explanted. The O’Brien-Angel1 stentless valve is easy to handle and correct supraannular positioning provides excellent hemodynamic results.

I

The Patients

nterest in stentless [l-3] porcine valves is increasing. Compared with conventional xenografts, the stentless valves are less cumbersome and should demonstrate improved hemodynamics. They are also expected to offer mechanical features that enhance superior valve longevity 14-71. Despite potential long-term advantages, many questions are still debated. Is the valve suitable for all cases? Is the procedure time-consuming? Is the single running suture technique efficient and safe and what type of suture material should be recommended? Should the valve be placed on the annulus or supraannular? What are the gradients and the incidence of regurgitation? This report on 150 consecutive cases may help formulate some answers. Material

and Methods

The Valve The Bravo Cardiovascular Model 300 Xenograft is a composite design, constructed with noncoronary leaflets obtained from three porcine valves. Leaflets are carefully excised from valves already fixed in glutaraldehyde under very low or near-zero pressure. Individual noncoronary leaflets are matched for size and symmetry to ensure synchronous opening and to promote maximum leaflet coaptation. The matched set of leaflets is sutured together along the free edges of the aortic wall at the leaflet commissures. The base of the valve is finished with a blanket stitch to ensure its integrity. Presented at the VI International Symposium for Cardiac Bioprostheses, Vancouver, BC, Canada, July 29-31, 1994. Address reprint requests to Dr Hvass, Chirurgie Cardio Vasculaire, Hopital Bichat, 46 rue Henri Huchard, Paris 75018,France. 0 1995 by The Society of Thoracic Surgeons

(Ann Thorac Surg 1995;60:5414-7)

DIAGNOSIS GROUPS. Table 1 profiles the diagnosis groups and shows a high proportion of calcified aortic stenosis. AGE GROUPS. The distribution of age groups was as follows: less than 40 years, 15.0%; 40 to 60 years, 16.6%; 60 to 70 years, 24.1%; and older than 70 years, 44.1%. The largest group comprises elderly patients and is correlated with the incidence of calcified aortic valve stenosis. The mean age of patients in the three groups is 54 ? 15, 69.5 2 26 and 78 i- 4.2 years, respectively.

Operative Techniques: Three Groups of Patients In all operations, we placed the patient on normothermic cardiopulmonary bypass maintaining central temperature at 37°C. Myocardial preservation was achieved by antegrade cold blood cardioplegia through the coronary ostia (700 to 1000 mL). Additional 300 mL infusions were repeated every 30 minutes. Pericardial cooling was not used. Before releasing the aortic clamp, warm blood cardioplegia was delivered through the aortic wall at 200 mL per minute for 5 minutes. Spontaneous cardioversion was the rule. The aortic incision was wide and extended to the noncoronary sinus. After excising the valve and decalcifying the annulus, we measured the aortic orifice with a Hegar probe. We rinsed the chosen valve in saline solution like any other bioprosthesis. The valve was then lowered against the aortic annulus and the commissures were positioned. The correspondence between the patient’s annulus and the sewing area of the prosthesis became obvious. Starting with the right coronary sinus, we placed a stitch in the central portion and tied it. This allowed for a moderate traction on the 0003-4975/95/59*50 0003-4975(95)00221-6

Ann Thorac 1995;60:%14-7

CARDIAC

Surg

Diagnosis

N

Calcified aortic stenosis Calcified aortic stenosis with associated lesions Coronary Mitral valve Mitral valve and coronary Subaortic septal obstruction Aortic insufficiency Aortic insufficiency with associated mitral lesions Redo operations Degenerated aortic prosthesis Aortic and mitral prosthesis Aortic and coronary Congenital

71 27 21 3

2 1Y 15 18

stentless valve that facilitated the running suture. We made the same approach with the left, then the noncoronary sinus. Sutures are made with a 4/O or 3/O Prolene (Ethicon, Somerville, NJ) 18 mm half-circle needle. Our implantation technique evolved throughout the experience. The running suture was initially placed on the annulus. Correct supraannular positioning demands that the running suture be placed above and away from the annulus. To analyze the trends produced by the progressive change in technique, we divided the patients into three groups. Group 1 included the first 50 patients and corresponded to a running suture on the annulus. Group 3 included the last 50 patients and corresponded to the correct supraannular positioning. Group 2, comprising patients 51 to 100, represented an intermediate realm and corresponded to the progressive change in technique. Correct supraannular positioning of the xenograft avoided protrusion of any nonvalvular tissue into the outflow tract.

Echocardiography Intraoperative transesophageal echocardiography (TEE) was used only in the first 6 patients. Postoperatively, all patients were evaluated for gradients and regurgitation during the hospital stay or in the first 3 months by echocardiography with Doppler measurements. We recorded the extent of the leak into the left ventricle in parasternal long axis, the width of the leak compared with the diameter of left ventricular outflow tract in M mode color, and flow in the aortic arch and abdominal aorta. The surface of regurgitation was not evaluated in the parasternal short axis. Effective orifice area was measured by the continuity equation.

BIOPROSTHESES STENTLESS

HVASS PORCINE

s415

diameter of the valve was 2 mm smaller than its commercial size. In our series, the valves used were size 21 mm (3.3X;), 23 mm (26.6%), 25 mm (30.0%), 27 mm (23.3”&), and 29 mm (16.6%). Only four valves were 21 mm, corresponding to an annulus of 18 to 19 mm.

Aotiic Cross-clamping Time Figure 1 depicts the aortic cross-clamping time. There is concern that using a stentless porcine valve may prolong aortic cross-clamping time and, consequently, duration of extracorporeal circulation to an extent that may predispose to myocardial damage in multiple cardiac procedures. In cases of isolated aortic calcified valvular stenosis, using the single running suture technique, aortic cross-clamping time ranges from 32 to 70 minutes, with a mean time of 39 minutes. This includes antegrade cardioplegia through the coronary ostia, excising the valve and meticulous decalcification of the patient’s annulus, inserting the prosthesis, closing the aorta, and 5 minutes of warm blood reperfusion before unclamping. Time devoted exclusively to inserting the valve varies from less than 20 up to 30 minutes. Aortic cross-clamping time has therefore always been in what we consider a safe range in our institution.

Operative Mortality No deaths were related to the valve. The 18 perioperative deaths were due to poor preoperative status, such as valvular prosthetic endocarditis (2 cases), emergency operations for critical aortic stenosis (2), and thromboses of a mechanical valve (1). Intercurrent complications in the elderly included respiratory infections (4), renal insufficiency (3), multiorgan failure (3), postoperative cholecystitis (l), and mediastinitis (1 case). Five of 6 patients with active endocarditis (preoperative antibiotics for less than 48 hours, very poor hemodynamic state, urgent operations, positive culture of the valve and surrounding tissues) associated with an aortic annular abscess survived with no recurrence of infection. One patient died at 3 weeks postoperatively of rupture of a splenic aneurysm (mycotic endocarditis).

Early Postoperative Hemodynamics (13 months) Postoperative gradients and regurgitations propriate markers of adequate implantation valves.

Results

Size of Values Used We measured the aortic annulus with a Hegar probe. We then chose a valve 1 to 2 mm larger than the annulus. This did not correspond to oversizing, for the internal

ET AL VALVE

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COMBINED

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are the apof stentless

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Table

CARDIAC BIOPROSTHESES STENTLESS PORCINEVALVE

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Postoperative

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Gradients

Ann Thorac Surg 1995;60:5414-7

ETAL

by Valve

Six

Table

Gradient (mm Hg, mean x SD)

Valve Size

Group 1

(mm)

Group 2

4. Ejkfive

Or$ice

Area

3

Size

Effective Orifice Area (cm’)

Valve Size

Group

by Valve

Group 1

(mm)

Group 3

15 x 7.07

9T1.4

21

1.21

k 0.12

25

79 i 12.72

15 t 9.89

7.5 5 0.7

23

1.15

2 0.07

1.58

2 0.58

27

18 r 12.72

12 5 5.65

8.5 ? 0.7

25

1.12

2 0.25

2.37

t 0.18

29

12 + 7.07

12 i 8.48

27

1.55

2 0.21

2.85

+ 0.87

29

2.05

= 1.2

2.70

t 0.42

23

14.5

5 7.77

7-1.4

” Mean

Postoperative gradients were most often in the low range, 76% being below 15 mm Hg (
+ standard

1.2 i 0

deviation

GRADIENTS.

INCIDENCE OF REGURGITATION. The incidence of regurgitation is summarized in Table 3. Trivial central regurgitation was present in 6% of group 1,12% of group 2, and 0% of group 3 patients. Patch enlargement of the ascending aorta did not have any adverse effects on the occurrence of trivial central leaks (l/32), nor did the presence of a bicuspid valve (l/14). In cases with an annular abscess (all in group 2, accounting for the higher percentage of regurgitations in this group), 4 of 6 had a trivial central leak (and 3 of 6 presented a trivial peripheral leak), revealing the deranged anatomy in such cases and the fragility of the hosts’ tissues. The only patient with a mild to moderate isolated central insufficiency had a 27-mm valve put in a 27-mm annulus, stressing the importance of correctly sizing the prosthesis (group 1). Peripheral regurgitation is trivial in 6X, 8X, and 0% of patients, respectively, and mild to moderate in 4?&, 2’!/,#, and 0%. There have been no cases of significant perivalvular leaks in the last 80 patients, in whom Prolene 410 was replaced by Prolene 310.

Table Group

3. Early

Posfoprrntivp

Type of Regurgitation Trivial central Mild central Trivial peripheral Mild peripheral

Rqyurgitafion

Group 1

by Trcafmcrzt

Croup

2

EFFECTIVE ORIFICE AREA. Table 4 depicts the effective orifice area for groups 1 and 3. Measured by the continuity equation, the effective orifice area is very dependent on precise measures of the subaortic diameter. Large variations in effective orifice area will occur with even small differences in outflow tract estimation. Precise transthoracic measures may be obscured in elderly patients with calcified costosternal cartilages. Transesophageal echocardiography is not always accepted for routine controls. Smaller valve sizes, old age, calcified aortic stenosis, and calcified outflow tracts and mitral valves account for many technical difficulties.

Later Postoperative Hemodynamics (212 months) GRADIENTS. We restudied the records of 76 of 107 patients whose follow-up exceeded 1 year. A greater percentage of patients exhibited a mean transvalvular gradient less than 15 mm Hg (82”/,) when compared with the early postoperative status (68%). ISOLATED CENTRAL REGURGITATION. Echocardiographic studies performed 12 months after patients were discharged from the hospital have shown no difference when compared with early postoperative studies. PERIPHERAL REGURGITATION. The results are unchanged except for patients who initially demonstrated mild to moderate peripheral regurgitation. Two patients have evolved to moderately severe perivalvular regurgitation, accompanied by moderate to moderately severe central regurgitation.

Reoperations Reoperations are summarized in Table 5. Two patients have needed reoperation for peripheral regurgitation at 10 and at 18 months, respectively. One was due to

T&k

Group 3

5. Explanted

Size (mm)

Age (y)

6 ” ,I

72”,N

O”W

29

65

0” 0

2”$,

0” //

27

43

6”,,

8°C)

0 ‘“,I

29

40

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0” 0 41 = aortic

insufficiencv;

Xmografts

Diagnosis AS AI AI

Delay

Cause

10 mo mo 4 mo

Prolene 4/O rupture Slack Prolene 4/O Thrombosis

18

AS = am-tic

stenosis

Ann Thorac Sq

CARDlAC

1995;6O:S414-7

rupture of a 4/O Prolene suture in a patient who initially had a perfect result. The echocardiographic diagnosis in this case had been “massive central regurgitation.” The error is understandable: a peripheral leak on a stented valve would not change the configuration of the leaflets and there would be no central leak, whereas when a stentless valve is not correctly held onto the peripheral annulus, the whole architecture of the valve and the central coaptation is unbalanced. The second reoperation was for a slack 4/O Prolene running suture. The preoperative diagnosis was “peripheral and central regurgitation.” In both cases the leaflets were normal and refixing the valves on the annulus would have been sufficient. Both received mechanical valves.

Comment The majority of patients, and certainly of young patients, in our institution receive mechanical prostheses for aortic or mitral valve replacements. Aortic biological valves are most frequently accepted in patients over 70 years old or in younger patients for whom the referring cardiologist contraindicated anticoagulants. In this present series of cases, young patients needing a bioprosthesis received the porcine stentless valve because homografts were not available. Our present policy is to perform a pulmonary autograft in patients under 45, to use aortic homografts (root replacement technique) in patients between 45 and 65 years old, and to use the porcine stentless valve in patients over 65. In the last 50 cases of porcine stentless valves (patients 100 to 150), 87% were more than 70 years old. The higher-than-normal mortality rate correlates closely with patients’ preoperative status. Elderlv patients in poor general condition that would have been denied operation when we initiated this study have become “an acceptable risk.” Global mortality rates in our institution for valvular operation during the period of the study have been 2.6% in 1991, 3.05% in 1992, and 4.62% in 1993. Correct supraannular positioning of the valve is the key to the learning curve. In the first 50 patients, the valve was placed onto the aortic annulus. Gaining experience, the valve was progressively sewn above the annulus, and then further away from the annulus. The running suture finally held the valve to the aortic wall adjacent to the annulus, rather than to the annulus itself. The consequence is that the small shelf of valvular tissue that previously overlapped the annulus, slightly protruding into the left ventricular outflow tract, was placed into a position leaving the outflow tract free. There has been

BlOPROSTHESES STENTLESS

HVASS ET AL PORCINE VALVE

s417

concern about the aortic wall possibly being a weaker tissue than the annulus itself. Trivial peripheral regurgitation in the three groups is respectively 6%, 8%, and 0%. These results suggest that the aortic wall is sufficiently resistant, even in elderly patients (88% of the patients in group 3 were more than 70 years old). The stress on the suture line is conceivably better absorbed when the valve is seated onto the Valsalva shelf, rather than when undergoing the chiseling effect while hanging onto the annulus. Trivial central regurgitation was noted in 6%, 12%, and 0% of all cases and therefore we conclude it has not been adversely affected by placing the valve slightly away from the annulus. Early gradients are not only related to the valve, but are also influenced by ventricular dynamics, subaortic muscular obstruction in hypertrophied hearts, and by residual postoperative hemodilution and augmented cardiac output. Nevertheless, the results also show a significant difference in the percentage of low mean gradients (less than or equal to 10 mm Hg) in the three groups: 24%, 40%, and 86%, respectively. The higher percentage of low gradients in group 3 is not related to larger valves than in the previous groups. Sizing with the Hegar probe has not been modified throughout the series. Mean postoperative gradients were lower in all valve sizes when comparing groups 1 and 3. The difference came entirely from a better supraannular positioning of the valve. Careful evaluation of the Angell-O’Brien stentless porcine valve will be continued in our institution.

References 1. David TE, Pollick C, Boss J. Aortic valve replacement with stentless porcine aortic bioprosthesis. J Thorac Cardiovasc Surg 1990;99:113-8. 2. O’Brien MF, Clarebrough JK. Heterograft aortic valve transplantation for human valve disease. Med J Aust 1966;2:228-30. 3. Casabona R, De Paulis R, Zattera GF, et al. Stentless porcine and pericardial valves in aortic position. Ann Thorac Surg 1992;54:681-5. 4. Angel1 WW, Oury JH, Lamberti JJ, Koziol J. Durability of the viable aortic allograft. J Thorac Cardiovasc Surg 1989;98: 48-56. 5. Broom ND. Fatigue-induced damage in glutaraldehyde preserved heart valve tissues. J Thorac Cardiovasc Surg 1978;76: 202-l 1. 6 Druxv PJ, Dobrin J, Bodnar E, Black MM. Distribution of flexibility in porcine aortic root and in cardiac frames. In: Bodnar E, Yacoub M, eds. Bioloeical urosthetic valvesproceedings of the Third Interna‘lional’ Symposium. New York: Yorke Medical Books, 1986:580-7. 7 Reis RL, Hancock WD, Yarbrough JW, Glancy DL, Morrow AC. The flexible stent: a new concept in the fabrication of tissue heart valve prostheses. J Thorac Cardiovasc Surg 1971; 62:683-9.