Three-year clinical results with the Monostrut Björk-Shiley prosthesis

J THORAC

CARDIOVASC SURG

1987;94:34-43

Three-year clinical results with the Monostrut Bjork-Shiley prosthesis Between November 1981 and June 1983, 351 patients underwent valve replacement with the Monostrut Bjork-8bi1ey prosthesis. There were 214 aortic valvereplacements, 101 mitral valvereplacements, and 31 double (aortic and mitral) valve replacements. Four patients had valveimplanted in the tricuspid position, and one patient underwent exchange of a valved, extracardiac conduit. Mean age was 61 years (range 2 to 78) and 186 (53%) were male. Concomitant procedures were performed in 52 patients (15%) and 17 (5%) were emergency operations. Early mortality (4.3%) was related to New York Heart Association Functional Class IV, emergency operation, or the presence of a concomitant procedure. FoUow-up was 100% and covered 870 patients-years (mean 2.6 years per operative survivor). Postmortem examination was performed in 38 (79%) of the 48 fatalities. Only one patient suffered a sudden, unexplained death. The 3 year survival rate (early mortality excluded) was 88.6% (aortic valve replacement 89.2%, mitral valve replacement 89.3 %, and double valve replacement 82.5 %). The 3 year freedom from thromboembolism in patients receiving anticoagulants was as foUows: aortic valve replacement 97.5%, mitral valve replacement 92.8 %, and double valvereplacement 100%. There were no instances of valvethrombosis or fatal embolism. In contrast, there were two instances of aortic valvethrombosis among 34 patients having aortic valve replacement without anticoagulation. The 3 year freedom from valve failure (modified Stanford definition) was as foUows: aortic valvereplacement 96.0 %, mitral valvereplacement 93.9 %, and double valve replacement 89.7%. There were no mechanical failures. In conclusion, the Monostrut Bjork-8bi1ey valve showed a low incidence of complications. There were no mechanical failures, no fatal emboli, and, when anticoagulants were administered, no valve thromboses.

Dan Lindblom, M.D., Ulla Lindblom, Axel Henze, M.D., Viking O. Bjork, M.D., and Bjarne K. H. Semb, M.D., Stockholm. Sweden

KarOlinSka Hospital changed to the Monostrut version of the Bjork-Shiley heart valve in November 1981, to eliminate the risk of strut fracture as reported with previous models of this valve.' Even small design changes in a heart valve prosthesis can change its performance characteristics in regard to thrombogenicity,' hemolysis,' perivalvular leakage,' and structural malfunction.' As with any modification, it appeared essential to prospectively define the clinical characteristics, with a presentation of actuarial and linearized rates of complications during the follow-up period. Despite From the Department of Thoracic Surgery, Karolinska Hospital, Stockholm, Sweden. Supported by grants from the Swedish National Association against Heart and Chest Diseases and the Folksam Foundation. Received for publication June 16, 1986. Accepted for publication July 14, 1986. Address for reprints: Dan Lindblom, M.D., Department of Thoracic Surgery, Karolinska Hospital, S-104 01 Stockholm, Sweden.

34

stringent and comprehensive definitions of complications, interobserver variability in applying them will always bias such presentations.' In reporting our experience, we considered it appropriate to include a more detailed description of the complications, to allow individual conclusions as to their clinical significance. The present investigation was undertaken to prospectively collect and analyze information on results after valve replacement with the Monostrut Bjork-Shiley heart valve, and especially to evaluate the incidence and severity of valve-related complications. Hemodynamic and hematologic evaluation of this prosthesis has been done previously':" and was not included in the present study. Material and methods The prosthesis. The Monostrut Bjork-Shiley tilting disc valve consists of a metal cage and pyrolytic carbon disc. The cage is constructed of one solid piece of Stellite by electrochemical and conventional machining tech-

Volume 94 Number 1 July 1987

Monostrut Bjork-Shiley prosthesis

35

Table I. Clinical characteristics of patients receiving Monostrut Bjork-Shiley heart valve prosthesis MVR (n = 10/)

Age (yr)-mean (range) 58 (13-72) 40/60 Male/female (%) 2 Emergency operation (%) NYHA Class (%) 26 34 40 I-II 50 66 III 56 8 IV 10 9 22 5 Previous heart operation 12 (%) 5 Previous valve replacement 4 2 (%) II 65 Atrial fibrillation (%) 30 Heart size (mljm' 595 ± 182 545 ± 161 658 ± 179 BSA)-mean ± SD Valve lesion" (%) 22 Stenosis 51 29 35 Mixed 42 Insufficiency 20 Preoperative history (%) of: 22 42 Congestive heart failure 31 20 Angina pectoris 29 35 9 20 26 Syncope 13 12 Systemicembolism 13 10 Bacterial endocarditis 8 6 Legend: AVR, Aortic valve replacement. MVR, Mitral valve replacement. NYHA, New York Heart Association. BSA, Body surface area. SD, Standard deviation. "Patients with repeat replacement not included (re-AVR = 5, re-MVR = 2).

Diques, It contains no welds. The outflow strut is formed like a single hook with a much broader base than in previous Bjork-Shiley valve models (Fig. 1). According to the manufacturer (Shiley Incorporated, Irvine, Calif.), this prevents strut fracture, even under extreme experimental conditions. The disc is convexo-concave and opens to 70 degrees. This design combined the advantages of the convexo-concave disc-! with anticipated superior durability.' The aortic and mitral prostheses are identical except for the sewing ring, which can be obtained in several configurations, in both Dacron and Teflon material, with or without carbon coating. The device is made in sizes (external diameter) 17 to 33 mm and sizes 29 to 33 mm, differing only in the width of the sewing ring. The distribution of valve sizes used in this series is shown in Fig. 2. The present series also included 49 prototypical Monostrut valves, in which the outflow strut together with a segment of the valve ring was welded into a oorresponding indentation in the valve ring. Apart from themanufacturing process, it was indistinguishable from

Fig. 1. The aortic Monostrut Bjork-Shiley valve prosthesis, viewed from the outflow side. Note integral outflow strut and clearance between disc and ring in the open position. the regular, nonwelded version. Also, we were not able to identify any differences between welded and integrated Monostrut valves in our study. Operative procedure. All operations were performed via a midline sternotomy. Standard cardiopulmonary bypass equipment, moderate (25 to 28 C) general hypothermia, and hypothermic cardioplegic arrest were used. Interrupted 2-0 Ti-Cron sutures, usually without pledgets, were used for the aortic prostheses. The mitral prostheses with a double-flanged sewing ring were anchored with mattress sutures, placed initially in the ventricular flange of the sewing ring and then through the anulus. Pledgets were frequently used in the mitral position. The large opening of the aortic prosthesis was oriented against the convexity of the ascending aorta, whereas it was oriented posteriorly for the mitral prosthesis, if this permitted free movement of the disc. Twelve different surgeons performed the operations. All patients were given prophylactic antibiotic treatment for 3 months, starting the day before the operation. Patients. The series comprised all 351 patients receiving Monostrut Bjork-Shiley valves from November 1981 through June 1983. There were 214 (61%) aortic valve replacements (AVR, of which five were repeat AVR), 101 (29%) mitral valve replacements (MVR, including two repeat MVR), 31 (9%) double (aortic and mitral) valve replacements (DVR), and two tricuspid valve replacements (TVR). One patient had 0

0

36

ThE! Journal of Thoracic and Cardiovascular

lindblom et al.

Surgery

I OF VALVES IMPLANTED

40,----'---'---''---..::.:...----------------,

AlJITIC . VAlVES

c:=:J 30

20

\0

2\

23

25 27 ANNULUS DIAMETER (1iI1I1

29

3\

Fig. 2. Valve size distribution in the series.

Table D. Concomitant procedures in patients receiving Monostrut Bjork-Shiley heart valve prosthesis Concomitant

MVR (n = 101)

procedures (%) Coronary artery bypass grafting Repair/grafting of ascending aortic aneurysm Tricuspid valve anuloplasty Konno aortoventriculoplasty (in children) Others" None

6

3 85

2

0

0 I

4 0

3 83

2 89

Legend: AYR. Aortic valve replacement. MVR, Mitral valve replacement. 'One case each of closure of atrial septal defect, mitral annuloplasty, left ventricular aneurysmectomy, pericardiectomy, closure of aortic periprosthetic leak, repair of Valsalva sinus aneurysm, suture repair of femoral aneurysm, epigastric herniorrhaphy, and carotid endarterectomy.

MVR + TVR and one had replacement of an incompetent systemic atrioventricular valve after a Senning procedure. Finally, one patient underwent exchange of a valved, extracardiac conduit. Six of the 31 patients with DVR received an older version of the Bjork-Shiley valve in the aortic position, making a total of 377 implanted Monostrut valves. Some characteristics of the patient series are presented in Table I, and concomitant surgical procedures are listed in Table II. Anticoagulation protocol. Reheparinization was begun as soon as the chest tubes were removed, usually

on the first postoperative day. At the same time, life-long anticoagulation treatment with dicumarol or warfarin was initiated in all patients receiving a mitral or tricuspid prosthesis and in all but 33 patients undergoing AVR. The efficacy of the anticoagulation treatment was controlled by the Thrombotest method with an aimed therapeutic level of 6% to 12%. The mentioned 33 A VR patients were discharged witt aspirin as the only prophylaxis against thromboembolic complications. Two further patients (one AVR and om DVR) had their warfarin treatment withdrawn postop eratively because of inability to maintain stable Throm botest values. Patient follow-up. All patients referred from the Stockholm area (n = 128) were seen by one of thl authors (D.L.) in the outpatient department at leas once after the operation. These patients, and thos referred from other areas of Sweden or from abroad were contacted every 6 to 12 months by telephone or b: a detailed postal questionnaire. All were primaril: managed at their local hospitals, and those were als contacted for verification and clarification whenever : possible valve-related complication was encountered Hospital records and autopsy reports were scrutinize for valve-related complications. The follow-up ended on Aug. 1, 1985, and was lOOCA complete. A total of 870 patient-years were generated with a mean of 2.6 years per survivor (range 2.2 to 3.~ years). Definitions. Early mortality was defined as dead: within 30 days of operation. Transient ischemic attack denoted any sudden focal

Volume 94 Number 1 July 1987

Monostrut Bjork-Shiley prosthesis

37

Table ffi. Early deaths among 351 patients receiving Monostrut Bjork-Shiley heart valve prosthesis Interval: operationdeath (days)

Autopsy

29

+

2

+

AAA

21

+

AAA

Intraop. II

+

z

3 19

+

Sex, age

Implant site

F, 59

AVR

2

F, 73

AVR

3

M,63

AVR

4 5

F, 66 M,70

AVR AVR

6 7

M,77 M,64

AVR AVR

8

M,68

AVR

CABGx3

4

+

9

M,52

AVR

Hernia repair

8

+

10

M,60

AVR

MVA

24

+

II

M,62 F,67 M,63 F,72 F, 2

MVR MVR DVR DVR Syst AV*

Intraop. 8 19 Intraop. Intraop.

+ + +

Patient No.

12 13 14 15

Emergency operation

Concomitant operation

+

+

+

+

CABG x

+

+

+

Cause of death. comments Valve thrombosis (patient not on anticoagulant) Myocardial infarction (no coronary embolism) Complications after intestinal resection (no mesenteric embolism) Surgical bleeding Myocardial infarction (dissection in left main coronary artery, caused by cardioplegic perfusion cannula) Myocardial failure Intraop. cerebrovascular accident Arrhythmia (sudden death after otherwise normal recovery Myocardial infarction (no coronary embolism) Abdominal complications after bleeding peptic ulcer, emergency gastric resection Acute myocardial failure Myocardial failure Myocardial failure Acute myocardial failure Acute myocardial failure

Legend: AYR.Aorticvalve replacement. MYR, Mitralvalve replacement. DYR,double (aorticand mitral)valve replacement. AAA, Repair/graftingof ascending aortic aneurysm. CABG,Coronaryartery bypass grafting. MYA, Mitral valve annuloplasty. ·Replacement of incompetent systemic atrioventricular valve after Senning repair of transposition of the great arteries.

neurologic deficit lasting less than 24 hours. Embolism was defined as any sudden focal neurologic deficit persisting more than 24 hours or any sudden symptom related to obstruction of a systemic artery. Cerebrovascular accidents occurring intraoperatively were not considered to be valve-related embolism. Valve thrombosis was defined as any thrombotic material impeding free movement of the disc. Anticoagulant-related hemorrhage included any nontraumatic bleeding necessitating hospital admission or blood transfusion or causing the patient's death. Prosthetic valve endocarditis was defined as any infection of the prosthesis or periprosthetic area documented at rooperation or autopsy, regardless of the results of blood cultures. Our definition of valve failure is a modification of that used by the Stanford group." We thus classified as valve failure any valve-related complication (including

anticoagulant-related hemorrhage) leading to rooperation (not only rereplacement) or to the patient's death. Statistical methods. Risk factors for early mortality were analyzed in a univariate fashion by means of contingency tables and chi square or Fisher's exact method. Factors considered were age «70 versus 2: 70 years), sex, implant location (AVR versus MVR versus DVR), New York Heart Association (NYHA) classification (Class I-II versus III versus IV), status of operation (elective versus emergency), concomitant procedures, cross-clamptime (::5120versus> 120 minutes), previous heart operation, history of congestive heart failure, angina pectoris, syncope, or embolism, left ventricular end-diastolic pressure (::525 versus >25 mrn Hg), radiologic heart size,and cardiac rhythm. The null hypothesis was rejected if p < 0.05. Survival (early mortality excluded)and freedom from complications were determined according to standard

38

The Journal of Thoracic and Cardiovascular Surgery

lindblom et al.

Table IV. Late deaths, without autopsy, after implantation of Monostrut Bjork-Shiley heart valve prosthesis Interval: operation -death (mo)

Patient No.

Assumed cause of death

IS

Cancer

2

F,68

AVR

31

Cancer

3

M,60

AVR

31

Cancer

4

M,62

MVR

29

5

M,42

DVR

14

Nontraumatic cerebral bleeding ? (sudden, unexplained)

6

M,65

DVR

8

Congestive heart failure

7

M,71

DVR

6

Myocardial infarction

8

F, 60

TVR

2

Congestive heart failure

Comments Disseminated, biopsy-proved prostatic carcinoma Recurrence of previously resected intestinal carcinoma Exploratory thoracotomy disclosed nonresectable lung cancer Died after craniotomy: Thrombotest <5% Found dead in bed at home: Congestive heart failure throughout postop. period Intraoperative entrapment of mitral disc by long chorda tendinea: Persistent, severe congestive heart failure throughout postop. period Died 9 days after acute myocardial infarction, diagnosed from ECG and enzyme release. Previously A VR + MVR + tricuspid annuloplasty; present procedure = TVR + repair of aortic periprosthetic leak; severe congestive heart failure in the postop. period; died at home

Legend:AYR. Aorticvalve replacement. MYR, Mitralvalve replacement. DYR,Double (aorticplusmitral)valve replacement. TYR,Tricuspid valve replacement. ECG, Electrocardiogram.

actuarial formulas.'? II Differences between actuarial curves were studied with the Mantel-Haenszel procedure." Actuarial point estimates and binomial proportions are given as percentages, with 95% confidence limits (CL). Linearized complication rates are presented as events/loo patient-years ± standard error. Results Early mortality. There were 15 deaths within 30 days of operation (4.3%, 95% CL 2.0%-6.5%), including four intraoperative deaths (1.1%, 95% CL 0.30/0-3.0%). Autopsy was performed in 13 (87%) of these 15 patients. The causes of early death and some clinical information are presented in Table III. One fatal valve thrombosis occurring 29 days postoperatively and one death from a bleeding peptic ulcer (Patients I and 10, Table III) were, by definition, considered valve-related deaths. The early mortality rates for different implant locations were as follows: AVR 10/214, 4.7% (95% CL 2.30/0-8.5%); MVR 2/101,2.0% (95% CL 0.2%-7.0%); and DVR 2/31, 6.5% (95% CL 0.80/0-21.4%). This variation in mortality did not reach statistical signifi-

cance. The following factors were associated with increased early mortality: emergency operation (p < 0.01), NYHA Class IV (p < 0.05), and concomitant surgical procedures (p < 0.05); all represented more advanced disease. The early mortality rate in patients undergoing isolated, elective AVR was 1.2% (2/162, 95% CL 0.20/0-4.4%), whereas it was 2.3% (2/88, 95% CL 0.3%-8.0%) after isolated, elective MVR. Late mortality. Thirty-three patients died late. Postmortem examinations were performed in 25 of these patients (76%). The remaining eight patients are described in Table IV. Seventeen patients died of myocardial failure, which in eight cases was due to myocardial infarction. In none of these could a coronary embolus be identified, but advanced coronary arteriosclerotic disease was found in all. One late death from myocardial failure probably was related to a prolonged operation, caused by entrapment of the mitral disc by a too long chorda tendinea (Patient 6, Table IV). Two patients died of rupture of ascending aortic aneurysms. Two patients died in connection with valve rereplacement because of prosthetic

Volume 94 Number 1

Monostrut Bjork-Shiley prosthesis

July 1987

39

I stJIYIVAI.

Table V. Linearized rates (eventsjlOO patient-years ± standard error) of complications among 316 patients receiving anticoagulant treatment after implantation of Monostrut Bjork-Shiley heart valve prosthesis

lror~

:~

~

80

MVR

116

113

112

Complications

(n = 10/)

219

207

201

Transient ischemic attack Embolism Fatal embolism Valve thrombosis All thromboembolic complications

1.9 ± 0.8 1.7 ± 0.5 0 0 3.6 ± 0.7

1.2 ± 0.5 0 0 3.5 ± 0.9

3.1 ± l.l 0 0 5.0 ± 1.4

Bleeding* Fatal bleeding*

2.2 ± 0.5 0.5 ± 0.3

3.0 ± 0.8 0.7 ± 0.4

1.5 ± 0.8 0.4 ± 0.4

Prosthetic valve endocarditis Valve failuret Reoperation Mechanical failure Sudden unexplained death

0.4 ± 0.2

0.5 ± 0.3

0.4 ± 0.4

1.9 ± 0.5 1.4 ± 0.4 0 0.1 ± 0.1

1.4 ± 0.6 0.7 ± 0.4 0 0

2.3 ± 0.9 1.9 ± 0.9 0 0

'Includes a caseof fatal bleeding in the early postoperative period. tModified Stanford definition.

valve endocarditis, and two died of noninfectious valve dehiscence. Three patients receiving warfarin died of cerebral bleeding; one of them of a ruptured intracerebral aneurysm, one after operation for intracerebral bleeding, and one of bleeding in an intracranial tumor. This last patient did not receive anticoagulant treatment during the first postoperative month after A VR, but was later incorporated in the anticoagulation program. At autopsy, thrombotic material was found on the sewing ring of the prosthesis, but this had not interfered with disc movements. Intracerebrally, there was a large bleeding site, and at histologic examination a papilloma in the choroid plexus was documented, in which the bleeding probably had started. One patient died after massive subcutaneous bleeding, thought to represent aeptic complications, but all blood cultures were negative and therewas no sign of prosthetic valve endocarditis at .the postmortem examination. The patient was classified as having died of anticoagulant-related hemorrhage. Malignant disease caused death in four patients and there was one sudden, unexplained death. Finally, one ptient died of aortic valve thrombosis, which was Qlused by omission of her anticoagulant treatment. Altogether, nine of the 33 late deaths (27%, 95% CL 13%-46%) were considered the result of valve-related oompli.cations, including valve thrombosis (n = 1),

o =NYIIA I-II 1!i.611 I

=NYIIA III-IV (84.11ll

: } PATIENTS AT RISK

o = NVR 189.311 = AVA 189.211 +=DVA 182.511

I

80

60

1=95

40 20 0

0

99

!l6

95

204

195

191

29

27

25

12

24

a.

: } PATIENTS AT RISK

:Ii

IOOHS Pl!iT-(JI

Fig. 3. Actuarial survival after replacement with the Monostrut Bjork-Shiley valve. Patients are stratified according to implant location (lower panel, A) and preoperative NYHA classification (upper panel, B). AVR. Aortic valve replacement. MVR. Mitral valve replacement. DVR. Double (aortic and mitral) valve replacement. NYHA. New York Heart Association. 95CL, 95% confidence limits. NS. Not significant.

bleeding (n = 4), prosthetic valve endocarditis (n = 2), and noninfectious periprosthetic leakage (n = 2). The overall 3 year actuarial survival rate was 88.6% (95% CL 84.7%-92.5%). Actuarial presentation of late mortality with patients stratified according to implant location and preoperative NYHA class is given in Fig. 3. No significant differences were noted between different valve locations, but NYHA Classes III and IV were associated with increased late mortality (p < 0.05). Thromboembolism. Embolism occurred 16 times in 13 patients, five of whom were asymptomatic at the time of most recent follow-up. Three patients had minor symptoms, not interfering with their daily activities. Two patients had permanent visual field defects, and three were incapacitated by hemiparesis. No embolic complication was fatal. In addition, 19 patients had a transient ischemic attack, with complete recovery within 24 hours (in 17 patients within 20 minutes). Atrial fibrillation was not identified as a risk factor for thromboembolism.

The journal 01 Thoracic and Cardiovascular Surgery

40 lindb/om et a/.

~

FREEDOM FROM THROMBOEMBOLISM

1OOl=4

=

~

: : tIl

+ .. OVR (100X) If .. AVR (97.5X) o .. MVR (92.8X)

BO

40

20

0

1-

B

60

0

30

28

24

180

163

158

101

94

88

12

24

:Jl

95

CL

+

36

PATIENTS AT RISK

MONTHS POST-OP

Fig. 4. Actuarial freedom from thromboembolism (embolism or valve thrombosis). Only patients receiving anticoagulant treatment are considered. For abbreviations see Fig. 3.

Actuarial estimates of freedom from thromboembolism are given in Fig. 4, and linearized rates of the various complications, including thromboembolism, in Table V. This table includes only patients receiving long-term anticoagulation treatment. None of them had valve thrombosis. There were three episodes of embolism (not causing permanent deficits) and two fatal instances of aortic valve thrombosis (one within 30 days of operation, Patient 1, Table III) among the 35 patients without anticoagulation treatment. The time during which these patients were without warfarin ranged from 29 days to 13 months, accumulating to less than 15 patient-years. Anticoagulant-related hemorrhage. Nineteen patients had a total of 20 episodes of anticoagulant-related hemorrhage, of which four (20%, 95% CL 90/0-47%) were fatal. Three episodes of bleeding necessitated operative intervention (one fatality) and nine necessitated blood transfusions. In three of the patients with a fatal anticoagulant-related hemorrhage, the Thrombotest value was below 5% at the time of bleeding, and in the fourth patient the value was not known. Prosthetic valve endocarditis. Prosthetic valve endocarditis occurred in three patients, all of whom underwent reoperation, with two early deaths and one longterm survival. Positive cultures were not found in any patient, but the surgical findings were typical for prosthetic valve endocarditis. Periprosthetic leakage. Periprosthetic leakage not

caused by infection necessitated reoperation (with suture repair) in eight patients and was fatal in two, one with and one without reoperation. Valve failure. According to our defined criteria, there were eleven fatal valve-related complications (two early and nine late) and eight nonfatal reoperations. There were no mechanical failures. Actuarial freedom from valve failure is summarized in Fig. 5. Discussion Valve replacement is well established as the treatment of choice for most significant valve lesions. Current mechanical valves and bioprostheses serve as acceptable substitutes from a hemodynamic point of view, at least in the medium and large sizes. Mechanical valves are usually preferred in Sweden, mainly because of superior durability but also because of an efficient surveillance system, allowing optimal anticoagulation treatment. However, disruption of mechanical heart valves, thromboembolism, and anticoagulant-related hemorrhage have occurred. The search for more durable and less thrombogenic devices is an ongoing, probably neverending process. This study dealt with incidence and severity of valve-related complications after implantation of a recently introduced modification of the Bjork-Shiley tilting disc valve. Survival is only partly related to valve design, and some patient-related factors are stronger determinants

Volume 94 Number 1

Monostrut Bjork-Shiley prosthesis 41

July 1987

FREEDOM FROM VALVE FAILURE

~

100

TT

~

*-

AVR

a - MVR

(96.0~)

(93.9~)

+ - DVR

(89.

7~)

80

60

1-

~

95

CL

40

20

0

214

194

191

101

93

92

31

26

22

0

12

24

:1 """"" "

RISK

36

MONTHS POST-OP

Fig..5. Actuarial freedom from valve failure (modified Stanford criteria). For abbreviations see Fig. 3.

Table VI. Summary of results obtained with currently used mechanical heart valve prostheses

J

Ref No.

Authors

Prostheses

14 15 16

Semb et al. Baudet et al. DeWall et al. Present series

Medtronic Hall St. Jude Medical Omniscience Monostrut Bjork-Shiley

14 IS

16

14 IS

16

Semb et al. Baudet et al. DeWall et al. Present series

Medtronic Hall St. Jude Medical Omniscience Monostrut Bjork-Shiley

Semb et al. Baudet et al. DeWail et al. Present series

Medtronic Hall 51. Jude Medical Omniscience Monostrut Bjork-Shiley

AVR

MVR

DVR

Three-year survival (%)

87 95 85 89

83 90 86 89

91 95 83

Three-year freedom from embolism (%)* 97 92 Not stated in actuarial terms

96 98

95 93

100

Three-year freedom from valve thrombosis (%)* Not stated in actuarial terms

100 96 100

100 95 100

100 100

"Only patients receiving maintenance anticoagulation therapy.

of short-term and long-term survival." In the present series, NYHA Classes III and IV represented an important risk factor in total mortality, whereas only NYHA Class IV was associated with increased early mortality. A compilation of results reported for a number of other valves is presented in Table VI. The references wereselected from clinics with long experience with the respective devices.P'" The differences noted regarding survival and thromboembolism in Table VI are small. Theonly notable difference is the high incidence of valve thrombosis in one of the series," in which valve throm-

bosis also represented 91% of all significant thromboembolism. Some of these patients had temporary changes in their anticoagulation treatment shortly before the occurrence of thromboembolism, an experience corroborated in the present study. Our finding of two instances of valve thrombosis among the AVR patients not receiving warfarin was similar to experience with the bileaflet St. Jude Medical aortic prosthesis, with five cases of valve thrombosis among 67 patients treated with aspirin and dipyridamole" and four cases among 65 not receiving anticoagulants." Because of this clinical experience, we do not consider aspirin effective in

4 2 Lindblom et al.

preventing clotting of the prosthesis, and we believe it probably also provides a suboptimal protection against embolism. Bleeding complications are related to the quality of the anticoagulation program and not to the design of the prosthesis as such. Valve failure, as defined by the Stanford group" and as used with modification in this presentation, will be influenced by the efficacy of the anticoagulation treatment. Prosthetic valve endocarditis, a complication more associated with patient-related factors than valve design," will in tum influence the rate of valve failure. Likewise, periprosthetic leakage is more associated with surgical technique" and experience than with the choice of valve substitute. In their definition of valve failure, Miller and assoelates" included all valve-related complications (also anticoagulant-related hemorrhage) causing either the patient's death or rereplacement of the valve. Their definition did not include reoperations without rereplacement, so that patients undergoing thrombectomy for valve thrombosis or suture repair of periprosthetic leakage were excluded. Because these complications must be regarded as treatment failures, at least from the patient's point of view, we included them in our definition of valve failure. This modification of the "Stanford definition" in fact increased our actuarial incidence of valve failure by 61 %, by including seven nonfatal repairs for periprosthetic leakage. Despite these shortcomings, our concept of valve failure may serve as a useful parameter in evaluating results after valve replacement operations. When comparing results from various centers, one must be aware that the rate of the different complications is not constant, giving preference to actuarial methods over comparisons between linearized rates. Thromboembolism,"!' prosthetic valve endocarditis, I 8 and valve failure" are examples of complications with peak incidence during the first postoperative year(s), whereas bioprosthetic degeneration is more common later on." When linearized rates are being reported in short-term studies, this will skew the results and imply a higher incidence for complications occurring early. Just by increasing the length of follow-up, these early complications will be diluted in a larger pool of years, which lowers the linearized rates. The present investigation demonstrates an incidence of valve-related complications comparable with other current prostheses.":" Previous studies of the Monostrut Bjork-Shiley valve-" demonstrated excellent hemodynamic characteristics and insignificant hemolysis. With a prospective, 100% complete follow-up, including an autopsy rate of 79% among all fatalities, and with only

The Journal of Thoracic and Cardiovascular Surgery

one instance of sudden unexplained death during a follow-up period covering 870 patient-years, the risk of any serious undetected valve-related complication should be very low. In conclusion, we find the Monostrut Bjork-Shiley valve prosthesis to be a reliable valve substitute with an acceptable incidence of complications. The present 3 year results, with no mechanical failure, no fatal embolism, and no valve thrombosis in patients receiving anticoagulants, encourage its further use. REFERENCES I. Bjork YO. Metallurgic and design development in response to mechanical dysfunction of Bjork-Shiley heart valves. Scand J Thorac Cardiovasc Surg 1985;19:1-12. 2. Marshall WG Jr, Kouchoukos NT, Pollock SB, Bradley EL. Early results of valve replacement with the BjorkShiley convexoconcave prosthesis. Ann Thorac Surg 1984;37:398-403. 3. Bonchek LI, Starr A. Ball valve prostheses: current appraisal of late results. Am J Cardiol 1975;35:843-54. 4. A1strup P, Rygg IH. Experience with Omniscience and Lillehei-Kaster valves [Letter]. J THORAC CARDIOVASC SURG 1984;87:940. 5. McGoon DC. The risk of thromboembolism following valvular operations. How does one know? J THORAC CARDIOVASC SURG 1984;88:782-6. 6. Aris A, Crexells C, Auge JM, Oriol A, Caralps JM. Hemodynamic evaluation of the integral Monostrut Bjork-Shiley prosthesis in the aortic position. Ann Thorac Surg 1985;40:234-40. . 7. Bjork YO, Lindblom D. The Monostrut Bjork-Shiley heart valve. J Am Coli Cardiol 1985;6:1142-8. 8. Aberg B, Holmgren A. Haemodynamic evaluation of the convexo-concave Bjork-Shiley prosthesis in patients with narrow aortic annulus. Scand J Thorac Cardiovasc Surg 1981;15:111-6. 9. Miller DC, Oyer PE, Stinson EB, et al. ten to fifteen year reassessment of the performance characteristics of the Starr-Edwards Model 6120 mitral valve prosthesis. J THORAC CARDIOVASC SURG 1983;85:1-20. 10. Cutler SJ, Ederer F. Maximum utilization of the life table method in analyzing survival. J Chron Dis 1958;8:699712. II. Grunkemeier GL, Lambert LE, Bonchek LI, Starr A. An improved statistical method for assessing the results of operation. Ann Thorac Surg 1975;20:289-98. 12. Mantel N. Evaluation of survival data and two new rank order statistics arising in its consideration. Cancer Chemother Rep 1966;50:163-70. 13. Blackstone EH, Kirklin JW. Death and other time-related events after valve replacement. Circulation 1985;72:75367. 14. Semb BKH, Hall KY, Nitter-Hauge S, Abdelnoor M. A 5 year follow-up of the Medtronic-Hall valve: survival and

Volume 94 Number 1 July 1987

thromboembolism. Thorac Cardiovasc Surg 1983;31:61-

5. IS. Baudet EM, Oca CC, Roques XF, et al. A 5V2 year experience with the St. Jude Medical cardiac valve prosthesis. J THORAC CARDIOVASC SURG 1985;90:13744. 16. DeWall R, Pelletier LC, Panebianco A, et al. Five-year clinical experience with the Omniscience cardiac valve. Ann Thorac Surg 1984;38:275-80. 17. Ribeiro PA, Al Zaibag M, Idris M, et al. Antiplatelet drugs and the incidence of thromboembolic complications of the St. Jude Medical aortic prosthesis in patients with rheumatic heart disease. J THORAC CARDIOVASC SURG 1986;91 :92-8.

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18. Ivert TsA, Dismukes WE, Cobbs CG, Blackstone EH, Kirklin JW, Bergdahl LAL. Prosthetic valve endocarditis. Circulation 1984;69:223-32. 19. Dhasmana JP, Blackstone EH, Kirklin JW, Kouchoukos NT. Factors associated with periprosthetic leakage following primary mitral valve replacement: with special consideration of the suture technique. Ann Thorac Surg 1983;35:170-8. 20. Gallucci V, Bortolotti U, Milano A, Valfre C, Mazzucco A, Thiene G. Isolated mitral valve replacement with the Hancock bioprosthesis: a 13-year appraisal. Ann Thorac Surg 1984;38:571-8.