Five-year clinical experience with the Omniscience cardiac valve

Results of valve replacement with Omniscience mechanical prostheses

BACKGROUND

The Omniscience mechanical valve has been the subject of multiple clinical investigations with variable results, including reports of high complication and reoperation rates.

METHODS

Records of all patients who received Omniscience valves were reviewed, and follow-up interviews were conducted to determine the incidence of valve-related morbidity, mortality, and functional results. Incidence of complications was expressed as events per 100 patient-years follow-up. Survival and freedom from valve-related complications and mortality were calculated using a product limit method.

RESULTS

Between 1984 and 1988, 192 patients received 213 Omniscience valves [93 mitral (M), 79 aortic (A), and 20 multiple (D) valve replacements]. Perioperative mortality was 9%. The incidence of major valve-related morbidity was as follows: thrombosis, 1.30 M, 0.17 A, 0.72 D; endocarditis, 0.48 M, 0.18 A, 0 D; hemorrhagic, 4.67 M, 2.84 A, 5.00 D; embolic, 2.90 M, 2.27 A, 1.57 D; nonstructural dysfunction, 1.66 M, 1.08 A, 2.27 D; reoperation, 4.02 M, 1.99 A, 6.48 D. All explanted valves (n = 43) were examined, and 40% (n = 17) were found to have limited disc excursion in the absence of thrombus. Freedom from valve-related morbidity, mortality, or reoperation at 10 years was 22% for mitral, 39% for aortic, and 17% for multivalve replacements. At follow-up, only 73% of patients were New York Heart Association class I or II. Five- and 10-year estimated survivals were 72% and 55% for M, 80% and 51% for A, and 65% and 50% for D replacements.

CONCLUSIONS

Use of the Omniscience valve provided poor functional improvement and a significant incidence of valve-related complications, including the need for reoperation.

Aortic valve replacement with omniscience and omnicarbon valves

Clinical results achieved in 100 cases of aortic valve replacement with the Omniscience (O-S) valve during the period from 1980 to 1985 as well as 100 cases of aortic valve replacement with the Omnicarbon (O-C) valve during the period from 1985 to 1989 were studied. Concomitant surgical procedures including mitral valve replacement were performed in 63 patients in the O-S group and 67 patients in the O-C group. Cumulative follow-up in the two groups was carried out for a total of 559 and 273 patient-years, respectively. The overall 4-year actuarial survival rate was 82% +/- 3.8% in the O-S group and 89.5% +/- 3.2% in the O-C group, the corresponding rates for patients undergoing isolated aortic valve replacement being 82.9% +/- 4.2% in the O-S group and 91.9% +/- 3.5% in the O-C group. The overall 4-year actuarial event-free rate with respect to thromboembolic complications was 88.8% +/- 3.3% in the O-S group and 94.4% +/- 2.8% in the O-C group, as compared with the corresponding rates of 89.2% +/- 3.6% in the O-S group and 95.9% +/- 2.8% in the O-C group for patients undergoing isolated aortic valve replacement. The overall rate of valve-related complications, including thromboembolism, anticoagulant-related hemorrhage, perivalvular leak, infection, and structural failure, was 78.8% +/- 4.2% in the O-S group and 89.3% +/- 3.5% in the O-C group (p less than 0.05), and for isolated aortic valve replacement, 79.7% +/- 4.5% in the O-S group and 89.6% +/- 4.1% in the O-C group.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical cardiac valvular prostheses

Mechanical cardiac valvular prostheses currently enjoy a 60% to 40% market-share advantage over tissue prostheses in the United States and worldwide. Only the Starr-Edwards caged Silastic (Dow Corning) ball, Medtronic-Hall, St. Jude Medical, and Omniscience valves remain available in the United States. Although each valve has certain advantages and disadvantages, no design has achieved functional mechanical perfection. Late follow-up of valve-related complications from the literature favors the St. Jude Medical and Medtronic-Hall valves.

Thrombotic and bleeding complications of prosthetic heart valves

A review of articles published since 1979 indicates that thrombotic and bleeding complications account for about 50% of valve-related complications in patients with bioprosthetic aortic and mitral valves and for approximately 75% of the complications in patients with mechanical valves. Although compromised by lack of standard definitions and by variability in reporting and follow-up, the data suggest that the linearized rate of both thrombotic and bleeding complications in patients with aortic bioprostheses is approximately half that for aortic mechanical prostheses (2% versus 4%), but is approximately equal for both bioprostheses and mechanical valves in the mitral position (approximately 4%), and for mechanical and bioprosthetic aortic and mitral valves in combination. However, linearized rates for fatal thrombotic and bleeding events are two to four times higher in patients with mechanical prostheses. The adequacy of warfarin anticoagulation is the most important factor affecting thrombotic and bleeding complications in patients with mechanical valves and over shadows the dubious importance of other phenomena such as atrial fibrillation and left atrial thrombus. Short-term warfarin anticoagulation or the use of long-term platelet inhibitors, or both, do not appear to reduce the incidence of thrombotic complications in patients with aortic bioprostheses but increase bleeding. For mitral bioprostheses, the postoperative use of warfarin for three months or aspirin indefinitely is as effective in preventing thromboembolism as long-term warfarin. Acute prosthetic valve endocarditis is associated with a 13 to 40% incidence of thrombotic complications. Likewise, the recurrence rate of cerebral emboli is high (20-30%) in patients with prosthetic valves who are not anticoagulated. Bioprostheses are strongly preferred for women who wish to bear children; fetal wastage occurs in 25 to 30% of pregnant women with mechanical heart valves who receive either warfarin or heparin, or a combination of the two. Heparin, however, greatly increases the risk of maternal bleeding. In children, the efficacy of platelet inhibitors without warfarin anticoagulation is unproven; nearly all serious strokes occur when warfarin is omitted; and permanent disability from warfarin-related bleeding is rare. All prosthetic cardiac valves initiate coagulation and affect the dynamic equilibrium between activated procoagulants and endogenous anticoagulants. Warfarin is the only available oral exogenous anticoagulant.(ABSTRACT TRUNCATED AT 400 WORDS)

Intermittently stuck occluder: case report of an unusual complication with the use of an aortic Omniscience prosthesis

An occluder which intermittently became stuck in the open position with concomitant aortic regurgitation was encountered in a patient subjected to an aortic valve replacement with a 23 Omniscience prosthetic valve. The patient was intermittently aware of the complete momentary disappearances of the valve sounds, the etiology of which could not be discerned. During fluoroscopic examination, the occluder became stuck for a few cardiac cycles in what appeared to be the fully open position before finally moving. Prosthetic valve malfunction was thus diagnosed. The emergency operation was successful. Operative findings revealed that a thin thrombus had developed in a curtain-like fashion on the left ventricular face of the prosthesis with mild tissue overgrowth along the perimeter of the valve. The Omniscience prosthesis was replaced with a 19-mm St. Jude Medical prosthesis, and the patient's postoperative course has been uneventful.

A six-year study of the Omniscience valve in four Canadian centers

Stimulated by the recent controversy over the Omniscience valve, we conducted a follow-up study on 413 hospital survivors in whom this prosthesis was implanted at four Canadian centers from 1979 to 1985. One hundred forty-seven underwent aortic valve replacement (AVR), 203 had mitral valve replacement (MVR), 10 had tricuspid valve replacement (TVR) and 53 underwent multiple valve replacement (45 AVR + MVR, 5 MVR + TVR, and 3 AVR + MVR + TVR). The mean age was 50.8 +/- 13 years (range, 2 months to 75 years). Follow-up of 96% was achieved for a mean of 2.6 years and a maximum of 6 years with a total of 1,076 patient-years. Complications were defined and graded according to severity. Analyses were performed to yield linearized and actuarial rates for complications. There were 30 late deaths (2.8% per patient-year). At 5 years, the actuarial survival was 89 +/- 3% (AVR, 89 +/- 3% and MVR, 91 +/- 3%). Percentages for freedom from each complication are as follows: endocarditis, 96 +/- 1% (AVR, 96 +/- 2% and MVR, 98 +/- 1%); periprosthetic leak, 99 +/- 0.6% (AVR, 98 +/- 1% and MVR, 99 +/- 0.6%); thrombotic complications, 87 +/- 3% (AVR, 84 +/- 6% and MVR, 90 +/- 3%); valve thrombosis 99.4% (AVR and MVR, 100%); anti-coagulant-related hemorrhage, 94 +/- 2% (AVR, 97 +/- 2% and MVR, 94 +/- 2%); and all valve-related complications, 77 +/- 3% (AVR, 77 +/- 6% and MVR, 79 +/- 4%). Reoperation was required at the rate of 1.2% per patient-year.(ABSTRACT TRUNCATED AT 250 WORDS)

The determinants of mortality and morbidity after multiple-valve operations

The factors predictive of hospital mortality and morbidity after contemporary multiple-valve surgical procedures were identified to develop strategies to improve the results of such procedures. Preoperative, intraoperative, and postoperative information was collected prospectively on 90 consecutive patients undergoing surgical procedures between 1982 and 1984. The operative mortality was 5.6%, and the incidence of postoperative low-output syndrome was 16.7%. Multivariate logistic regression analysis identified tricuspid regurgitation (p less than .03, improvement-of-fit chi square) and the aortic valve lesion (p less than .03) as the independent predictors of postoperative complications (mortality or low-output syndrome). Patients with tricuspid regurgitation and right ventricular decompensation and those with aortic stenosis and left ventricular hypertrophy had limited ventricular functional reserve and faced an increased risk. Improved methods of myocardial protection may reduce the risk in these patients.

Reoperations for left-sided low-profile mechanical prosthetic obstructions

A series of 2,474 hospital survivors of primary mitral, aortic, and double mitral-aortic valve replacement were observed for a cumulative period of 11.945 years (mean, 4.2 years; range, 0.6-14 years). The linearized incidences of reoperations for thrombotic obstructions were 0.33 +/- 0.08% for mitral valve replacement, 0.36 +/- 0.1% for aortic valve replacement, and 0.42 +/- 0.1% for double valve replacement (p = not significant). Forty-one patients (16 mitral, 12 aortic, and 13 double valve replacements) underwent a total of 44 reoperations with a mean interval of 36 +/- 29 months (range, 0.25-85 months) between operations. Diagnosis was established invasively only in 13 patients (30%). Hospital mortality at reoperation was 18% (8 patients); 28 patients (63%) required emergency surgery. The choice surgical procedures were thrombectomy for clotted aortic prostheses (18 of 24) and valve replacement for obstructed mitral valves (22 of 25; p less than .001). Rethrombosis occurred in 3 patients (1 aortic and 2 double valve replacements). At hospital admission 17 patients (38%) had prothrombin times outside therapeutic ranges (between 20 to 30% of the normal value). The incidence of reoperations for thrombosis in low-profile mechanical prostheses was unaffected by valvar position and number of prostheses implanted. Rethrombosis occurred only in previously cleaned valves, although its occurrence was not significant. The present results indicate that, as experience is gained in the diagnosis and surgical management of this complication, hospital mortality can be reduced significantly (from 37% to 4%).

Clinical evaluation of the Omniscience aortic disc valve prosthesis

The clinical results and hemodynamics were evaluated in 100 cases of aortic valve replacement, using the Omniscience valve, in the period December 1980 through 1984. Late survival rate, clinical improvement and cardiac and prosthetic valve performance were acceptably satisfactory. The overall incidence of thromboembolism was 4.7%/patient year. The opening angle of the disc was less than 60 degrees in 18% of the studied cases. Further investigations are required to determine if such results were related to the valve structure or to some cause in the recipient. Assessment of the durability of the Ominiscience cardiac valve prosthesis must await the results of long-term observation.

Six year clinical study of use of the Omniscience valve prosthesis in 219 patients

A 6 year experience of cardiac valve replacement with the Omniscience prosthesis is described. A total of 253 valves were inserted in 219 patients. The survivors were followed up for a total of 536 patient-years and for a mean of 2.8 years. The follow-up was 97.6% complete. Analyses were performed in accordance with recommended criteria regarding definitions of complications and grading thromboembolic events for severity and analysis of anticoagulant status. Results are described both in terms of actuarial and linearized rates. For the patients at risk, actuarial survival at the end of 5 years was 87.9 +/- 3.1% overall, 90.4 +/- 3.0% for single valve (aortic 88 +/- 5%, mitral 93.3 +/- 4%) replacement and 71 +/- 11% for multiple valve replacement. The actuarial rates of freedom from complications were as follows: endocarditis 95.7 +/- 1.8% (aortic 94 +/- 3.5%, mitral 100%), periprosthetic leak 98 +/- 1% (aortic 96.2 +/- 2.6%, mitral 100%), thromboembolism 95.2 +/- 2.3% (aortic 90.9 +/- 4.6%, mitral 96.7 +/- 3.3%), valve thrombosis 98.7 +/- 0.9% (aortic 100%, mitral 100%), anticoagulant-induced bleeding 90.3 +/- 2.6% and all valve-related complications 79.4 +/- 3.6% (aortic 78.8 +/- 3.6%, mitral 85.9 +/- 4.5%). The functional improvement in patients was very satisfactory and the risk of reoperation was 1.1% per patient-year. Over a 6 year time frame, the Omniscience valve has given excellent clinical performance.