The Monostrut Björk-Shiley valve

Thirty-year results after implantation of the Björk-Shiley Convexo-Concave Heart valve prosthesis

BACKGROUND

Modifications of the Björk-Shiley valve prosthesis have shown good long-term results. The convexo-concave model, however, was recalled 27 years ago because of a propensity for breakage due to outlet strut fracture. The objective of this study is to describe the 30-year outcome after implantation of the Björk-Shiley convexo-concave mechanical heart valve prosthesis (Pfizer, Rye Brook, NY).

METHODS

The study included 279 patients who were operated between 1979 and 1983 at Turku University Hospital. A total of 305 valves were implanted; 205 in the aortic position and 100 in the mitral position. Patient records were reviewed for baseline characteristics and late events, data on mortality were acquired from registries.

RESULTS

Mean actuarial survival was 19.8 years and mean follow-up was 19.2 years (maximum 34 years). Freedom from reoperation was 91.3% at 30 years. There were 3 outlet strut fractures (2 fatal) during follow-up. Statistically significant predictors of mortality were age and concomitant coronary artery bypass grafting.

CONCLUSIONS

Despite the possibility of structural valve failure the Björk-Shiley convexo-concave valve confers excellent 30-year survival.

Mechanical heart valve prostheses:

Mechanical heart value prostheses have been in use since the 1950s. Many prostheses have been used for a while and then discontinued. Today, there are a large number and variety of prostheses in use and an even larger variety that are in place in patients. These may be explanted at any time for a number of reasons. It is essential for the practicing pathologist to be able to identify the prosthesis and be aware of some of its reported complications and modes of failure. This article, and a second one on bioprosthetic heart valves, is designed as a ready reference guide to heart valve prostheses, their important identifying features, their common complications, and modes of failure. It should help in the accurate identification of explanted prosthetic valves and more definitive reports. This accuracy of identification as well as tracking of abnormalities noted will, we hope, permit the identification of new failure modes and the recording of causes of failure of new (or even modified) prosthetic heart valves.

Ministernotomy versus median sternotomy for aortic valve replacement: a prospective, randomized study

BACKGROUND

Minimally invasive aortic valve replacement reduces surgical trauma and, supposedly, postoperative pain, blood loss, and length of stay. A prospective, randomized study was designed to prove these theoretical advantages.

METHODS

Forty patients undergoing isolated, elective aortic valve replacement were randomized into two equal groups. Patients in group M underwent aortic valve replacement through a ministernotomy (reversed L or reversed C). In group S, a median sternotomy was used. The anesthetic and surgical protocol was identical for both groups. Pain was evaluated on a daily basis. Pulmonary function tests were performed preoperatively and before hospital discharge in all patients.

RESULTS

There were two deaths in each group. Cross-clamp time was longer in group M: 70 +/- 19 minutes versus 51 +/- 13 minutes in group S (p = 0.005). There were no statistically significant differences between groups M and S in pump time (95 +/- 20 minutes versus 83 +/- 19 minutes), extubation time (9.9 hours in both groups), chest drainage (479 +/- 274 mL/L 24 hours versus 355 +/- 159 mL/24 hours), transfusion requirements (27% in both groups), pain evaluation (1.34 +/- 1.3 versus 2.15 +/- 1.5), length of stay (6.2 +/- 2.3 days versus 6.3 +/- 2.5 days), and cosmetic appraisal. Forced vital capacity decreased 26% from preoperative reference values in group M and 33% in group S (p = not significant). Forced expiratory volume in 1 second decreased 22% and 35%, respectively (p = not significant).

CONCLUSIONS

This study has failed to prove the theoretical advantages of minimally invasive aortic valve replacement. With this technique, cross-clamp time is longer than with a median sternotomy.

Management of Nonobstructive Thrombosis of Prosthetic Mitral Valve in Asymptomatic Patients in the Early Postoperative Period: A Study in 20 Patients

The purpose of the present study was to determine the optimal management of nonobstructive thrombi in the early postoperative period after mitral valve replacement.Twenty cases of early thrombi were revealed by systematic transesophageal echocardiography (TEE) performed 9 days after surgical implantation of 229 St. Jude prostheses. Patients were prospectively randomized into two groups: the first group received oral anticoagulants (fluindione), and the second group was treated with a combination of oral anticoagulants and aspirin. The impact of the different therapies on prosthetic thrombi was assessed by systematic TEE at 5 months. All thrombi were nonobstructive and disappeared without fibrinolytic agents or surgery. Seven large (>/= 5 mm) thrombi disappeared: in two patients after reintroduction of intravenous heparin and in five patients with an optimized oral treatment (anticoagulants alone in one patient, anticoagulants associated with aspirin in four patients). In the 13 small (< 5 mm) thrombi, 11 disappeared with an optimized oral treatment: anticoagulants alone in nine patients and anticoagulants associated with aspirin in two patients. The other two small thrombi treated with heparin alone initially persisted and finally disappeared with heparin associated with aspirin. In the group with large thrombi, we recorded a 43% rate of thromboembolic events, with more deaths and severe cerebral embolic events than in the patients with small thrombi. Embolic events were associated with mobile thrombi. An optimized oral anticoagulation therapy with correction of the parameters of Virchow et al. is effective in the treatment of small prosthetic thrombi. For large thrombi, the high rate of thromboembolic events would appear to require a more aggressive approach such as an association of heparin with aspirin and TEE follow-up.

The Spanish Monostrut Study Group: a ten-year experience with 8,599 implants

BACKGROUND

The Monostrut valve is a pyrolytic carbon, tilting-disc prosthesis with no welds. After the first implantation in Spain in May 1983, the Spanish Monostrut Study Group was established to evaluate prospectively the performance of the valve using uniform protocols.

METHODS

During a 10-year period, 8,599 Monostrut valves were implanted in 7,317 patients in 22 centers. Mean age was 53.3 +/- 11 years. Of the total group, 3,229 underwent aortic valve replacement, 2,806 had mitral valve replacement, and 1,282 had double valve replacement. Follow-up was 96% complete, with a mean period of 4.3 years and a total of 29,155 patient-years.

RESULTS

The operative mortality rate was 7.2%. The 10-year probability of freedom from valve-related complications and linearized rates (event/100 patient-years in parentheses) were as follows: structural deterioration, 100% (0); nonstructural dysfunction, 96% +/- 0.5% (0.51); thromboembolism, 82.9% +/- 1.5% (1.32); anticoagulant-related hemorrhage, 87.6% +/- 1.4% (0.98); and prosthetic valve endocarditis, 96.1% +/- 0.5% (0.48). There were five obstructive valve thromboses (0.017/100 patient-years). Actuarial freedom from reoperation was 95% +/- 0.5% at 10 years. Actuarial freedom from all valve-related morbidity was 70.2% +/- 1.6%; freedom from all valve-related morbidity and mortality (including operative and sudden deaths) was 62.6% +/- 2% (70.1% +/- 2% for aortic valve replacement, 56.9% +/- 2% for mitral valve replacement, and 59.8% +/- 3% for double valve replacement; p < 0.0001). Clinically, 5,988 patients (94%) are in New York Heart Association class I-II.

CONCLUSIONS

The Monostrut valve has shown no structural failures and a low rate of valve-related complications over a 10-year period in a large patient population.

The CarboMedics valve: midterm follow-up with analysis of risk factors

BACKGROUND

This study examined the midterm results with the CarboMedics prosthetic valve.

METHODS

From 1987 through 1991 a total of 569 patients received the CarboMedics prosthesis.

RESULTS

Early mortality was 4.9% and related to emergency operation, presence of diabetes mellitus, coronary artery disease, preoperative New York Heart Association class, duration of cardiopulmonary bypass, and aortic cross-clamp time. Midterm follow-up with respect to mortality was 100% complete. All patients were followed up in the hospital after 1 year. In addition 86% of the patients responded to a questionnaire. Mean follow-up was 3 years (range, 0 to 5.6 years). Cumulative survival at 1 and 4 years was 91.2% +/- 1.2% and 83.7% +/- 1.8%, respectively. Five patients experienced obstructive valve thrombosis (0.3%/patient-year), 16 patients had major thromboembolic events (0.9%/patient-year), and 10 patients had major warfarin-related bleeding (0.6%/patient-year) requiring hospitalization or blood transfusions. Eight patients were reoperated on for paraprosthetic leak (0.4%/patient-year). Prosthetic valve endocarditis developed in 4 patients (0.2%/patient-year). No structural valve failure was observed.

CONCLUSIONS

Midterm follow-up demonstrates that the CarboMedics mechanical prosthesis is reliable and has an acceptable rate of valve-related complications.

Doppler-derived gradients in normally functioning Monostrut Björk-Shiley prostheses

In summary, reference values of Doppler gradients obtained in a large number of patients with normal-functioning mitral and aortic Monostrut Björk-Shiley prostheses are reported. It is shown that the value of the transprosthetic gradient increases with decreasing valve size in patients with aortic prostheses. No individual significant variations of the transprothetic Doppler gradient during a 3-year follow-up were observed.

Clinical and hemodynamic performance of the 19-mm Carpentier-Edwards porcine bioprosthesis

Because of concerns about the hemodynamic performance of 19-mm porcine valves, we retrospectively reviewed the clinical results and echocardiographic studies of 52 consecutive patients who received a 19-mm Carpentier-Edwards porcine bioprosthesis (model 2625) for aortic valve replacement from 1986 through 1991. Nearly 87% of the patients were women, the mean age was 69 years, and the mean body surface area was 1.63 +/- 0.27 m2. Seventy-three percent of the patients had pure aortic stenosis, 96% were in New York Heart Association classes III and IV, and 56% underwent urgent or emergent operation. Overall hospital mortality was 7.7% with a late mortality of 8.3% at a mean follow-up of 25 +/- 18 months. No patient experienced a valve-related complication, and 95% of surviving patients were in New York Heart Association classes I and II. Two-dimensional and Doppler echocardiography performed during the first postoperative week revealed a maximal instantaneous gradient of 44.7 +/- 13.0 mm Hg. In 43 patients for whom additional data were available, the mean gradient was 26.4 +/- 8.2 mm Hg with an effective orifice area of 0.85 +/- 0.18 cm2. This study defines the normal range of postoperative gradients across the 19-mm Carpentier-Edwards porcine valve and demonstrates that patients receiving this valve can achieve significant clinical improvement despite the presence of high transvalvular gradients measured by echocardiography.