St. Jude Medical Valve Research Articles

Comparative study between St. Jude Madical and bioprosthetic valves in the right side of the heart.

Comparative long-term performance characteristics of St. Jude Medical (SJM) and bioprosthetic valves were conducted retrospectively for patients who underwent prosthetic valve replacement in the right side of the heart from 1975 to 1988. Fifty-four patients received either SJM (n = 18) or bioprosthetic (n = 37) valves. The cumulative follow-up for SJM valves was 91 valves-years (range 3.9 to 7.2 years) and that for bioprostheses was 282 valve-years (range 1.3 to 14.8 years). Follow-up rate was 100%. The actuarial survival rate excluding hospital deaths at 5 years was 81 +/- 10% for SJM and 97 +/- 3% for bioprosthetic valve recipients (p = ns). The rates of freedom from thrombosis or anticoagulant-related hemorrhage, structural valve failure, prosthetic valve endocarditis, reoperation, and overall valve-related complications at 5 years were 72 +/- 11%, 100%, 100%, 83 +/- 9%, and 72 +/- 11% for SJM valve recipients, and 100%, 97 +/- 3%, 97 +/- 3%, 94 +/- 4%, and 94 +/- 4% for bioprosthetic valve recipients, respectively. Structural valve failure, prosthetic valve endocarditis and reoperations occurred at a similar incidence in each of the two types of prostheses. Thrombosis and overall valve-related events occurred more frequently in SJM valve recipients (5.5 +/- 2.5 vs 0%/valve-year; p less than 0.02, 6.6 +/- 2.7 vs 1.1 +/- 0.6 %/valve-year; p less than 0.03, respectively). The bioprosthetic valve which did not need warfarin anticoagulation therapy had low incidence of valve-related complications and showed good long-term durability even in the younger age group. The bioprosthetic valve was superior to the SJM valve in the right side of the heart.

Noise Level and Perception of the Closing Click After Heart Valve Replacement with St. Jude Medical and Björk Shiley Monostrut Prostheses

The metallic click generated by the closure of mechanical heart valve prostheses may severely bother patients, but generated sound energy and the extent of complaints after implantation are not known. In 62 patients, after valve replacement with St. Jude Medical (SJM) (n = 35) and Björk Shiley Monostrut (BSM) (n = 27) prostheses, sound energy was recorded with a calibrated noise level analyzer at 5, 10, and 100 cm distance from patients and correlated with their complaints. At a distance of 100 cm, the BSM valves produced a significantly higher sound pressure level, 30.5 +/- 5 db(A), compared to the SJM valves, 24.1 +/- 4 db(A) (p = 0.0001). There was no significant difference at shorter distances. After splitting into frequency bands the highest sound pressure levels were observed in the high frequency ranges (8 to 16 kHz) representing the metallic click. BSM valves produced higher sound levels in all frequency ranges at 1 m distance. Seventy-three percent of all patients were aware of the noise generated by the valve; 20% had disturbed sleep; and 26% preferred a less noisy valve type. Twelve of 27 patients with BSM valves wanted less noisy valves, whereas only 4 of 35 patients with SJM valves wished to have a less noisy valve type (Chi-square p = 0.003). In patients who could hear their valve measured, sound level was higher than in patients who could not. In 9 of 27 patients with BSM (33%), versus 3 of 35 with SJM prostheses (9%), the clicking caused sleep disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)

Rest and exercise hemodynamics of 20 to 23 mm allograft, Medtronic Intact (porcine), and St. Jude Medical valves in the aortic position

Doppler echocardiography was used to measure gradients and valve areas at rest and after supine bicycle exercise in 35 patients with valve replacements 20 to 23 mm in size. Thirteen patients with a St. Jude Medical valve (St. Jude Medical, Inc., St. Paul, Minn.) were matched to 13 patients with an allograft valve, and seven patients with a Medtronic Intact (porcine) valve (Medtronic, Inc., Minneapolis, Minn.) to seven patients with an allograft valve. Patients were matched for age, sex, valve size, body surface area, and left ventricular systolic function. There was no statistically significant difference between the matched groups for body surface areas, resting cardiac output, exercise heart rate, or workload achieved. Mean pressure gradient was higher for St. Jude Medical than for allograft groups, both at rest (11.8 +/- 6.67 mm Hg for St. Jude Medical versus 6.67 +/- 2.98 mm Hg for allografts) and after exercise (16.4 +/- 8.47 mm Hg versus 9.7 +/- 3.94 mm Hg), but the differences were of borderline significance (p = 0.016 and 0.027, respectively). Valve area at rest was similar for both devices (1.4 +/- 0.45 cm2 for St. Jude Medical versus 1.8 +/- 0.56 cm2 for allograft; p greater than 0.1). There were highly significant differences between patients with Intact and those with allograft valves for resting mean pressure gradient (19.3 +/- 4.23 mm Hg for Intact versus 5.9 +/- 3.68 mm Hg for allograft; p less than 0.001) and for exercise mean pressure gradient (27.8 +/- 8.63 mm Hg versus 8.1 +/- 8.43 mm Hg; p less than 0.001). The differences between the valve areas at rest also were significant (1.1 +/- 0.12 cm2 versus 2.2 +/- 0.62 cm2; p less than 0.01). It is concluded that when a tissue valve is indicated in patients with a small aortic root, the freehand allograft aortic valve is an ideal device from the hemodynamic perspective and is superior to the Intact valve. It is also probably superior in this respect to the St. Jude Medical valve, although the analysis may be biased slightly in favor of the allograft valve.

The central axis prosthetic cardiac valve: an in vitro study of pressure drop assessment under steady-state flow conditions

In this work, a new mechanical prosthetic heart valve, the central axis valve, is presented. This new prosthesis has been tested in vitro, and compared with four other common prosthetic cardiac valves (Starr-Edwards 6120, Bjork-Shiley monostrut, Medtronic-Hall, and St Jude Medical valves). All valves studied have the same orifice diameter of 22 mm. The prostheses were installed inside a transparent mitral test chamber, which enables pressure drop measurement to be made under steady-state flow conditions using a blood analogue fluid. Pressure drop loss is one important factor affecting the overall performance of a prosthetic heart valve. Steady-state flow tests are essential to predict certain flow characteristics and pressure gradient loss before more complicated, expensive, and difficult-to-interpret pulsatile flow tests are conducted. All experiments were performed in vitro and at steady volumetric flow rates of 10 to 30 l/min. The Starr-Edwards SE 6120 showed the highest values for pressure drop. The St Jude Medical valve offers the minimum resistance to flow. The central axis valve comes second to the Starr-Edwards valve for this type of measurement. The new valve is promising. A complete valve evaluation programme, covering initial conceptional design through to clinical use, is in progress. Materials for the fabrication of the new valve are also under consideration.

Analysis of Velocity in the Ascending Aorta in Humans.

To analyze velocity spectral energy distribution in humans, blood velocities were recorded by means of hot-film anemometry at 41 predetermined measurement points in the cross-sectional area of the ascending aorta approximately 6 cm downstream of the aortic valves. Measurements were made in 8 patients with normal aortic valves, in 4 after insertion of a St. Jude Medical (SJM) aortic valve and in 3 after insertion of a Starr-Edwards Silastic Ball (SSB) aortic valve. Data analysis based on Fast Fourier Transform demonstrated that turbulence energy was lower in patients with normal aortic valves than in patients after insertion of an artificial valve in the aortic position and probably more pronounced after SSB valves than after SJM valves. The spatial distribution of the turbulence energy above 100 Hz was more irregular than corresponding laminar velocities previously presented. The VER100 (Velocity Energy Ratio at 100 Hz, i.e. the velocity energy above 100 Hz divided by the total velocity energy) proved useful for evaluating differences in flow disturbances downstream of different aortic valves. The mean VER100 in the three categories of patients were respectively 0.3, 1.4, and 2.1%.

Turbulent stress measurements downstream of six mechanical aortic valves in a pulsatile flow model

In a pulsatile flow model aortic Björk-Shiley Standard, Convex-Concave and Monostrut valves were investigated together with the Hall-Kaster (Medtronic-Hall), St Jude Medical and Starr-Edwards Silastic Ball valve using hot-film anemometry. Three-dimensional visualization of average systolic Reynolds normal stresses (RNS) reflected the design of the valves. Mean average RNS were used for comparison of the fluid dynamic performance along with Velocity Energy Ratio (VER 100) and Turbulence Energy Ratio (TER) as a relative turbulence intensity for pulsatile flow. Mean average RNS ranged from 13.2 to 37.6 Nm −2 for all the valves with the highest levels for the Björk-Shiley Standard and Starr-Edwards Ball valve and lowest values for the St Jude Medical valve and with the Hall-Kaster (Medtronic-Hall), Björk-Shiley Convex-Concave and Monostrut valves in between.

Simultaneous implantation of St. Jude Medical aortic and mitral prostheses

Since January 1980, 92 consecutive patients received St. Jude Medical aortic and mitral prostheses simultaneously. Mean age was 57.6 years (standard deviation 12.4); 14 were 70 years or older. Twenty-three had a previous cardiac operation and 22 had additional procedures performed at the time of double valve replacement. Before the operation 62% of the patients were in New York Heart Association functional class III and 29% were in class IV or required emergency operation. There were six (6.5%) deaths within 30 days. None of the hospital deaths were valve related; all occurred in patients who had additional risk concerns. Follow-up is 100% complete and ranges from 2 to 80 months, totaling 242 patient-years (mean 33.8 months). All except four hospital survivors reached class I or II and 40 patients (47%) remain asymptomatic. The actuarial survival rates are 82% at 1 year, 70% at 3 years, and 60% at 5 years. Causes of late death include heart failure (10), sudden, unexplained death (five), reoperation for coronary artery disease (one), noncardiac (four), and valve related (five). The linearized rate of fatal valve-related events is 2.1% pt-yr. A total of 22 valve-related complications (including five fatal) occurred is 18 patients, for a linearized rate or incidence of 9.1%/pt-yr. Eleven thromboembolic episodes (rate 4.6%/pt-yr) occurred in nine patients; three of these (1.2%/pt-yr) were fatal. Thromboembolic and bleeding complications represented 64% of all valve-related complications. Four patients had six episodes of prosthetic valve endocarditis (incidence 2.5%/pt-yr), of which one (incidence 0.4%/pt-yr) was fatal. Paravalvular leak contributed to the fifth valve-related death. At 5 years, 83% of patients were free of thromboembolic complications; 94% were free of anticoagulant-related hemorrhage; and 71% were free of all valve-related complications. There are few comparable data for patients who have had simultaneous replacement of aortic and mitral valves with other mechanical prostheses. The total incidence of valve-related complications for patients with bioprostheses ranges between 3.9%/pt-yr and 10.4%/pt-yr and is similar to the 9.1%/pt-yr observed in the present series. The type of valve-related complication (thromboemboli and bleeding versus valve deterioration) is the principal difference between St. Jude Medical and bioprosthetic valves in patients who require simultaneous replacement of aortic and mitral valves.

Comparative study of warfarin versus antiplatelet therapy in patients with a St. Jude Medical valve in the aortic position

To determine the necessity of long-term warfarin anticoagulation after St. Jude Medical aortic valve replacement in adults, we evaluated the risks of thromboembolism, valve thrombosis, anticoagulant hemorrhage, and sudden cardiac death in two groups of patients. Group I consisted of 41 patients treated with conventional long-term warfarin therapy. Forty-two patients in Group II were treated primarily with antiplatelet therapy (aspirin, dipyridamole, or both); 17 of these patients received warfarin for a short time postoperatively and seven others received it intermittently during the study period. The groups were similar with respect to age, sex, associated cardiovascular disease, and length of follow-up (mean 29 months per patient). In the warfarin-treated group, three late sudden deaths occurred, one of which was preceded by a cerebrovascular accident, for a cardiac mortality of 2.7% per patient-year. There were eight major nonfatal complications (7.3% per patient-year), of which four were hemorrhagic and four embolic. In Group II, there was one sudden cardiac death (1.1% per patient-year) and four major complications occurred (3.2% per patient-year). Two of the complications were embolic and two were episodes of valve thrombosis, both necessitating reoperation. Although the incidence of serious morbidity in the warfarin-treated group was twice that of patients treated with antiplatelet therapy, there were no statistically significant differences in the rates of sudden death or major complications. These data suggest that antiplatelet therapy may be as effective as warfarin in preventing embolism from the St. Jude Medical valve in the aortic position. Valve thrombosis occurred in two patients, both receiving antiplatelet therapy (2.2% per patient-year). Whether this type of valve failure can be prevented by warfarin remains in question.

Five-year clinical evaluation of the St. Jude Medical valve prosthesis in 136 patients.

One hundred and thirty-six patients (June 1979, through May 1984) underwent mitral, aortic or double valve replacement and apico-aortic bypass with the St. Jude Medical (SJM) prosthesis, at Ryukyu University Hospital, Okinawa. Operative mortality for the entire group was 4.4 per cent. Late mortality from 1979-1984 was 6.1 per cent. There were no deaths related to mechanical failure. Warfarin anticoagulation was recommended for all patients. The incidence of thromboembolism was 0.76/100 patient years. Post operative catheterization studies in 21 patients one year after operation showed a satisfactory recovery of cardiac function. The SJM valve seems to be the satisfactory artificial valve in present use.

Mitral valve replacement with St Jude Medical prosthesis. Incidence of thromboembolic events in 349 patients.

This study reports incidence of thromboembolic episodes in a series of 349 patients where the St. Jude Medical (SJM) valve was implanted in the mitral position (252 isolated mitral, 91 mitral and aortic, 4 triple valve and 2 mitral and tricuspid valve replacements). The mean follow up was 28 months (range 6 to 57 months) which represents 784 patient-years. Overall operative mortality was 15 patients (4.3%). There were no valve-related deaths. Late post-operative prosthetic thrombosis occurred in 3 poorly anticoagulated patients (0.4% patient-years). A further 4 patients had a thromboembolic episode (0.5% patient-years). The overall frequency of thromboembolic episodes was 0.9 events per 100 patient-years. Per- and post-operative anticoagulation methods are described. The frequency of thromboembolism was studied with respect to the performance of SJM valve analyzed by echocardiography regardless the positioning of the prosthesis in the mitral ring. Our experience indicates that the SJM valve offers an excellent alternative in the choice of mechanical valve.

Enlargement of the narrow aortic root and oblique insertion of a St Jude prosthesis.

The aortic root was enlarged and a St Jude Medical valve obliquely inserted in 11 patients. Prosthetic valve sizes at least one, but often two, sizes larger than that which would normally be accommodated by the dimensions of the host aortic annulus were used. Closure of the valve was not affected by obliquity. This simple technique is recommended whenever the host aortic annulus does not allow the insertion of a substitute valve of an appropriate size.

THE ST JUDE MEDICAL VALVE—THE AUSTRALIAN EXPERIENCE

Since October, 1978, 181 St Jude medical cardiac valves have been implanted in 166 patients throughout Australia. There were 152 single implants, 13 combined mitral and aortic valve implants, and one triple valve implant. Hospital mortality rates were similar to those for all types of prosthetic cardiac valves. Thromboembolic complications occurred less frequently in the patients with St Jude valves than in reports of similar patients with other prostheses, provided that anticoagulation was maintained.