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Biomedical subjects

G F Tyers

Publications and source records attributed to G F Tyers.

At least 37 records · Page 2Linked to original sources
PubMed1995

Medtronic Intact porcine bioprosthesis: clinical performance to seven years.

The clinical performance of the Medtronic Intact porcine bioprosthesis was evaluated in 1,084 patients (mean age 66.4 years, range 9 to 91 years) who had a total of 1,099 implantations between 1985 and 1992, inclusive. There were 709 aortic valve replacements, 297 mitral valve replacements, and 80 multiple valve replacements. Concomitant procedures were performed in 432 (39.3%). The age group distribution (years) was 35 or younger in 20 patients, 36 to 50 in 64, 51 to 64 in 274, 65 to 69 in 225, 70 or older in 500. The total follow-up time was 2,741 patient-years (mean, 2.5 years) and was 97.5% complete. The early mortality rate was 7.1% and late mortality was 3.9% per patient-year. The overall patient survival at 7 years was 70% +/- 3%. The freedom from major thromboembolism was 94% +/- 1% at 7 years (p = not significant for valve positions). The freedom from reoperation at 7 years was 93% +/- 1%; freedom from valve-related mortality was 89% +/- 2%. The freedom from structural valve deterioration at 7 years was 97% +/- 1% (aortic valve replacement 97% +/- 1%; mitral valve replacement 97% +/- 2%). The freedom from structural valve deterioration among age groups was not different for the overall population, aortic valve replacement, or mitral valve replacement. Hemodynamic assessment revealed obstructive properties for aortic valve replacement sizes of 21 and 23 mm and for mitral valve replacement sizes of 25 and 27 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1995

Tricuspid valve replacement: porcine bioprostheses and mechanical prostheses.

The clinical performance of tricuspid valve replacement with bioprostheses and mechanical prostheses was assessed in a series of 5,489 total valve replacement operations performed from 1975 to 1992. There were 97 (1.8%) tricuspid valve replacements in 94 patients (16 men, 78 women) with a mean age of 55.4 +/- 13.8 years. Bioprostheses (mean patient age, 55.9 +/- 14.1 years) were used in 83 operations and mechanical prostheses (mean patient age, 52.1 +/- 11.9 years) were used in 14 operations. There were 30 isolated tricuspid valve replacements and 67 tricuspid valve replacements incorporated in multiple valve replacements. The total cumulative follow-up was 360 patient-years (bioprostheses, 321 years; mechanical prostheses, 39 years) (96.8% complete). The mean follow-up was 3.7 years (bioprostheses, 3.9 years; mechanical prostheses, 2.8 years) (p = not significant). The early mortality was 14.4% (bioprostheses, 14.5%; mechanical prostheses, 14.3%) (p = not significant) (isolated replacement, 13.3%; multiple replacement, 14.9%). The late mortality was 9.2% per patient-year (isolated replacement, 12.2% per patient-year; multiple replacement, 7.9% per patient-year). The freedom from structural valve deterioration at 5 and 7 years was 100% for mechanical prostheses and 97.1% +/- 2.9% for bioprostheses (p = not significant). For isolated tricuspid valve replacement, the freedom from structural valve deterioration for bioprostheses was 90.9% +/- 8.7% at 5 years and at 7 years (p = not significant). For the mechanical prostheses, the freedom was 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1995

Carpentier-Edwards supraannular porcine bioprosthesis: clinical performance to twelve years.

The Carpentier-Edwards supraannular porcine bioprosthesis, a second-generation biologic prosthesis, has had clinical performance assessment to 12 years. This bioprosthesis was used in 2,489 operations in 2,444 patients between 1982 and 1992, inclusive (mean age 64.1 years, age range 6 to 89 years). There were 1,335 aortic valve replacements (AVR), 938 mitral valve replacements (MVR), and 200 multiple valve replacements (MR). Concomitant procedures were performed in 1,017 cases (40.9%). The age group distribution was: 35 years or younger, 83 patients; 36 to 50 years, 245; 51 to 64 years, 728; 65 to 69 years, 458; and 70 years and older, 975. The total follow-up was 12,785 patient-years (mean, 5.1 years) and was 96% complete. The early mortality rate was 7.4% (185 patients), and the late mortality was 4.9%/patient year (623). Concomitant procedures influenced both early and late mortality (p < 0.05). The overall patient survival at 12 years was 44% +/- 3% (p < 0.05, AVR > MVR, MR). The freedom from thromboembolism was not different by valve position. The freedom from major thromboembolism at 12 years was 82% +/- 4% (p = not significant by valve position). The overall freedom from antithromboembolic hemorrhage was 96% +/- 1% at 12 years (p < 0.05, AVR > MVR > MR). The overall freedom from valve-related reoperation at 12 years was 58% +/- 5% (p < 0.05, AVR > MVR, MR), and from valve-related mortality 89% +/- 2% (p < 0.05, AVR > MVR > MR). The freedom from residual morbidity (permanent impairment) at 12 years was 87% +/- 4% (p = not significant by valve position).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Reoperation in biological and mechanical valve populations: fate of the reoperative patient.

From 1975 through 1992 inclusive, reoperative valve replacement (REOP) was required by 12.9% of patients (708/5,499). Of 1,355 patients with mechanical prostheses (MP), 46 (3.4%) came to REOP versus 662 of 4,144 patients (16%) with biological prostheses (BP). Early REOP mortality rate was 17.4% (8/46) for MP and 10.6% (70/662) for BP (p = not significant). It was higher with age greater than 75 years (p < 0.05) and trended higher with concomitant procedures and with increasing number of REOPs (p = not significant). The percentage freedom from REOP at 5 and 10 years for all BP was 96.0% +/- 0.4% and 74.9% +/- 1.1% compared with 93.6% +/- 1.2% and 87.9% +/- 2.5% for MP. The most common cause of REOP in the BP patients was structural valve deterioration, which was uncommon in patients with MP (72% versus 2% of REOP but only 15% versus 0.1% of initial implants). Nonstructural dysfunction was the leading cause of REOP in the MP group (65% versus 11%). Prosthetic valve endocarditis (18% versus 10%) and thromboembolic complications (10% versus 1%) were also more frequent causes of REOP in MP patients. However, the increased relative role of these factors with MP is due to the minimal incidence of structural valve deterioration. When related to the original choice of MP versus BP, only thromboembolic complication (3.8 times) was more prevalent as a cause of REOP in patients receiving MP at their previous procedure (p = not significant). For patients who previously received BP, structural valve deterioration (69 times) was more likely to lead to REOP than with MP (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1995

Clinical performance of biological and mechanical prostheses.

Prosthetic valve replacement remains the most viable alternative for the treatment of severely diseased heart valves. The cumulative experience of mechanical protheses and bioprostheses was evaluated for a 10-year performance comparison: Carpentier-Edwards standard porcine bioprosthesis (CE-S), 1,214 operations; Carpentier-Edwards supraannular porcine bioprosthesis (CE-SAV), 2,489; and mechanical prostheses, 1,364 operations (St. Jude Medical, Carbomedics, Duromedics, and Björk-Shiley Monostrut). The freedom from thromboembolism and hemorrhage at 10 years was 82% for CE-S, 78% for CE-SAV, and 65% for mechanical prostheses (p < 0.05). The relationship existed for major thromboembolism and hemorrhage, 91% (CE-S), 87% (CE-SAV), and 88% (mechanical) (p < 0.05), without clinical relevance. The freedom from structural valve deterioration and valve-related reoperation favored mechanical prostheses (p < 0.05) at 10 years (structural failure: 78% for CE-S, 81% for CE-SAV, and 99% for the mechanical group; reoperation: 74% for CE-S, 76% for CE-SAV, and 88% for mechanical prostheses). The freedom from fatal reoperation was not clinically different: 96% for CE-S, 99% for CE-SAV, and 99% for mechanical prostheses (p < 0.05) at 10 years. The freedom from valve-related mortality was not different (p = not significant) at 10 years: 87% for CE-S; 92% for CE-SAV; and 91% for mechanical. The freedom from permanent impairment or residual morbidity, primarily from thromboembolism, was 95% for CE-S, 92% for CE-SAV, and 95% for mechanical group (p < 0.05) but not clinically relevant.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1995

Carpentier-Edwards standard porcine bioprosthesis: clinical performance to seventeen years.

BACKGROUND: The role of porcine bioprostheses in cardiac valve replacement has been under review for several years. The literature deals primarily with age as a determinant of durability, as well as the intermediate-term performance of various prostheses. The performance of the Carpentier-Edwards first-generation standard porcine bioprosthesis is presented over the long-term with further documentation on age determinants. METHODS: The "Guidelines for Reporting Morbidity and Mortality After Cardiac Valvular Operations" were used for definitions of valve-related complications, categorization, and statistical methods. The valve-related complications were evaluated in a time-related manner by actuarial life-table techniques. The Lee-Desu statistic test was used for comparison of performance by valve positions and age groups. Hazard function rates were demonstrated for complications and composites. RESULTS: Of the Carpentier-Edwards porcine bioprostheses implanted in 1,195 patients (1,214 operations, 1,315 valves) commencing in 1975 the early mortality was 7.6% (92). The early mortality without concomitant procedures was 6.1% and with 11.7%. The late mortality was 5.3% per patient-year; 4.6% patient-year without and 7.5% per patient-year with concomitant procedures. The valve-related causes of late mortality (131) were thromboembolism (41), antithromboembolic hemorrhage (14), prosthetic valve endocarditis (20), nonstructural dysfunction (12), and structural valve deterioration (44). The valve-related deaths (early, 7; late, 124) were 21.2% of the total 617 total deaths. Reoperation for valve-related complications was performed in 406 patients (4.1% per patient-year), of which 327 were for structural valve deterioration (3.3% per patient-year). Mortality for reoperation was 0.5% per patient-year (49 patients) or 12.1%. Of the 49 deaths, 33 were caused by structural valve deterioration. The linearized occurrence rate for thromboembolism was 1.6% per patient-year (major, 0.9% per patient-year, and minor, 0.7% per patient-year). The fatal thromboembolic rate was 0.4% per patient-year (41), undifferentiated by valve position. The freedom from thromboembolism was 76% at 17 years (p = not significant by valve position) (major, 87%; fatal, 93%). The freedom from prosthetic valve endocarditis was 92% at 17 years (p = not significant by valve position). The freedom from reoperation, at 15 years, was 38%: aortic (AVR), 55%; mitral (MVR), 20%; and multiple valve replacement (MR), 24% (p < 0.05 AVR > MVR, MR). The freedom from structural valve deterioration, at 15 years, was 41%; AVR, 58%; MVR, 21%; MR, 36% (p < 0.05 AVR > MVR, MR). The freedom from structural valve deterioration was greater for advancing age groups (p < 0.05); AVR > or = 70 years 96% at 12 years, and 65 to 69 years 94% at 12 years and 82% at 15 years; MVR > or = 70 years 85% at 12 years, and 65 to 69 years 54% at 12 years. The freedom from valve-related mortality was 73% at 17 years: AVR, 80%; ; MVR, 61%; and MR, 67% (p < 0.05 AVR > MVR, MR). The freedom valve-related residual morbidity was 94% (p = not significant by valve position). CONCLUSIONS: The Carpentier-Edwards standard porcine bioprosthesis continues to provide satisfactory clinical performance to 17 years. Thromboembolism is a more serious problem than structural failure: 92 major thromboembolic events with 41 fatalities compared with 44 fatalities of which 33 occurred with reoperation. The prosthesis is especially recommended for patients more than 65 years of age for AVR and more than 70 years of age for MVR.

Adult↗
PubMed1994

The Medtronic Intact porcine bioprosthesis: clinical performance to eight years.

The Medtronic Intact porcine bioprosthesis was implanted in 274 patients, in 278 operations, between 1984 and 1992 inclusive. Of the total patient population, 171 patients had 175 aortic valve replacements (AVR), 75 had mitral valve replacement (MVR), two had tricuspid valve replacement and 26 had multiple valve replacement (MR). Concomitant procedures, primarily coronary artery bypass, was performed in 97 (34.9%). The follow up was 98.2% complete; total follow up was 758 patient-years, mean 2.8 years. The early mortality was 6.5% (18 patients) and the late mortality 4.0% per patient-year (30 patients). Of the late deaths, 10 were valve-related-thromboembolism (n = 2), anticoagulant-related hemorrhage (n = 1), prosthetic valve endocarditis (n = 4), non-structural dysfunction (n = 2), and structural valve deterioration (n = 1). Only one death occurred as a consequence of reoperation. The freedom from thromboembolism at six and eight years was-overall 86 +/- 4%; major 96 +/- 1%; fatal 99 +/- 1%. The overall linearized rate of thromboembolism was 3.0% per patient-year. The freedom from anticoagulant-related hemorrhage was 93 +/- 3%; non-structural dysfunction 87 +/- 9%; and structural valve deterioration 97 +/- 2% (AVR 97 +/- 2% at six and eight years, MVR 100% at six years). The freedom from SVD by age groups was- < or = 35 years 100%; 36-50 years 94 +/- 6%; 51-65 years 98 +/- 2%; and > or = 65 years 97 +/- 2% (p = NS). The freedom from valve-related mortality at six and eight years was 86 +/- 8%; residual morbidity 96 +/- 1%; and reoperation 91 +/- 3%. The Medtronic Intact, zero-pressure glutaraldehyde fixed prosthesis requires continued long term assessment to determine if the low incidence of structural valve deterioration is maintained.

Adult↗
PubMed1994

Carpentier-Edwards standard and supra-annular porcine bioprostheses: 10 year comparison of structural valve deterioration.

From 1975 to 1986 the Carpentier-Edwards standard (CE-S) and supra-annular (CE-SAV) porcine bioprostheses were implanted in 1213 and 1000 patients, respectively. The mean age of the standard group was 57.6 years (range 8 to 85 years) while in the supra-annular group it was 60.7 years (range 13 to 85 years). The freedom from structural valve deterioration (SVD) at 10 years for the entire patient population was 79.4% +/- 3.1% with CE-SAV and 76.1% +/- 1.6% with CE-S (p < 0.05). The overall freedom from SVD for those patients undergoing mitral valve replacement (MVR) was 74.5% +/- 4.6% for CE-SAV and 68.7% +/- 2.8% for CE-S (p = NS), while for those undergoing aortic valve replacement (AVR) it was 86.5% +/- 4.3% for CE-SAV and 84.1% +/- 2.0% for CE-S (p = NS). In those patients under 35 years of age undergoing MVR, the freedom from SVD for CE-SAV and CE-S was 94.4% +/- 5.4% and 62.9% +/- 8.6%, respectively (p < 0.05 at 8 years); for those aged 36-50 years, it was 75.6% +/- 7.4% and 61.7% +/- 6.0%; for those aged 51-65 years, it was 76.2% +/- 7.4% and 69.6% +/- 4.2%; for those over 65 years, it was 74.1% +/- 7.1% and 82.2% +/- 5.2%; for those aged 65-69 years, it was 70.2% +/- 8.7% and 63.7% +/- 8.1%; and for those over 70 years of age, it was 79.2% +/- 8.7% and 95.3% +/- 3.2%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Analysis of set screw and side-lock connector reliability.

A retrospective review of complications with connectors and lead-to-header interfaces was performed following 649 pacing procedures between 1980 and 1990. There were 88 lead revisions (13.6%), 81 device replacements or modifications (12.5%), and 480 new implants (74%) using devices of five manufacturers. Two basic connector types were studied, one utilizing a set screw and the other using a side-lock compression fitting. The set screw makes electrical contact and mechanically secures the lead connector pin with a set screw insulated by a self-sealing grommet or an integral or separate set screw cover. The side-lock makes electrical contact with an automatic spring mechanism while the plastic lead terminal is secured in the connector block of the pacemaker by a Delrin side-lock compression fitting. Four hundred fifty-nine set screw connector devices were followed for up to 12 years with 14 complications (3.1%) whereas 82 side-lock connector devices were followed for up to 5 years with one complication (1.2%). The set screw and side-lock connectors were reliable over the period of follow-up. Although the complication rate appeared lower with the side-lock, follow-up was shorter and the number of implants smaller. With the leads used in this study, the side-lock proved to be a desirable feature due to simplicity, speed, safety, and ease of use. One limitation is the requirement for a precise IS-1 connector terminal diameter.

Electrodes, Implanted↗
PubMed1991

Pregnancy and childbearing in a population with biologic valvular prostheses.

Long-term performance of biological prostheses and course of pregnancy, labor, and delivery were evaluated in women less than 35 years of age. Between 1975 and 1987, 87 female patients received a porcine (n = 86) or pericardial valve (n = 1); the mean patient age was 26.8 years, with a range of 8 to 35 years. A total of 17 of these patients experienced 37 pregnancies. A total of 25 babies were delivered, of which 19 were babies of normal birth weight born at term and six were born prematurely (two of these were stillborn). There were six spontaneous abortions and five therapeutic abortions. The mean time from primary operation to first delivery was 29 months. Of the 17 pregnant patients, 14 were in normal sinus rhythm and three were in atrial fibrillation. One of those in fibrillation had a therapeutic abortion while receiving warfarin therapy, and another was successfully delivered of her neonate after 7 months of warfarin therapy. The remaining 15 patients were treated through 35 pregnancies without anticoagulants or antiplatelet agents. Of the total population of 87 patients, 32 (36.8%) were treated for valve-related complications. Structural valve deterioration occurred in eight patients (47.1%) of the pregnancy group and 10 patients (14.3%) of the nonpregnancy group (p less than 0.05). The freedom from structural valve deterioration at 10 years was 23.3% +/- 14% for the pregnancy group and 74.2% +/- 8.5% for the nonpregnancy group (p less than 0.05, age as a determinant, p not significant). There were eight valve-related deaths (1.5%/patient-year). Reoperation was performed in 59% of the pregnancy group and 19% of the nonpregnancy group, primarily for structural valve deterioration manifested as valvular obstruction from aggressive calcification (p less than 0.05). The freedom from reoperation at 10 years parallels freedom from structural valve deterioration (20.3% +/- 12.4% and 64.3 +/- 9.1% for the pregnancy and nonpregnancy groups, respectively, with p less than 0.05; with age added as a determinant, p not significant). The overall reoperative mortality was 8.7% (two patients). The biologic prostheses afforded successful pregnancy without fetal wastage or congenital anomalies and without significant maternal morbidity or mortality.

Adult↗
PubMed1991

Carpentier-Edwards porcine bioprostheses. Comparison of standard and supra-annular prostheses at 7 years.

The performance of the Carpentier-Edwards supra-annular (CE-SAV) porcine bioprosthesis is compared with the Carpentier-Edwards standard (CE-S) porcine bioprosthesis at 7 years. The standard prosthesis was implanted in 1,195 patients between 1975 and 1987, while the supra-annular prosthesis was implanted in 1,956 patients between 1982 and 1989. The total follow-up for the standard prosthesis was 8,850 patient-years with a mean follow-up of 7.4 years, while for the supra-annular prosthesis it was 7,317 years with a mean of 3.7 years. The follow-up for the standard prosthesis was 96.7% and for the supra-annular prosthesis was 97.6%. The freedom from structural valve deterioration (SVD) for aortic replacements is 96.1 +/- 0.9% for CE-S and 97.6 +/- 1.4% for CE-SAV at 7 years (p = NS). The freedom for mitral replacements from SVD is 89.1 +/- 1.7% and 88.6 +/- 2.8%, respectively, for CE-S and CE-SAV (p = NS). The freedom for multiple replacements at 7 years was 80.0 +/- 4.5% for CE-S and 97.8 +/- 1.5% for CE-SAV (p less than or equal to 0.05). The freedom from SVD for the age group equal to or less than 35 years is 79.0 +/- 4.7% for CE-S and 85.0 +/- 9.4% for CE-SAV (p = NS). The freedom for the age group 36-50 years is 85.2 +/- 2.8% and 90.4 +/- 4.5%, respectively, at seven years for the CE-S and CE-SAV prostheses (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1991

Traumatic rupture of the thoracic aorta. A 20-year review: 1969-1989.

Acute traumatic injury of the thoracic aorta is a relatively common injury of deceleration accidents, usually high-speed motor vehicle accidents. The limiting factor to successful hospital management of these victims is early diagnosis and prompt treatment. Between the years 1969 and 1989, 116 patients (87 men and 29 women) were diagnosed with acute traumatic injury of the aorta. The mean age was 38.8 years, and the range was from 11 to 82 years. All patients who presented to the hospital emergency departments were included in the evaluation. The diagnosis of aortic rupture was firmly established by either aortography, surgery, or autopsy. The site of injury in 105 (90.5%) was the aortic isthmus, that is, distal to the origin of the left subclavian artery. In nine patients (7.7%) the injury was in the distal thoracic aorta. Two patients had injuries of the aortic arch. Associated injuries were present in 110 patients (95%); 16 patients (14%) had no external evidence of chest injury. Only 50 patients (43%) had the opportunity for definitive surgical management. The nonsurgical group comprised 66 patients (57%), and all of these died; the cause of death was unsuspected, suspected, or diagnosed after hospital admission from the emergency department. Of the surgical group, 36 patients (72%) survived, whereas 14 patients (28%) died. The surgical management comprised partial cardiopulmonary bypass in 31 patients that included seven deaths, simple aortic cross-clamping in 14 that included six deaths, and nonheparinized bypass in four that included one death. The incidence of paraplegia was 3.2% (one patient) with cardiopulmonary bypass, 28.5% (four patients) with simple aortic cross-clamping and none with nonheparinized bypass.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Age as a determinant for selection of porcine bioprostheses for cardiac valve replacement: experience with Carpentier-Edwards standard bioprosthesis.

Almost exclusive use of Carpentier-Edwards porcine bioprostheses for cardiac valve replacement in 1194 patients between 1975 and 1987 at the authors' institutions has afforded the opportunity for a more scientific basis for prosthesis selection for subsets of patients, with regard to age and valve-related complications. The present study, performed according to previously established guidelines, investigated the influence of patient age and valve position as determinants of durability of 1315 porcine implants in terms of the following valve-related complications: structural valve deterioration, nonstructural dysfunction, thromboembolism, antithromboembolic therapy-related hemorrhage and prosthetic valve endocarditis. Age groups were as follows: 35 years and younger, 36 to 50 years, 51 to 65 years, and 66 years or older. Thromboembolism was found to be less common in the younger age groups, and significantly less common in patients following aortic compared to mitral valve replacement. The age group assessment for antithromboembolic therapy-related hemorrhage, nonstructural dysfunction and prosthetic valve endocarditis revealed no difference between positions or age groups. Patient age was found to be the major predictor of, and inversely related to, structural valve deterioration. In addition, porcine bioprostheses in the aortic position were shown to have durability superior to that of similar valves in the mitral position. Structural valve deterioration has very little influence on valve-related mortality and residual morbidity. This study thus supports the implantation of porcine bioprostheses in somewhat younger patients than would be advisable for mitral prostheses. The authors now recommend the selective implantation of porcine bioprostheses in the aortic position in patients over 65 years of age, and in the mitral position in patients over 70 years of age.

Adolescent↗