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Biomedical subjects

G F Tyers

Publications and source records attributed to G F Tyers.

At least 19 recordsLinked to original sources
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↗
PubMed1990

Balloon embolization of latrogenic aortocoronary arteriovenous fistula.

A detachable latex balloon was used to occlude an iatrogenic aortocoronary arterio-venous fistula. The aim of providing retrograde myocardial perfusion was not achieved to any significant degree because of rapid recruitment of collateral venous routes to the coronary sinus. This may have implications for the effectiveness of deliberate grafting of the coronary venous system with proximal venous ligation, as has been recommended when the coronary arterial system is small and diffusely diseased.

Angioplasty, Balloon, Coronary↗
PubMed1990

Current status of sensor-modulated rate-adaptive cardiac pacing.

In one third of patients requiring permanent cardiac pacing, sinoatrial response to exercise is inadequate. This has led to the development of a number of nonatrial sensors capable of increasing stimulation rate in response to metabolic demand. Initial sensor-modulated pacemakers were designed for use in the ventricle. This review was undertaken to compare ventricular rate-adaptive pacing with dual chamber and nonrate-adaptive atrial modes. Rate-adaptive ventricular pacing is primarily indicated in patients with complete heart block and nonfunctional atria in whom increased rates are not associated with the development of myocardial ischemia or retrograde conduction. A responsive atrium remains the best measure of metabolic demand, and devices capable of maintaining atrioventricular (AV) sequencing provide superior hemodynamic performance at usual activity levels. In addition, preserved AV relations reduce the incidence of new atrial fibrillation and stroke. Newer devices combining the advantages of atrial and nonatrial rate modulation with the preservation of AV synchrony will best utilize the developing sensor technologies.

Animals↗
PubMed1990

The Carpentier-Edwards standard porcine bioprosthesis. A first-generation tissue valve with excellent long-term clinical performance.

The Carpentier-Edwards standard porcine bioprosthesis was implanted in 1190 patients (1201 operations, 1303 valves) between January 1975 and June 1986; most implants were before 1982. The mean age of the patients was 57.2 years (range 8 to 85 years). The early mortality was 7.6% (aortic valve replacement 5.1%, mitral valve replacement 8.8%, and multiple valve replacement 15.3%). Late mortality was 3.9% per patient-year (aortic valve replacement 3.6%, mitral valve replacement 4.2%, and multiple valve replacement 3.8%). The total cumulative follow-up period was 6737 years. Thromboembolism was 1.5% per patient-year (fatal 0.4% per patient-year) (minor 0.6%, major 0.9%); antithromboembolic therapy-related hemorrhage was 0.5% (fatal 0.1%); prosthetic valve endocarditis was 0.6% (fatal 0.2%); nonstructural dysfunction was 0.5% (fatal 0.2%); and structural valve deterioration and/or primary tissue failure was 1.5% per patient-year (fatal, 0.2% per patient-year). Thromboembolism and structural valve deterioration were the significant complications, structural valve deterioration occurring primarily between the sixth and 10th year of evaluation. The overall patient survival was 65.0% for aortic valve replacement and 54.8% for mitral valve replacement (p less than 0.05) at 10 years. The patients were classified as 92.9% New York Heart Association functional classes III and IV preoperatively and 92.3% classes I and II postoperatively. Freedom at 10 years from thromboembolism was 84.3% for aortic valve replacement and 76.5% for mitral valve replacement (p = 0.05); structural valve deterioration was 78.6% for aortic valve replacement and 71.6% for mitral valve replacement (p less than 0.05); reoperation was 74.4% for aortic valve replacement and 67.1% for mitral valve replacement (p less than 0.05). Freedom from all valve-related complications at 10 years was 58.9% for aortic valve replacement and 46.8% for mitral valve replacement (p less than 0.05); valve-related mortality was 89.5% for aortic valve replacement and 82.6% for mitral valve replacement (p = not significant); mortality and reoperation was 58.9% for aortic valve replacement and 46.8% for mitral valve replacement (p less than 0.05); mortality and residual morbidity (treatment failure) was 87.2% for aortic valve replacement and 75.1% for mitral valve replacement (p = not significant); mortality, residual morbidity, and reoperation were 66.3% for aortic valve replacement and 54.9% for mitral valve replacement (p less than 0.05). The standard Carpentier-Edwards porcine bioprosthesis has provided satisfactory clinical performance and has afforded patients excellent quality of life.

Adolescent↗
PubMed1989

FDA recalls: how do pacemaker manufacturers compare?

To evaluate an apparent perception that there is no difference in reliability among the products of the major cardiac pacing system manufacturers, an extensive review of US Food and Drug Administration regulatory actions was performed. The study period was July 1974 through June 1987. The total number of affected devices was collected for each manufacturer. Available sales data were used to calculate their percentage of recalled products during two time periods. The percentage of potentially high-risk devices (Food and Drug Administration class I and II recalls) was high for one company, moderate for one, and relatively low for the rest. Potential biases in some other sources of reliability information, as well as implications for regulatory policies, are discussed. The data reported establish that there have been past deficiencies in recall management. Although further pacing device recalls are probable, appropriate early regulatory and manufacturer action should help to assure that both the immense cost and patient distress caused by pacer and related product problems in the past can be minimized in the future.

Equipment Failure↗
PubMed1989

Atrial pacing: efficacy and safety.

Atrial pacing has the advantages of simplicity, maintenance of AV synchrony, and economy. The major detraction has been the potential for deterioration of atrioventricular conduction. In this study, we followed 43 patients with sick sinus syndrome treated with atrial (AAI) pacing. Excellent initial implant parameters were obtained in all. Three early lead repositionings were required. Minor sensing and pacing problems could all otherwise be handled by reprogramming. Follow-up for a mean of 25 +/- 20 months demonstrated excellent performance of the pacing systems. Pacing and sensing thresholds and lead impedance indicated excellent lead performance. There were no late lead failures. Nine patients have had mild deterioration in atrioventricular conduction and one of these had a change to DDD pacing at the time of elective battery change. All patients are asymptomatic. Thus, chronic atrial pacing in selected patients is safe and reliable with good chronic lead performance and low risk of subsequent conduction system disease.

Adolescent↗
PubMed1988

The Carpentier-Edwards standard porcine bioprosthesis: long-term evaluation of the high pressure glutaraldehyde fixed prosthesis.

The Carpentier-Edwards standard porcine bioprosthesis was implanted in 1,000 operations (988 patients with 1,092 valves) between 1975 and 1981. The mean age of the patients was 56.8 years (range 8 to 85 years). During the years 1975 and 1981, approximately 97% of the total valvular surgery population received the prosthesis. The early mortality was 7.8% (including patients with concomitant procedures including coronary artery bypass and ascending aortic aneurysm resection). Late mortality was 3.8% per patient-year. The total cumulative follow-up was 5,937 years. Thromboembolism (TE) was 1.3% per patient-year (fatal 0.4%/patient-year) (minor 0.4%; major 0.9%); antithromboembolic therapy-related hemorrhage (ATH) 0.5% (fatal 0.1%); prosthetic valve endocarditis (PVE) 0.5% (fatal 0.2%); periprosthetic leak (PPL) 0.4% (fatal 0.2%); clinical valve dysfunction (CVD) 0.2% (fatal 0.02%); and structural valve deterioration (SVD)/primary tissue failure 1.6% per patient-year (fatal 0.2%/pt-yr). Thromboembolism and SVD occurring primarily between the sixth and tenth year of evaluation, were the significant complications. The overall patient survival was 60.5% +/- 2.4% at 10 years. The patients were classified as 93.5% NYHA functional Class III and IV, preoperatively and 93.1% Class I and II, postoperatively. The freedom at 10 years from TE was 82.9% +/- 2.7%; SVD 76.9% +/- 2.9%; and reoperation 70.8% +/- 3.1%. Freedom from all valve-related complications at 10 years was 54.3% +/- 3.1%; valve-related mortality 86.4% +/- 2.3%; mortality and reoperation (valve failure) 64.0% +/- 3.2%; mortality and residual morbidity (treatment failure) 82.3% +/- 2.6%; and mortality, residual morbidity, and reoperation (valve failure and dysfunction) 60.6% +/- 3.2%. There were 61 valve-related deaths of a total 352 deaths (early 7, late 54) (TE 21; ATH 7; CVD 1; PVE 12; PPL 9; and SVD 11). Valve-related reoperations were performed in 128 patients (TE 3; CVD 4; PVE 14; PPL 17; and SVD 90). The standard Carpentier-Edwards porcine bioprosthesis has provided very satisfactory clinical performance and afforded patients excellent quality of life. Primary tissue failure is the significant long-term complication.

Adolescent↗