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Biomedical subjects

G F Tyers

Publications and source records attributed to G F Tyers.

At least 73 records · Page 4Linked to original sources
PubMed1987

A tri-institutional comparison of tissue and mechanical values using a patient-oriented definition of "treatment failure".

Selection of valve type for predominant usage is obscured by limiting the analysis to prosthesis-related rather than patient-oriented failure modes. In this report, "treatment failure" is defined as a valve-related death or permanent patient disability; successful reoperations are excluded, and emboli with permanent residua are included. Results with the Starr-Edwards Silastic ball valve (Oregon) and the Hancock (Stanford) and Carpentier-Edwards (Vancouver) porcine valves are compared using this new definition of treatment failure. Evaluated according to structural failure, the mechanical valve is superior to the tissue valve, and using the Stanford definition of valve failure, it becomes so between 5 and 10 years. Using treatment failure, tissue valves are superior at 5 years; at 10 years in the aortic position, the results are comparable; and in the mitral position at 8 to 10 years, tissue valves show a continued but small advantage.

Aortic Valve↗
PubMed1986

Transvenous atrial pacing in the management of sick sinus syndrome following surgical treatment of the univentricular heart: case report and review.

An 11-year-old boy with univentricular heart type A-III underwent surgical treatment at age 10 with a modified Fontan operation. Six months postoperatively he developed intermittent periods of cyanosis and fatigue associated with profound sinus bradycardia and nodal escape. After demonstrating normal atrioventricular conduction, a transvenous atrial pacemaker was implanted. This produced a marked clinical improvement. Transvenous atrial pacing is a satisfactory method of treating sinus node dysfunction in patients with univentricular heart following the Fontan operation provided that there is normal AV conduction.

Child↗
PubMed1986

Carpentier-Edwards supra-annular porcine bioprosthesis. Clinical experience and implantation characteristics.

The investigational Carpentier-Edwards supra-annular valve was implanted in 592 patients from November, 1981, to February, 1984 (aortic valve replacement in 286, mitral valve replacement in 259, and multiple valve replacement in 47, for a total of 638 prostheses). A previous cardiac operation had been performed in 77 patients (13%). Concomitant procedures were performed in 202 patients (34.1%), including coronary artery bypass in 163 patients. The patient evaluation was 98.6% complete. The early mortality was 7.4% (44 patients) and the late mortality was 6.2% per patient-year (41 patients). The valve-related causes of late mortality were thromboembolism (five), anticoagulant-related hemorrhage (one), and prosthetic valve endocarditis (one). The overall patient survival, including operative death, was 85% at 2 years. The linearized occurrence rate for valve-related complications was 5.6% per patient-year (37 events)--thromboembolism 2.7% per patient-year (18) anticoagulant-related hemorrhage 1.2% (eight), prosthetic valve endocarditis 0.8% (five), and periprosthetic leak 0.9% per patient-year (six). There were no cases of primary tissue failure or structural failure. At 2 years, the freedom from valve-related complications was 86.9%, from valve-related mortality, 98.7%, and from valve-related mortality and reoperation, 97.7%. This valve is fixed in glutaraldehyde at low pressure and is designed to improve durability. It has provided a low incidence of valve-related complications without structural failure. The structural design of the prosthesis does not always conform to the anatomy of bicuspid aortic valves.

Bioprosthesis↗
PubMed1985

Transvenous atrial pacing following amputation of the atrial appendage at open heart surgery.

The right atrial appendage is frequently amputated at the time of open heart surgery. In this study we report implantation and chronic follow-up pacing data on 17 patients in whom either actively fixated screw-in leads or passively fixated tined "J" leads were implanted into the trabeculae at the base of the atrial appendage. Chronic follow-up demonstrated excellent chronic pacing thresholds and atrial sensitivity thresholds in those patients in whom these measurements could be made. It is therefore concluded that satisfactory atrial pacing can be achieved in patients who have previously undergone amputation of the atrial appendage during open heart surgery.

Adolescent↗
PubMed1983

Trocar cannulation of the ascending aorta: a new technique.

An improved technique for cannulating the ascending aorta has been developed and used in 229 consecutive open-heart procedures without complication. Advantages of the method include speed and ease of cannula insertion, elimination of the need for partial-occlusion clamping of the aorta, minimization of the risk of introducing air, minimization of blood loss, and facilitation of distal cannulation in patients with short aortas.

Aorta↗
PubMed1983

Two mechanisms of arrhythmia induction by a DDD pacemaker: a case report.

A 68-year-old man with sick sinus syndrome and a history of intermittent atrial fibrillation was treated by implantation of a DDD pacemaker. He subsequently developed recurrent episodes of shortness of breath and tachycardia. Investigation revealed two different arrhythmias, both induced by the pacemaker: (1) a tachycardia in which the dual-chamber pacemaker system provided the antegrade limb and the AV node provided the retrograde limb and (2) a triggered, ventricularly paced tachycardia caused by the pacemaker sensing atrial fibrillation waves. Both rhythms were abolished by reprogramming to the DVI mode.

Aged↗
PubMed1982

Experience with the Carpentier-Edwards porcine valve prosthesis in 700 patients.

The Carpentier-Edwards porcine valve prosthesis has afforded our patients a satisfactory quality of life and a low incidence of valve-related complications at follow-up periods of up to five years. From December, 1975 to March, 1980, 768 prosthesis were implanted in 700 patients (aortic valve replacement [AVR], 334; mitral valve replacement [MVR], 292; tricuspid valve replacement [TVR), 6; and multiple valve replacement, 68). One hundred and thirty-seven patients (19.6%) had had previous cardiac operations. Concomitant aortocoronary bypass was performed in 127 patients (18.1%). There were 52 hospital deaths, for a mortality of 7.4% (AVR, 4.8%; MVR, 9.2%; multiple valve replacement, 11.8%). Total follow-up was 1,047 patient-years (range, 6 to 60 months, mean, 19.4 months). There were 33 late deaths (AVR, 1.7% per patient-year; MVR, 4.0% per patient-year; multiple valve replacement, 8.1% per patient-year). Eight percent of AVR patients and 47% of MVR and multiple valve replacement patients were taking anticoagulants. The valve-related complications (expressed as events per 100 patient-years) were as follows: (1) thromboembolism (AVR, 0.94; MVR,. 1.42; multiple valve replacement, 4.62); (2) infective endocarditis (AVR, 0.94; MVR, 0.24; multiple valve replacement, 2.31); (3) periprosthetic leak (AVR, 0.94; MVR, 0.71; multiple valve replacement, 3.46); and (4) valve dysfunction (MVR, 0.24). The only case of valve dysfunction was a calcified mitral prosthesis in a 13-year-old girl. Actuarial survival, including operative deaths, was as follows: AVR, 90.5% at 36 months; MVR, 84% at 36 months; and multiple valve replacement, 74% at 24 months. Of surviving patient, 93.6% were in New York Heart Association Class I or II at follow-up evaluation.

Adolescent↗
PubMed1982

Continuous monitoring of mixed venous oxygen saturation in cardiac surgery.

Serial measurement of mixed venous oxygen saturation is useful in the care of critically ill patients. It is an index of cardiac output and overall tissue perfusion. Previously, lack of refinement of the technology for continuous monitoring of mixed venous oxygen saturation deterred its clinical application. The authors evaluated the Oximetrix ShawTM catheter oximeter system between May 1980 and April 1981 in 84 high-risk and moderately high-risk patients. Fifty-four had undergone only myocardial revascularization while 30 had undergone valvular or combined procedures. In 20 patients with compromised left ventricular function (mean ejection fraction of less than 40%) continuous mixed venous oxygen saturation was compared to hemodynamic parameters in an intraoperative and early postoperative study. The results indicated that satisfactory mixed venous oxygen saturation (more than 65%) correlated with normal hemodynamic measurements including cardiac output and cardiac index. In general, a fall in mixed venous oxygen saturation of more than 10% was noted before the mean blood pressure, heart rate or pulmonary capillary wedge pressure changed. Cardiac output, cardiac index, systemic vascular resistance and left ventricular stroke work index were found to change in association with a change in mixed venous oxygen saturation. A fall (mixed venous oxygen saturation less than 65%) can be related to: (a) abnormal hemodynamic status--reduced cardiac output, hypotension, elevated systemic vascular resistance and arrhythmias, (b) abnormal oxygen demand--shivering, suctioning, positioning and pyrexia and (c) abnormal oxygen supply--anemia, airway obstruction and altered diffusion of oxygen at the alveolar capillary membrane. The Oximetrix system proved reliable. Mixed venous oxygen saturation is a nonspecific indicator of hemodynamic status. Continuous monitoring of the mixed venous oxygen saturation facilitates optimal patient management by immediately alerting intensive care personnel to the development of inadequate tissue perfusion.

Adult↗
PubMed1982

Primary cardiac tumors: experience with 25 cases.

The case histories of patients with primary cardiac neoplasms are presented. The mean age was 49.6 years and females predominated (17:8). Nineteen of the tumors were benign (76%), 18 myxomas and one mesenchymal hamartoma. There were six malignant neoplasms; two myxosarcomas, two rhabdomyosarcomas, one skeletal angiomatosis, and one malignant melanoma. The clinical presentation was congestive heart failure in 17 patients and peripheral embolization in five (one patient with both). There were four asymptomatic patients. Antemortem diagnosis was made in 20 patients and five were discovered at autopsy. After 1970, almost 95% of the patients were diagnosed preoperatively while only 14% of the patients had preoperative diagnosis before 1970. Cardiac catheterization and echocardiography were the most useful diagnostic procedures performed but a computed tomographic scan of the heart performed in a patient with right ventricular hamartoma was of great value in delineating the lesion. Twenty-one patients underwent a total of 26 operations but complete excision of the lesion was possible in only 16 patients. Three patients underwent extensive resection and reconstruction. Associated procedures consisted of coronary artery bypass grafts in two patients, mitral valve annuloplasty in one, and a right lung biopsy. Although there was no operative mortality following the original procedure, one patient died after a third operation for recurrence and another underwent unsuccessful emergency pericardiectomy. All patients with malignant lesions died from recurrence 6 to 13 months postoperatively while only three patients in the benign group died and these of unrelated causes. Surgical resection is the treatment of choice for all primary cardiac neoplasms since it is curative in the benign tumors and may prolong life for up to a year with malignant tumors.

Adolescent↗