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Biomedical subjects

G F Tyers

Publications and source records attributed to G F Tyers.

At least 91 records · Page 5Linked to original sources
PubMed1981

Use of cold cardioplegic solution for vein graft distention and preservation: a light and scanning electron microscopic study.

To evaluate the effect of a cardioplegic solution on the endothelium of the saphenous vein, portions of this vein were harvested from each of 5 patients undergoing coronary artery bypass operation. Each sample was divided into five segments. One segment was distended with heparinized saline solution, one with heparinized blood, and one with heparinized cardioplegic solution (25 mEq of potassium per liter). All of the distending solutions were kept at 10 degrees C, and pressure was carefully limited to 200 mm Hg. The fourth segment of vein was distended with heparinized saline solution but no effort was made to limit distending pressure, and the fifth segment was not distended. All samples were then examined with light and scanning electron microscopy. There were no great morphological differences in the endothelium of veins distended to 200 mm Hg with saline solution, blood, or cardioplegic solution. The morphology of these samples compared favorably with the control vein endothelium although scattered areas of endothelial disruption were present in every sample. Veins distended without pressure control showed massive endothelial disruption. The particular solution used to distend the sephenous veins is not as important as limiting the distending pressure.

Blood↗
PubMed1981

Multiprogrammable pacemakers.

Since 1962 it has been possible to change, by noninvasive means, the functions of implanted pacemakers. This study reports a 3-year multicentre experience, in 164 patients, with a multiprogrammable pacemaker that offers a wide range of choices within five variables: mode, rate, pulse width, sensitivity and telemetry (over 3000 combinations). In a selected series 83% of implanted pacemakers were programmed for medical indications and 100% for multiparameter follow-up studies. The advantage and disadvantages of three are compared. There is little doubt that multiprogrammable pacemakers can reduce the frequency of reoperation in any large series.

Arrhythmias, Cardiac↗
PubMed1980

Recent experience with tuberculous pericarditis.

Twelve patients with tuberculous pericarditis were found among 1,194 patients with tuberculosis treated at the University of Texas Medical Branch over a 10-year period, an incidence of 1%. Surgical treatment was undertaken in 4 patients, and the rest were treated medically. The surgically treated patients had no major complications, and none of them died. In the medically treated group, however, 1 patient died, 1 had an anaerobic empyema, and 1 experienced respiratory arrest. In addition, the average hospital stay was 33 days less in the surgically treated group. Early surgical intervention should be carried out in patients with tuberculous pericarditis who do not respond promptly to adequate antituberculosis chemotherapy.

Adult↗
PubMed1980

Mediastinoscopic removal of a superior mediastinal foreign body.

A metallic mediastinal foreign body, which eroded into the esophagus and resulted in a mediastinal abscess, was removed through the mediastinoscope. Tubes for drainage and irrigation were easily inserted after the pus had been entirely drained. Satisfactory low-risk treatment was accomplished without the need for major surgical intervention.

Abscess↗
PubMed1980

The effects of electrode position on the detection of the transvenous cardiac electrogram.

Adequate sensing of the cardiac electrogram is a necessary requisite for all demand cardiac pacemakers. In order to define better the effects of position of the sensing electrode on the ability of the pacer to detect the electrogram, a specially designed lead system with a movable, large surface area (50 mm2) proximal ring electrode and a small surface area distal tip electrode was placed transvenously in 12 mongrel dogs. As the sensing electrode was moved away from the right ventricular apex, there were slight but insignificant decreases in R wave amplitude. When the electrode was moved retrograde through the tricuspid valve into the atria there was a marked decrease in R wave sensing; however, this was accompanied by a significant increase in P wave amplitude. Therefore, with a large surface area electrode, direct contact with the myocardium is not needed for the detection of adequate P and R waves. In addition, a pacer lead system utilizing this sliding sensing electrode design could be used to optimize sensing position, either for atrial or ventricular sensing pacemakers.

Animals↗
PubMed1979

Myocardial stimulation impedance: the effects of electrode, physiological, and stimulus variables.

With exposed metal at the electrode tissue interface (8 mm2, 28 mm2, 57 mm2), myocardial threshold stimulation impedance increased as pulse duration was lengthened, with left ventricular intramyocardial stimulation, and with the smaller surface area electrode. An 0.5 mm2 differential-current-density electrode, which eliminated direct metal-to-tissue contact at the electrode-myocardial interface, was associated with notably higher impedances than each of the three metal tip electrodes and did not show increasing impedance levels with changes in pulse duration, confirming the minimization of polarization energy losses with this device. The majority of electrode, electrode tissue interface, and myocardial variables that are characterized by high threshold stimulation impedance are associated with low threshold energy requirements for pacing and reduced pacemaker power source drain. No accurate information about sensing impedances can be derived from current knowledge of pacing impedance.

Acid-Base Imbalance↗
PubMed1979

Intrapleural instillation of quinacrine for treatment of recurrent spontaneous pneumothorax.

We used intrapleural instillation of quinacrine hydrochloride in 20 patients (Group A) with recurrent spontaneous pneumothorax (one bilateral) and compared their clinical course with 19 patients who underwent thoracotomy and scarification or pleurectomy (Group B) and 63 patients treated by tube thoracostomy alone (Group C). In Group A, there was one complication of treatment, a pneumothorax immediately following tube removal, which necessitated repeat tube thoracostomy, and there was one late ipsilateral recurrence 2 years after treatment. These 20 patients with 21 recurrent spontaneous pneumothoraces treated with intrapleurally administered quinacrine have been followed for from 6 months to more than 4 years with only one late recurrence on the treated side. Eight patients in Group B had postoperative complications: 2 patients who had had pleurectomy required reoperation for postoperative bleeding; lobar pneumonia developed in 3; 1 had lack of total expansion of the lung; an intrathoracic hematoma developed in 1; and an ipsilateral pneumothorax necessitating tube thoracostomy developed in 1. In Group C, the rate of recurrence of pneumothorax was 23% during the first year following treatment. Intrapleural instillation of quinacrine is a simple, low-risk, reliable, and effective treatment for recurrent spontaneous pneumothorax, and is equally as effective as thoracotomy and scarification.

Adolescent↗