Search PubMed⌕ Search

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↗
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↗
PubMed1979

Subclavian steal syndrome: an update.

The clinical findings in this series of 22 cases of subclavian steal syndrome showed a predominance of men (13:9), a mean age of 51 years, and a predominance of left subclavian artery obstruction. There was a blood pressure differential of more than 20 mm Hg and diminished pulses ipsilaterally in most. Main indications for surgical repair were transient neurologic symptoms. Twenty-one of our patients had surgical repair of the subclavian steal syndrome; six had concomitant carotid artery surgery. The most common surgical procedure performed consisted of a carotid subclavian bypass graft. One patient had only carotid revascularization; 19 patients have had good long-term results. One patient, with tetralogy, died and three had complications. The asymptomatic or mildly symptomatic patient may be given a trial of medical treatment. Symptomatic patients can have extrathoracic bypass with a very low risk. Surgery is indicated if significant associated carotid lesions are present.

Adult↗
PubMed1979

Runaway pump head: new cause of gas embolism during cardiopulmonary bypass.

Massive gas embolism was narrowly avoided during a recent case of cardiopulmonary bypass for aortic valve replacement. Cause of the mishap was an arterial pump head that had rapidly accelerated spontaneously, emptying the oxygenator of blood within seconds. No gas entered the patient's vascular system, but a period of circulatory arrest was required in order to purge the extracorporeal circuit of gas and to re-establish blood flow. Only an instantaneous response by the perfusionist prevented massive gas embolism.

Cardiopulmonary Bypass↗
PubMed1978

Similarity of clinical and laboratory results obtained with microporous teflon membrane oxygenator and bubble-film hybrid oxygenator.

For 80 elective clinical cardiopulmonary bypasses we alternately used either a commercial microporous Teflon membrane oxygenator or a commercial hybrid bubble-film oxygenator. Setup time was a little longer with the membrane unit (20 minutes), but priming volume (2,250 ml) was the same. No problems were encountered with the hybrid oxygenator. However, despite our monitoring of additional variables, including shim and inlet pressure and recirculation flow, gas exchange abnormalities were encountered in 5 patients on whom the membrane oxygenator was used; in 4 of these cases the abnormalities were encountered prior to our recognition of the potential for occasional internal shunting with this device. There were no hospital deaths. When the two groups, matched except for oxygenator selection, were compared, there were no significant differences clinically or hematologically. For cardiopulmonary bypass of 2 hours or less, both oxygenators studied are definite improvements over previous silicone membrane and high-gas-flow bubble oxygenators. However, lower cost and reduced complexity favor the hybrid oxygenator.

Blood Glucose↗
PubMed1978

Current status of pacemaker power sources.

After years during which pacers of very similar design and capabilities were provided by a small number of manufactures, many different lithium, halogen, rechargeable, and nuclear power sources are now available. The variety of chemistries, methods of construction, and sealing techniques used in the batteries of the different manufacturers is almost unlimited. This has made it necessary for physicians who implant and follow pacer to acquire a general knowledge of the field if they are to make an informed choice of pacemaker power source for implantation and if they are to manage recalls with a minimum of patient and physician trauma. More experience is required before it can be definitely determined which of the new pacer power sources will prove superior, but when coupled with well-designed, hermetically sealed pulse generators, all are capable of providing continuous pacing for at least 5 years and the 10-year pacemaker is now a probability.

Animals↗
PubMed1978

Symptomatic deep venous thrombosis of the arm associated with permanent transvenous pacing electrodes.

From October 1970 to May 1977, a total of 212 pacemakers were implanted at the Milton S. Hershey Medical Center of Pennsylvania State University, Hershey. During this period, we encountered five patients with symptomatic thrombosis of the subclavian vein, a rate for this complication of approximately 2 percent. Although this complication was reported only rarely prior to 1976, we believe that symptomatic subclavian thrombosis after insertion of a transvenous pacemaker electrode occurs more frequently than previously suspected. The etiology, pathogenesis, and treatment of this interesting condition are discussed.

Aged↗