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Biomedical subjects

W O'Neill

Publications and source records attributed to W O'Neill.

At least 55 records · Page 3Linked to original sources
PubMed1985

Use of the pill electrode for transesophageal atrial pacing.

The pill electrode, which was developed for esophageal electrocardiography, has found application in transesophageal atrial pacing during procedures such as conversion of tachycardia, electrophysiologic measurement, and acceleration of heart rate to produce stress during cardiac imaging studies. This paper presents theoretical studies that examine the relationship of interelectrode distance, current level, and pulse duration to the achievement of successful capture. Theoretical results agree with our clinical findings, i.e., current levels of 25 mA are effective to sustain capture; increased pulse duration reduces current requirements; and close bipolar spacing combines efficacy with safety. Results of animal studies performed to assess the extent of esophageal burn injury reveal that current levels in excess of 75 mA are required to produce lesions in short-term (under 30 minutes) pacing, and greater than 60 mA in long-term (4 hours) pacing. These results are based on experiments using a pulse duration of 2 ms, and the current levels that produce injury will be considerably lower if longer pulse durations are used. Typical current levels and pulse durations for successful capture are presented for 46 subjects in several new clinical applications. Termination of tachycardia, basic electrophysiologic measurements, and controlled acceleration of heart rate can be performed noninvasively with this technique.

Adolescent↗
PubMed1984

Effects of reperfusion on complete heart block complicating anterior myocardial infarction.

Two patients with complete heart block complicating extensive anterior myocardial infarction underwent late (greater than 40 hours) coronary reperfusion with angioplasty. One to one atrioventricular conduction was restored within minutes of reperfusion despite a lack of measurable ventricular muscle salvage as demonstrated by ventriculography 1 week later. The evidence favors reversible ischemia rather than extensive necrosis of the proximal conduction system as the mechanism of heart block in this subgroup of patients.

Adult↗
PubMed1984

Identification of patients with improved survival following coronary bypass surgery.

This study was designed to determine whether left ventricular performance measured noninvasively from the systolic time intervals could identify patients in whom coronary bypass surgery may improve survival. 71 patients with two- or three-vessel disease undergoing coronary bypass surgery were compared with 78 matched medically treated patients. All patients had recuperated from myocardial infarction by a mean of 17.6 months when systolic time intervals were performed. Surgical and medical patients were classified preoperatively into those with normal and those with abnormal left ventricular performance by preejection period/left ventricular ejection time (PEP/LVET less than or equal to 0.42 and greater than 0.42, respectively). Survival was analyzed by life table and log-rank test. Cumulative 5-year survival in patients with normal left ventricular performance was not statistically different in surgical and medical groups (96 vs. 93%, respectively). In contrast, cumulative survival in patients with abnormal left ventricular performance was significantly greater in the surgical group when compared to the medical group (84 vs. 62, p less than 0.01). Among the patients with abnormal left ventricular function, the mean PEP/LVET and the average vessel disease were not different in the medical and surgical groups. Multivariate analysis of 17 other clinical and laboratory risk variables were not different between these two groups. It is concluded that coronary bypass surgery my improve survival in patients with two- or three-vessel disease and left ventricular dysfunction.

Actuarial Analysis↗
PubMed1983

Natural history of coronary heart disease: a study of 586 men surviving an initial acute attack.

A total of 586 men who survived an initial attack of unstable angina or myocardial infarction have been followed for up to 15 years. A policy of early mobilization and sustained risk factor advice was employed. A conservative approach to treatment was adopted during the acute and follow-up stages. Drugs were employed only for symptomatic reasons, and only two patients proceeded to coronary artery bypass surgery. Survival at 5, 10, and 15 years was 80%, 61%, and 43%. Older patients and those with more severe initial attacks had a higher mortality, but these factors did not relate to combined fatal and nonfatal recurrence of myocardial infarction. Of 22 studies reviewed, 18 report a higher mortality than does our study. Four studies, none strictly comparable, report a similar 5-year mortality. A conservative approach to management does not appear to be harmful and may be beneficial.

Age Factors↗
PubMed1983

Disseminated tuberculosis in a renal transplant recipient: presentation as an anterior mediastinal mass.

A 26-year-old man who had had a successful cadaveric renal transplant six months previously was admitted for evaluation of fever and dysuria. Chest x-ray revealed a new left pleural effusion, bilateral nodular parenchymal densities, and an anterior mediastinal mass. A biopsy of the mediastinal mass to exclude concurrent malignancy and positive AFB stains from pleural fluid and urine confirmed a diagnosis of disseminated tuberculosis.

Adult↗
PubMed1982

Radionuclide evaluation of postextrasystolic potentiation of left ventricular function induced by atrial and ventricular stimulation.

Postextrasystolic potentiation of left ventricular function induced by ventricular and atrial stimulation was compared in 10 patients using radionuclide ventriculography. After insertion of pacing wires, a preliminary radionuclide ventriculogram was obtained and then ventricular and atrial trigeminy was induced in random order, each with identical R-R coupling intervals, each for 6 to 10 minutes. During the stimulation studies, radionuclide data were acquired in electrocardiographic gated list mode format. Left ventricular ejection fraction and relative end-diastolic and end-systolic volume changes were measured for each reformatted composite sinus, atrial and ventricular premature beat and potentiated beat. The volume changes were normalized to the count-based values obtained for the sinus beat of the appropriate study. Postextrasystolic potentiation induced by either ventricular or atrial stimulation was characterized by similar significant increases in left ventricular ejection fraction (mean +/- standard deviation 7 +/- 3 percent, p less than 0.01 versus 7 +/- 5 percent, p less than 0.01; difference not significant [NS]) and decreases in relative end-systolic volume (-12 +/- 12 percent, p less than 0.01 versus -12 +/- 8 percent, p less than 0.01; NS) but little change in relative end-diastolic volume (+5 +/- 10 percent, NS versus +4 +/- 7 percent, NS; NS). This was despite a longer compensatory pause (1,120 +/- 220 versus 1,050 +/- 190 ms, p less than 0.01) after the ventricular premature beat. It is concluded that there is no difference in the postextrasystolic potentiation induced by atrial or ventricular premature stimulation.

Adult↗
PubMed1982

The QT greater than QS2 syndrome: a new mortality risk indicator in coronary artery disease.

In the normal population the duration of electrical systole (QT) is shorter (mean -26 +/- 13 ms, 1 standard deviation) than that of electromechanical systole (QS2), which it closely parallels throughout the range of resting heart rate. This close association prompted the hypothesis that the duration of QT may be more closely linked physiologically to QS2 than to the heart rate and hence may provide a more potent prognostic indicator than the relation of QT to heart rate. The present study was designed to test this hypothesis. On hundred stable patients 14 months after myocardial infarction were followed up an average of 43 months. Twenty patients had prolongation of QT relative to QS2 (QT greater than QS2) and 13 patients had long QT corrected for heart rate (QTc). There were 20 deaths (16 sudden). The cumulative 5 year survival rate was 35% in patients with QT greater than QS2 and 91% in patients with QT greater than or equal to QS2 (p less than 0.001). There was no significant difference in survival in patients with long QTc compared with patients with normal QTc (69 versus 82%). Univariate and multivariate analysis for the association of QT greater than QS2 with known risk factors, clinical descriptors, drug therapy, systolic time intervals (preejection period/left ventricular ejection time), and frequency of 1, 2 and 3 vessel coronary occlusive artery disease revealed that only the presence of abnormal preejection period/left ventricular ejection time added significantly to the presence of QT greater than QS2 in stratifying 5-year survival into high and low risk groups. Thus, in patients with coronary artery disease, the presence of QT greater than QS2 provides a new risk indicator that is more potent than QT corrected for heart rate.

Aged↗
PubMed1980

Calcitonin in tissues of thyroidectomized monkey.

Immunochemical studies indicate that immunoreactive calcitonin (iCT) is present in many tissues of monkey following thyroidectomy (thx) (e.g. liver, thymus, lung). Extrathyroidal iCT may play a role in calcium metabolism.

Animals↗
PubMed1977

The role of iodine in the pathogenesis of thyroid enlargement in rats with chronic renal failure.

In rats with mild renal failure produced by a 2/3 nephrectomy on one side followed by a total nephrectomy on the other, ingestion of a high (10 mg/kg) iodine diet for two months resulted in thyromegaly, high serum iodine levels and a good correlation between thyroid weight and serum iodine (r = 0.75, P less than 0.01) or thyroid weight and blood urea nitrogen (r = 0.745, P less than 0.01). Iodine may potentiate the effects of unidentified gointrogens that accumulate in rats with renal failure. Since the serum iodine levels were higher in the animals with renal failure, it is also possible that iodine alone may have been responsible for the observed differences in thyroid weight.

Animals↗
PubMed1977

Visual masking by translation equivalents in bilinguals.

Masking thresholds for common words as a function of the relationship between target and mask were assessed using French-English bilingual subjects. Five target-mask combinations were employed. Two control conditions involved unrelated pairs presented in either the same or both languages. The experimental conditions employed masks that were subordinate to the target, e.g., animal-horse, masks that were thr translation equivalents of the targets, and masks which were homophones of the target. Homophones were superior masks compared to same-language, unrelated masks which were in turn superior to subordinately related masks. Translation equivalents were less effective masks than different-language, unrelated masks but were similar to subordinate same-language masks. The results suggest that the relationship between the representations of translation equivalents is similar to that between same-language superordinate and subordinate words.

Adult↗
PubMed1976

Thyroid dysfunction in uremia: evidence for thyroid and hypophyseal abnormalities.

Disturbances in thyroid function and a high prevalence of goiter develop in patients on chronic hemodialysis. This study shows that in patients on dialysis, mean serum thyroxine and triiodothyronine levels are lower than normal. Patients with chronic renal failure not on dialysis, have mean serum thyroxine levels similar to normal subjects and low mean serum triiodothyronine levels. However, both serum thyroxine and triiodothyronine concentrations decrease as the renal failure worsens. In addition, both groups of patients with renal failure have a decreased serum thyroxine response to oxogenous thyrotrophin and a diminished serum thyrotrophin response to thyrotrophin-releasing hormone. These data suggest the presence of an intrathyroidal and an hypophyseal defect in uremic patients. Although serum iodide concentrations are elevated, there is no correlation between the level of serum iodide and the degree of renal failure. Therefore, we have no direct evidence that iodide excess is responsible for the abnormalities observed.

Adolescent↗