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Biomedical subjects

R S Gibson

Publications and source records attributed to R S Gibson.

At least 163 records · Page 9Linked to original sources
PubMed1982

Clinical implications of increased lung uptake of thallium-201 during exercise scintigraphy 2 weeks after myocardial infarction.

To determine the prevalence and clinical significance of increased lung thallium-201 uptake during submaximal exercise myocardial scintigraphy performed 2 weeks after acute myocardial infarction, 61 patients underwent submaximal exercise testing (target heart rate, 120 beats/min), multigated blood pool imaging at rest and coronary angiography before hospital discharge. Thallium lung uptake on the initial anterior projection image was graded qualitatively by comparing the intensity of thallium-201 activity in the lungs with that in the mediastinum. In 39 patients (64 percent), it was normal (equal to mediastinal activity) and in 22 (36 percent), it was increased (greater than mediastinal activity). Compared with patients with normal lung uptake, those with increased uptake had a greater prevalence of prior infarction (13 versus 36 percent, probability [p] less than 0.05), less global cardiac reserve as assessed by the four level New York Heart Association classification (p less than 0.05), more advanced Killip class in the coronary care unit (p less than 0.05), a higher Norris coronary prognostic index (2.6 +/- 1.9 versus 4.6 +/- 2.3 [mean +/- standard deviation], p less than 0.01), failure to achieve the target heart rate because of dyspnea, fatigue or angina (36 versus 86 percent, p less than 0.01), a greater prevalence of exercise-induced S-T segment depression (18 versus 45 percent, p less than 0.05), a greater number of anterior thallium-201 myocardial defects (p less than 0.05); a lower radionuclide ejection fraction at rest (50.4 +/- 6.1 versus 39.6 +/- 9.3 percent, p less than 0.01) and a greater number of asynergic left ventricular segments (p less than 0.05). Thus, the occurrence of increased lung thallium-201 uptake during submaximal exercise scintigraphy in the early postinfarction period is frequent and appears to be a marker of severe and functionally more important coronary artery disease associated with left ventricular dysfunction.

Aged↗
PubMed1982

Changes in hair arsenic levels in breast and bottle fed infants during the first year of infancy.

Hair samples were collected from 13 breast fed and 19 bottle fed infants at one, three, six and twelve months of age. Food frequency data were also collected. Arsenic and antimony concentrations determined in washed hair samples by neutron activation procedures, rose significantly with age, the highest levels being evident at twelve months. Hair arsenic and antimony levels were independent of sex, and method of milk feeding. However, at twelve months, the median hair arsenic level for those infants receiving cereal at six months of age (0.655 microgram/g) was significantly higher (p = 0.05) than for those infants fed exclusively a milk based diet at this time (median = 0.225 microgram/g). Recent data show that cereals are major dietary sources of arsenic during infancy. Hence findings of this study suggest that changes in hair arsenic levels during infancy are related to the introduction of cereals in the diet.

Age Factors↗
PubMed1982

Trace element intakes of women.

1. Energy, protein, zinc, copper, manganese, selenium and dietary fibre intakes of 100 pre-menopausal women (mean age 30.0 +/- 6.1 years) from a university community, and consuming self-selected diets, were calculated using 3 d dietary records and food composition values. Subjects also collected a 24 h food composite during the 3 d record period for analysis of Zn, Cu and Mn by atomic absorption spectrophotometry. Daily analysed intakes were compared with those calculated from the corresponding record day. 2. Mean daily calculated intakes of energy, protein, Zn, Cu, Mn, Se and dietary fibre were 7.54 +/- 1.61 MJ, 74 +/- 18 g protein, 10.1 +/- 3.3 mg Zn, 1.9 +/- 0.6 mg Cu, 3.1 +/- 1.5 mg Mn, 131 +/- 53 micrograms Se, 19.4 +/- 6.6 g dietary fibre. 3. Major food sources for each of the trace elements were (%): Zn meat + substitutes 43, dairy products 23.7; Cu breads and cereals 22, vegetables 21; Mn breads and cereals 47, fruits 12, Se meat + substitutes 38, breads and cereals 30. 4. Highly significant correlations (P = 0.001) were noted for analysed intakes of Zn, Cu and Mn and those calculated from the corresponding record day. Mean calculated intakes were higher (%): Zn 138, Cu 142, Mn 121, than corresponding mean analysed intakes (P = 0.01). However, the mean nutrient densities (mg/MJ) were comparable: Zn analysed 1.2, calculated 1.4; Cu analysed 0.2, calculated 0.2; Mn analysed 0.4, calculated 0.4. 5. All subjects met the Canadian Dietary Standard (CDS) recommended level for Cu but 48% received less than the CDS for Zn, 6% obtaining less than two-thirds of this recommended level. Daily Mn and Se intakes were similar to recent values for North American diets.

Adult↗
PubMed1982

Changes in hair zinc and copper concentrations of breast fed and bottle fed infants during the first six months.

A longitudinal study of 35 full term breast fed (20 males and 15 females; mean birthweight = 3540 g) and 25 full term bottle fed infants (14 males and 11 females; mean birthweight = 3466 g) was carried out to compare the effect of method of feeding on hair zinc and copper concentrations. Hair samples were collected at 30 +/- 2, 90 +/- 4 and 180 +/- 4 days of age and analysed for zinc and copper by instrumental neutron activation procedures. Mean daily zinc and copper intakes were calculated at monthly intervals using three day diet records and test weigh data for the breast fed group. Only the male bottle fed infants showed a significant decline in hair zinc concentration (p less than 0.01) during the six-month study period. These results support the suggestion that male infants have a higher requirement for zinc than females in early infancy. No comparable systematic decline in hair zinc levels was evident in the female bottle fed infants or the male and female breast fed infants. The absence of any fall in hair zinc concentrations in the breast fed infants, despite their significantly lower (p less than 0.01) dietary zinc intakes compared to the bottle fed group, is attributed to the superior bioavailability of zinc from breast milk. Hair copper levels rose during the first three months in both groups, subsequently declining between 3-6 months. These changes were not significantly related to sex or method of milk feeding, but are associated with the redistribution of copper which occurs during early infancy.

Bottle Feeding↗
PubMed1982

Precordial ST-segment depression during acute inferior myocardial infarction: clinical, scintigraphic and angiographic correlations.

The cause and associated pathophysiology of precordial ST-segment depression (ST decreases) during acute inferior myocardial infarction (IMI) are controversial. To investigate this problem, electrocardiographic findings in 48 consecutive patients with acute IMI were prospectively compared with results of coronary angiography, submaximal exercise thallium-201 (201TI) scintigraphy and multigated blood pool imaging, all obtained 2 weeks after IMI, and with clinical follow-up at 3 months. Patients were classified according to the admission ECG obtained 3.3 +/- 3.1 hours after the onset of chest pain. Twenty-one patients (group A) had no or less than 1.0 mm ST decreases, and 27 (group B) had greater than or equal to 1.0 mm ST decreases in two or more precordial (V1-6) leads. Patients in group B had more prolonged chest pain after admission to the coronary care unit than those in group A (2.8 +/- 3.0 vs 1.2 +/- 1.1 hours, p less than 0.03), greater summed ST-segment elevation in leads II, III, aVF (6.7 +/- 4.7 vs 3.3 +/- 4.5 mm, p less than 0.02), higher plasma peak creatine kinase levels (1133 +/- 781 vs 653 +/- 482 IU/l, p less than 0.01), a higher prevalence of "true posterior" infarction by ECG criteria (26% vs 5%, p less than 0.05), a lower radionuclide ejection fraction (46 +/- 9% vs 54 +/- 6%, p less than 0.001), more extensive infarct-related asynergy (p less than 0.001) and 201TI perfusion abnormalities (p less than 0.01), more complications during hospitalization (p less than 0.03), and more cardiac events at 3 months (p less than 0.02). There were no significant differences between group A and group B in the extent of underlying coronary disease, prevalence of left anterior descending coronary artery disease, exercise-induced ST decreases or angina, and 201TI defects or wall motion abnormalities in anterior or septal segments. Thus, patients with acute IMI who have associated precordial ST decreases have greater global and regional left ventricular dysfunction due to more extensive inferior or inferoposterior wall infarction, rather than concomitant anteroseptal ischemic injury.

Angina Pectoris↗
PubMed1981

Prolonged QT interval at onset of acute myocardial infarction in predicting early phase ventricular tachycardia.

The prospectively assessed time course of changes in ventricular repolarization during acute myocardial infarction (AMI) is reported in 32 patients admitted 2.0 +/- 1.8 (SD) hours after AMI onset. The initial corrected QT interval (QTc) upon hospitalization was longer (0.52 +/- 0.07 seconds) in the 14 patients developing ventricular tachycardia (VT) within the first 48 hours as compared to QTc (0.47 +/- 0.03 seconds) in the eight patients with frequent ventricular premature beats (VPBs) and to QTc (0.46 +/- 0.03 seconds) in the 10 patients with infrequent VPBs (p less than 0.001; analysis of variance). By the fifth day after AMI onset, the QTc shortened significantly only in the VT group, suggesting a greater initial abnormality of repolarization in these patients. All 32 patients had coronary angiography, radionuclide ventriculography, and myocardial perfusion scintigraphy before hospital discharge. Significant discriminating factors related to early phase VT in AMI included initially longer QT and QTc intervals, faster heart rate, higher peak serum levels of creatine kinase, acute anterior infarction, angiographically documented proximal stenosis of the left anterior descending coronary artery, and scintigraphic evidence of hypoperfusion of the interventricular septum. Prior infarction, angina pectoris, hypertension, multivessel coronary artery disease, and depressed left ventricular ejection fraction did not provide discrimination among the three different ventricular arrhythmia AMI groups. We conclude that (1) the QT interval is frequently prolonged early in AMI, (2) the initial transiently prolonged ventricular repolarization facilitates and predicts complex ventricular tachyarrhythmias within the first 48 hours of AMI, (3) jeopardized blood supply to the interventricular septum frequently coexists, and (4) therapeutic enhancement of rapid recovery of the ventricular repolarization process merits investigation for prevention of VT in AMI.

Acute Disease↗
PubMed1981

Role of two-dimensional echocardiography in the evaluation of patients with ventricular septal rupture postmyocardial infarction.

In 18 consecutive patients with a new murmur following acute myocardial infarction (AMI), examination by two-dimensional echocardiography (2DE) correctly excluded ventricular septal defects (VSD) in eight patients and enabled direct visualization of the VSD in 10 patients. In three patients, 2DE was the first technique to establish the diagnosis. In all patients with VSD, 2DE diagnosis was confirmed by catheterization, surgery, and/or postmortem examination. In six patients with VSD, 2DE contrast studies were performed and were positive. 2DE enabled localization of the VSD in all patients (five inferior, five anterior). To evaluate left ventricular (LV) function, a 2DE wall motion index (WMI) was calculated using an 11 segment model of the LV. While there was no difference (p greater than 0.2) in AMI-VSD survivors versus nonsurvivors in age, kinase, and AVO2 difference, there was no overlap in WMI (p = 0.004) of survivors (0.80 +/- 0.36) versus nonsurvivors (1.66 +/- 0.19). Thus 2DE allows accurate detection and localization of postmyocardial infarction VSD and enables determination of prognosis of these patients.

Acute Disease↗
PubMed1981

Predicting the extent and location of coronary artery disease during the early postinfarction period by quantitative thallium-201 scintigraphy.

The ability of quantitative thallium-201 scintigraphy to predict the extent and location of coronary artery disease before hospital discharge after acute myocardial infarction was evaluated in 52 patients. All patients underwent coronary angiography and serial thallium-201 imaging either at rest (10 patients) or after submaximal exercise stress (42 patients; target heart rate 120 beats/min). Two or three vessel disease was designated if abnormal thallium-201 uptake or washout patterns, or both, were seen in two or three vascular segments, respectively. Of 156 vessels analyzed in the 52 patients, 91 stenoses of 70 percent or greater were found by angiography. Seventy-four (81 percent) of these were predicted by scintigraphy. The specificity of scintigraphy for identifying vessel stenoses was 92 percent. Sensitivity for detecting and localizing stenoses supplying an infarct zone was 96 percent compared with 62 percent for stenoses supplying myocardium remote from the acute infarct. Perfusion abnormalities were more frequently seen in the distribution of vessels with severe (90 percent or greater) stenoses than in those with moderate (70 to 90 percent) stenoses (87 versus 53 percent, p less than 0.01). Scintigraphy detected a greater proportion of left anterior descending and right coronary arterial stenoses than circumflex stenoses (91 and 87 versus 63 percent, respectively, p less than 0.006). In the 42 patients who underwent submaximal exercise testing, multivariate analysis of 23 clinical and laboratory variables identified multiple thallium-201 defects as the best predictor of multivessel disease. The predictive accuracy of exercise-induced S-T segment depression was only 45 percent compared with 88 percent (p less than 0.05) for thallium-201 scintigraphy. Thus, 2 weeks after myocardial infarction, exercise thallium-201 scintigraphy is useful for predicting the extent and location of coronary artery disease, particularly stenoses in the left anterior descending and right coronary arteries. Moreover, thallium-201 imaging at rest is reliable in assessing the extent of coronary disease in hospitalized patients who cannot undergo exercise testing because of unstable angina, uncompensated heart failure, poorly controlled arrhythmias or physical limitations.

Adult↗
PubMed1981

The iron and zinc status of long-term vegetarian women.

Iron and zinc status of 56 Seventh-Day Adventist Canadian women (mean age 52.9 +/- 15.3 yr) following vegetarian diets for 19 +/- 17 yr were investigated. Energy, protein, iron, available iron, zinc, and total dietary fiber intakes were calculated from 3-day dietary records. Hemoglobin, serum iron, total iron binding capacity, serum and hair zinc concentrations were also determined. Plant products provided 92 and 77% of the total dietary iron and zinc intakes, respectively. Calculated mean daily intakes (+/- SD) for energy, protein, iron, zinc, and total dietary fiber were 1630 +/- 354 kcal, 58 +/- 14 g, 12.5 +/- 3.0 mg, 9.2 +/- 2.5 mg, and 30.9 +/- 11.0 g, respectively. Mean hemoglobin (13.1 +/- 1.0 g/dl), calculated serum transferrin saturation (37.5 +/- 12.9%), mean serum zinc (99 +/- 24 microgram/dl), and hair zinc concentrations (187 +/- 44 ppm) were all within the normal range. The iron and zinc status of these long-term Seventh-Day Adventist vegetarian women appeared adequate despite their low intake of readily absorbed iron and zinc from flesh foods and their high intake of total dietary fiber and phytate.

Adult↗
PubMed1981

Changes in serum zinc concentrations of some Canadian full term and low birthweight infants from birth to six months.

Serum samples were collected from 99 infants at birth, and when they were 1, 3 and 6 months old. Thirty-seven were preterm infants with a mean birthweight of 1880 g and 26--36 wk gestation; 24 were full term low birthweight with a mean birthweight of 2371 g and 38--42 wk gestation; and 38 were full term normal birthweight infants with a mean birthweight of 3590 g and 38--42 wk gestation. Serum zinc concentrations were determined by instrumental neutron activation procedures. No significant differences in serum zinc levels were apparent between sexes or among the 3 groups. Levels were highest at birth and declined during the first 3 months. Between 3 and 6 months, serum zinc levels remained fairly constant, and were lower than reported levels for North American adults. It is concluded that the decline in serum zinc concentration in all three groups was not significantly correlated with birthweight or gestational age and the low birthweight infants in this study did not show any evidence of zinc deficiency. The general decline in serum zinc levels appeared to be associated with low dietary zinc intakes.

Female↗
PubMed1981

Spatial and temporal quantitation of plane thallium myocardial images.

A computer method has been developed to determine the relative initial uptake and segmental washout rates of thallium-201 from sequential myocardial images. Initial images in multiple projections are obtained at 10 min after thallium-201 injection, and delayed images 2-3 hr after injection. A modified interpolative method was used to construct a background reference plane, and net myocardial counts was used to construct a background reference plane, and net myocardial counts above this reference plane were determined from multiple count profiles. Washout rates were determined by linear regression of time-activity curves constructed from the sequential images. In this approach, both relative temporal as well as relative spatial quantitation is performed. Data from 25 normal subjects were used to establish numerical criteria and normal ranges for relative focal defects and abnormal segmental washout slopes. Normal ranges were set to include the 90-percentile limits of the distribution of values obtained from the normal population. From these values we derived a quantitative criterion for thallium scan interpretation that can be used for analysis and interpretation of scintigrams in clinical situations.

Adult↗
PubMed1980

Hair as a biopsy material for the assessment of trace element status in infancy. A review.

Results of the studies reviewed suggest that hair represents a promising biopsy material to study trace element redistribution and changes in trace-element status during early infancy. Caution must be exercised in sampling and only proximal, recently-grown hair collected. Appropriate standard washing procedures must also be employed and sensitive analytical techniques used for the determination of hair trace element concentrations.

Adolescent↗