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Biomedical subjects

R S Gibson

Publications and source records attributed to R S Gibson.

At least 127 records · Page 7Linked to original sources
PubMed1987

Doppler measurement of left atrial depressurization and mitral valve area in patients with suspected mitral stenosis: validation of a new method.

Atrial depressurization time measurement by Doppler ultrasound can be used to quantify stenotic mitral valve area. In this report, we present the results of a blinded trial comparing the standard Doppler method for "pressure half-time" (A) and another Doppler method we devised (B) for measurement of atrial depressurization time. Both methods were tested against valve area data from catheterization performed within 24 hours after Doppler echocardiography. Ten readers analyzed each of 10 Doppler profiles by methods A and B, in random order. After decoding, each of the 200 Doppler readings was compared to the catheterization result. Method B proved more accurate than method A by repeated measures analysis of variance (p less than 0.0001). Furthermore, method B took less than half as long to perform (p less than 0.0001). The methods presented herein provide a simple alternative means to follow the progression of mitral stenosis noninvasively and to determine optimal timing for surgery.

Heart Atria↗
PubMed1987

A prospective comparison of continuous wave versus high pulse repetition frequency Doppler echocardiography for quantifying transvalvular pressure gradients in adults with aortic stenosis.

To evaluate the relative accuracy of continuous wave (CW) and high pulse repetition frequency (HPRF) Doppler for estimating aortic transvalvular pressure gradients, Doppler examinations with both devices were obtained in 87 consecutive patients with aortic valve disease. Thirty-seven (43%) also underwent catheterization and direct determination of the pressure gradient. The correlation between CW Doppler and catheterization measurements was high (r = 0.91) and significantly superior to HPRF Doppler (r = 0.72; p less than 0.005). Disparities between the Doppler measurements predominantly occurred in patients with gradients exceeding 50 mm Hg in whom underestimation by the HPRF instrument was frequent. These data suggest that continuous wave Doppler is the preferred modality for the estimation of transvalvular pressure gradients in adult patients with moderate or severe aortic stenosis.

Adult↗
PubMed1987

Acute non-Q wave myocardial infarction associated with early ST segment elevation: evidence for spontaneous coronary reperfusion and implications for thrombolytic trials.

The clinical significance of early ST segment elevation in patients with non-Q wave infarction is unknown. Therefore, 150 consecutive patients with creatine kinase isoenzyme-confirmed acute uncomplicated myocardial infarction who had ST segment elevation of 1 mm or more in at least two contiguous leads on the admission electrocardiogram were analyzed. None received thrombolytic therapy or acute coronary angioplasty. Predischarge angiography, radionuclide ventriculography and exercise thallium-201 scintigraphy were performed 10 +/- 3 days after myocardial infarction. Based on serial electrocardiograms (on days 1, 2, 3 and 10), all 150 infarcts were classified as Q wave (n = 115 [77%]) or non-Q wave (n = 35 [23%]). Although patients with Q wave infarction exhibited greater ST elevation, the amount observed in the non-Q wave group was appreciable, as reflected by the number of leads with ST elevation (3.8 +/- 1.8 versus 3.1 +/- 1.2, p = 0.007) and the sum of the ST elevation (9.6 +/- 7.4 versus 6.2 +/- 6.2 mm, p = 0.016). When compared with the Q wave group, patients with non-Q wave infarction had a shorter time to peak creatine kinase (23.0 +/- 9.1 versus 15.8 +/- 7.9 hours, p = 0.0001), a higher infarct vessel patency rate (24 versus 57%, p = 0.001), lower peak creatine kinase values based on 4 hour sampling (1,372 +/- 964 versus 664 +/- 924 IU/liter, p = 0.0002) and a higher left ventricular ejection fraction (46 +/- 12% versus 54 +/- 9%, p = 0.0003).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Exercise-induced ST segment elevation 2 weeks after uncomplicated myocardial infarction: contributing factors and prognostic significance.

To define the prevalence and clinical significance of exercise-induced ST segment elevation during predischarge treadmill testing after uncomplicated acute myocardial infarction confirmed by serum MB creatine kinase (CK) activity, 241 consecutive patients were prospectively investigated with quantitative exercise thallium-201 scintigraphy, rest radionuclide ventriculography and coronary angiography at 10 +/- 3 days. All patients received customary care, and in none was thrombolytic therapy or emergency coronary angioplasty employed. Eighty-two patients (34%) had exercise-induced ST segment elevation of greater than or equal to 1 mm above rest baseline. These patients were similar to the 159 patients without this finding with respect to history of prior infarction, the Norris coronary prognostic index, exercise duration, metabolic equivalents (METs) achieved and peak heart rate-blood pressure product. The frequency of inducible myocardial ischemia and extent of angiographic coronary disease was also comparable in the two groups. Findings associated with larger infarct size and transmural extent of infarction were more common in patients with exercise-induced ST segment elevation than in those without, including higher peak CK values (1,235 +/- 1,037 versus 942 +/- 915 mumol/min per liter, p less than 0.026), lower left ventricular ejection fraction (43 +/- 12 versus 51 +/- 10%, p less than 0.001), a higher prevalence of pathologic Q waves in greater than or equal to 2 contiguous infarct-related leads (80 versus 55%, p less than 0.001), more persistent thallium-201 defects (2.2 +/- 1.1 versus 1.4 +/- 1.1, p less than 0.001), abnormally increased lung uptake of thallium (33 versus 18%, p less than 0.01) and a greater number of akinetic or dyskinetic segments (3.2 +/- 2.5 versus 1.4 +/- 1.9, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1987

The vitamin D status of East Indian Punjabi immigrants to Canada.

1. Serum 25-hydroxyvitamin D (25-OHD), calcium and alkaline phosphatase (EC 3.1.3.1) levels and vitamin D intakes (from 3 d weighed dietary records) were determined in a cohort of fifty-nine male East Indian Punjabi immigrants (37.7 (SD 10.5) years) and fifty-four females (33.3 (SD 7.4) years). 2. Females had somewhat lower mean serum 25-OHD levels (12.3 (SD 5.0) v. 14.2 (SD 5.1) ng/ml, P less than 0.05) and serum Ca levels (88 (SD 8) v. 91 (SD 6) mg/l) than males (P less than 0.05) whereas serum alkaline phosphatase values (males 167 (SD 63), females 169 (SD 43) IU/l) and dietary vitamin D intakes (males 3.5 (SD 1.8), females 3.3 (SD 2.0) micrograms/d) were similar. 3. 22% of the females and 12% of the males had serum 25-OHD levels below 9.0 ng/ml but none had serum 25-OHD levels within the range associated with clinically overt disease. 4. In the males, serum 25-OHD levels were negatively correlated with dietary fibre intakes (g/d; r -0.29; P less than 0.05). 5. Multiple-regression analysis indicated that log serum 25-OHD levels were not related to dietary vitamin D intakes. Instead they were associated with sex and dietary fibre intakes (g/MJ) (F 3.71; P = 0.03). These two variables explained 8% of the variance.

Adult↗
PubMed1987

Food consumption patterns of Canadian preschool children in relation to zinc and growth status.

Hair and serum zinc and copper, growth percentiles, and dietary intakes, based on 3-day weighed food records, were determined for 106 Canadian preschool children (62 M, 44 F) aged 4-5 yr. Mean (+/- SD) hair zinc levels were (M) 103 +/- 35 micrograms/g vs (F) 129 +/- 34 micrograms/g, p less than 0.001, and median hair copper level was 12.4 micrograms/g (M + F). Mean serum zinc and copper were 111 +/- 13 micrograms/dL (M + F) and 122 +/- 21 micrograms/dL (M + F), respectively. Males with low hair zinc (less than 70 micrograms/g) had a lower mean height-for-age percentile (42 +/- 29 vs 58 +/- 25%, p less than 0.05), even when adjusted for midparent height. Males with hair zinc less than 70 micrograms/g and/or height-for-age less than 15% consumed less meat, poultry, and fish and received similar average zinc intakes but higher calcium intakes than males with hair zinc greater than or equal to 70 micrograms/g and/or height-for-age greater than or equal to 15%. Suboptimal zinc nutriture was associated with lower intakes of readily available zinc from flesh foods and higher intakes of calcium.

Canada↗
PubMed1987

Hypertrophic cardiomyopathy and myocardial ischemia with normal coronary arteries.

The case reported herein illustrates an unusual form of nonobstructive hypertrophic cardiomyopathy which was associated with Wolff-Parkinson-White syndrome, myocardial ischemia and necrosis despite normal coronary arteries. The patient is unique since the hypertrophied myocardial segment was localized exclusively to the posterolateral free wall. Quantitative thallium-201 scintigraphy demonstrated reversible ischemia that corresponded precisely with this region of posterolateral hypertrophy. While the exact mechanism for ischemia in patients with hypertrophic cardiomyopathy and normal coronary arteries remains controversial, a functional rather than anatomic disturbance of blood flow seems likely.

Adolescent↗
PubMed1987

Serum and urine chromium as indices of chromium status in tannery workers.

Serum and urinary Cr levels of a selected group of men exposed to CrIII in four Southern Ontario tanneries were compared with those of men not exposed to Cr. Fasted blood samples were obtained from 72 tannery workers (TW; mean age +/- SD = 36 +/- 12 years) and from 52 controls (CS; mean age +/- SD = 41 +/- 13 years). Serum Cr levels as determined by graphite furnace atomic absorption spectrophotometry were significantly higher (P = 0.0001) for TW (median 0.49 ng/ml, range 0.37-0.81) than for CS (median 0.15 ng/ml, range 0.12-0.20). Urine samples were collected from 49 TW and 43 CS on a Friday pm and from 42 TW on a Monday am. Urinary creatine (Cre) was determined by the Jaffe reaction. For Friday samples, the median urinary Cr/Cre ratio was significantly higher (P = 0.0001) for TW (median 0.83 ng/mg, range 0.48-1.82) than for CS (median 0.18 ng/mg, range 0.13-0.26). For TW, Cr/Cre was correlated with serum Cr (r = 0.72, P = 0.0001). Neither urinary Cr/Cre nor serum Cr was correlated with length of employment in the tanning industry. There were significant differences in serum Cr levels and urinary Cr/Cre ratios among TW employed in different areas of the tanneries. For TW, the median urinary Cr/Cre ratio for Monday morning samples was significantly lower than for Friday afternoon samples (P = 0.03). These data indicate that CrIII is absorbed and that serum and urine Cr in tannery workers may be indices of Cr exposure and status.

Adult↗
PubMed1987

Clinical, functional, and angiographic distinctions between Q wave and non-Q wave myocardial infarction: evidence of spontaneous reperfusion and implications for intervention trials.

We prospectively evaluated 241 consecutive patients with creatine kinase (MB fraction)-confirmed acute myocardial infarction with predischarge quantitative thallium-201 scintigraphy, coronary angiography, radionuclide ventriculography, and 24 hr Holter monitoring. Based on serial electrocardiograms, 154 patients had Q wave (QMI) and 87 had non-Q wave (NQMI) infarction. Despite less myocardial necrosis and better left ventricular function, the NQMI group had the same long-term survival as the QMI group. During 27 months of follow-up, patients with NQMI experienced more reinfarctions (p = .009), had a higher rate of unstable angina pectoris requiring rehospitalization (p = .034), and had a greater likelihood of subsequent bypass surgery or angioplasty (p = .018). Based on our thallium scintigraphic data, the greater clinical instability after NQMI appeared to be related to the presence of a larger residual mass of viable but jeopardized myocardium within the perfusion zone of the infarct-related vessel. Our results also indicate that the pathogenesis of NQMI may involve early spontaneous reperfusion and that patients with NQMI can experience sudden death despite well-preserved left ventricular function.

Coronary Angiography↗
PubMed1986

Diltiazem and reinfarction in patients with non-Q-wave myocardial infarction. Results of a double-blind, randomized, multicenter trial.

We performed a multicenter, double-blind, randomized study to evaluate the effect of diltiazem on reinfarction after a non-Q-wave myocardial infarction. Nine centers enrolled 576 patients: 287 received diltiazem (90 mg every six hours) and 289 received placebo. Treatment was initiated 24 to 72 hours after the onset of infarction and continued for up to 14 days. The primary end point, reinfarction, was defined as an abnormal reelevation of MB creatine kinase in plasma within 14 days. Reinfarction occurred in 27 patients in the placebo group (9.3 percent) and in 15 in the diltiazem group (5.2 percent)--a 51.2 percent reduction in cumulative life-table incidence (P = 0.0297; 90 percent confidence interval, 7 to 67 percent). Diltiazem reduced the frequency of refractory postinfarction angina (a secondary end point) by 49.7 percent (P = 0.0345; 90 percent confidence interval, 6 to 73 percent). Mortality was similar in the two groups (3.1 and 3.8 percent, respectively, in the placebo and diltiazem groups), but adverse drug reactions (most of which were mild) were more common in the diltiazem group. Nevertheless, the drug was well tolerated, despite concurrent treatment with beta-blockers in 61 percent of the patients. We conclude that diltiazem was effective in preventing early reinfarction and severe angina after non-Q-wave infarction and that it was also safe and generally well tolerated.

Aged↗
PubMed1986

Iron status of predominantly lacto-ovo vegetarian East Indian immigrants to Canada: a model approach.

Iron status of East Indian predominantly lacto-ovo vegetarian immigrants (59 males, mean age 37.7 +/- 10.5 yr; 55 females, mean age 33.3 +/- 7.4 yr) was assessed using dietary and biochemical-iron indices, including a Tri-index (TI) model. Iron deficiency was higher among females than males: 33% vs 5%, respectively, via the TI model (serum ferritin, serum-transferrin saturation, and mean corpuscular-hemoglobin concentration) and 18-42% vs 2-22%, respectively, via individual biochemical-iron indices. Rates of anemia calculated via the TI model in combination with low hemoglobin and mixed-distribution analysis (MDA) were similar and higher for the females (TI + Hb = 16%; MDA = 12%) than for the males (TI + Hb = 5%; MDA = 3%). High prevalence among females was attributed to low available iron intakes, concomitant with high intakes of dietary fiber, phytate, and tannins. We recommend the TI-model approach to estimate relative prevalence of iron deficiency in small surveys.

Adult↗
PubMed1986

The prevalence and clinical significance of residual myocardial ischemia 2 weeks after uncomplicated non-Q wave infarction: a prospective natural history study.

Despite having smaller infarct size and better left ventricular function, patients with non-Q wave myocardial infarction (NQMI) appear to have an unexpectedly high long-term mortality that is ultimately comparable to that of patients with Q-wave myocardial infarction (QMI). Patients with NQMI may lose their initial prognostic advantage because there is more viable tissue in the perfusion zone of the infarct-related vessel, rendering myocardium more prone to reinfarction. We tested this hypothesis in a prospective study of 241 consecutive patients 65 years of age or younger with acute uncomplicated myocardial infarction confirmed by creatine kinase levels (MB fraction). All patients received customary care and none underwent thrombolytic therapy or emergency angioplasty. Predischarge coronary angiography, radionuclide ventriculography, 24 hr Holter monitoring, and quantitative thallium-201 (201T1) scintigraphy during treadmill exercise were performed 10 +/- 3 days after infarction. Infarcts were designated as QMI (n = 154) or NQMI (n = 87) by accepted criteria applied to serial electrocardiograms obtained on days 1, 2, 3, and 10. The baseline Norris coronary prognostic index, angiographic jeopardy scores, and prevalence of Lown grade ventricular arrhythmias were similar between groups despite evidence for less necrosis with NQMI vs QMI, reflected by lower peak creatine kinase levels (520 vs 1334 IU/liter; p = .0001, 4 hr sampling), higher resting left ventricular ejection fraction (53% vs 46%; p = .0001), fewer akinetic or dyskinetic segments (1.2 vs 2.4; p = .0001), and fewer persistent 201Tl defects in the infarct zone (0.9 vs 1.9; p = .0001). Patients with NQMI also had more patent infarct-related vessels (54% vs 25%; p less than .0001) and a shorter time from onset of infarction to peak creatine kinase level (16.9 vs 22.5 hr; p = .0001). Importantly, the prevalence and extent of quantitatively determined 201Tl redistribution within the infarct zone on exercise scintigraphy was greater in patients with NQMI vs those with QMI (60% vs 36%, p = .007; and 0.98 vs 0.53 myocardial segments, p = .0003); when the two groups were stratified on the basis of the infarct-related vessel, subset analysis revealed the same findings. During 30 months median follow-up, cardiac mortality was low, 8.4% in the QMI group and 9.2% in the NQMI group (p = NS).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Postinfarction ventricular septal rupture: the importance of location of infarction and right ventricular function in determining survival.

Over a 5.5 year period, 1264 consecutive patients with acute myocardial infarction as confirmed by enzyme levels were prospectively identified. Of these, 25 (2%) suffered ventricular septal rupture (pulmonary/systemic flow range 1.5 to 6) 7 +/- 7 days after onset of myocardial infarction. Death occurred in 14 patients (56%) and was more common after inferior than anterior myocardial infarction (11 of 15 [73%] vs three of 10 [30%], p less than .05). Among 133 variables analyzed, survivors and nonsurvivors were similar with respect to all premorbid clinical characteristics, infarct size as assessed by peak creatine kinase values, shunt size, two-dimensional echocardiographic and hemodynamic indexes of left ventricular function, and extent of coronary disease. Compared with survivors, the nonsurvivors had greater impairment of right ventricular function as determined by a higher two-dimensional echocardiographically derived right ventricular wall motion index (RVWMI) (0.55 +/- 0.87 vs 1.70 +/- 0.45, p less than .001), greater elevation of right ventricular end-diastolic pressure (11 +/- 6 vs 17 +/- 6, p less than .02), and greater mean right atrial pressure (10 +/- 6 vs 16 +/- 3, p less than .01). Of interest, two of the three patients who presented with anterior myocardial infarction and who died had inferiorly extended infarcts and all had abnormal RVWMIs (greater than or equal to 1.0). As expected, cardiogenic shock shortly after onset of ventricular septal rupture was associated with a 91% mortality, but was more common after inferior than anterior myocardial infarction (60% vs 20%, p less than .05). The mean effective cardiac index was also higher in survivors than nonsurvivors (2.1 +/- 0.5 vs 1.2 +/- 0.5, p less than .001). Finally, multivariate analysis indicated that all nonsurvivors could be identified based on: an effective cardiac index of 1.75 liters/min/m2 or less, the presence of extensive right ventricular and septal dysfunction on the two-dimensional echocardiogram, a mean right atrial pressure of 12 mm Hg or more, and early onset of ventricular septal rupture. Thus, our data demonstrate that: mortality is higher when ventricular septal rupture complicates inferior than when it complicates anterior myocardial infarction, survivors can be distinguished from nonsurvivors and the prediction of outcome is highly accurate, and combined right ventricular and septal dysfunction has a substantial impact on prognosis.

Adult↗
PubMed1986

Evaluation of postoperative flow reserve in internal mammary artery bypass grafts.

The internal mammary artery has been advocated for use in bypass grafting owing to its superior long-term patency when compared to saphenous vein grafts. Concern exists that the flow through the internal mammary artery may be inadequate during periods of peak myocardial demand. This flow was investigated in 24 consecutive patients with a mean proximal left anterior descending artery stenosis of 87.5% who were selected for coronary bypass using the internal mammary artery. Within 8 weeks of operation, all were evaluated by exercise thallium 201 scintigraphy. Thallium activity, expressed as a ratio of anteroseptal activity to posterolateral wall activity (or inferior wall activity if the posterolateral wall was deemed abnormal), was 0.97 +/- 0.15. A second group of 25 patients, with normal coronary arteries, was similarly evaluated. The mean septal to posterolateral wall thallium activity ratio for these control patients was 1.0 +/- 0.15. A third group of 26 patients who underwent single-vessel percutaneous transluminal coronary angioplasty of the left anterior descending artery and a fourth group of 28 saphenous vein graft recipients were compared by stress thallium scintigraphy. Thallium 201 activity for the vein graft group (0.96 +/- 0.19) was not significantly different from that for the mammary artery group, whereas the flows obtained with a single attempt at angioplasty were significantly inferior (p less than 0.05). The internal mammary artery provides excellent coronary flow at peak myocardial demand and compares favorably to angioplasty and saphenous vein grafting.

Angioplasty, Balloon↗
PubMed1986

A study of seasonal trace element intakes and hair trace element concentrations in selected households from the Wosera, Papua New Guinea.

The trace element status of nine households from the Wosera subdistrict of Papua New Guinea was assessed. Individual weighed three-day dietary intakes were carried out in April during the hungry season when yams were not eaten and in July when yams were available. Representative staple food items analyzed 'as eaten' for energy, protein, Ca, Mn, Cu and Zn and mean daily energy and nutrient intakes calculated. Hair samples were also collected in July, washed, and analyzed for Zn, Cu and Mn by INAA. Seasonal differences in energy, protein, Ca, Fe and Mn intakes were related to changes in yam consumption. The Zn status of the male (M) and female (F) adults and children (Ch) was sub-optimal based on low median hair Zn levels (microgram/g): -F = 78, n = 8; M = 108, n = 8; Ch2-4yrs = 79, n = 8; Ch5-10yrs = 94, n = 7 and inadequate intakes of readily available Zn (mean + SD): - April M + F = 7.0 + 1.6 mg/day; July M + F = 8.2 + 1.5 mg/day; less than three percent Zn from animal products. In contrast their Mn status, as indicated by elevated median hair Mn levels (microgram/g) (F = 25.1; M = 26.3; Ch2-4yrs = 21.5; Ch5-10yrs = 15.2) was high, attributed to elevated Mn intakes (April M + F = 11.0 + 2.2 mg/day; July M + F = 7.5 + 1.4 mg/day). Median hair Cu levels (microgram/g) (F = 7.6; M = 7.5; Ch2-4yrs = 8.6; Ch5-10yrs = 7.8) and mean Cu intakes (April M + F = 2.2 + 0.4 mg/day; July M + F = 3.0 + 0.6 mg/day) were within the range noted for persons consuming predominantly plant-based diets.

Adult↗
PubMed1986

Significance of perfusion studies in the detection of transient myocardial ischemia.

In summary, myocardial thallium-201 imaging appears to be superior to exercise electrocardiography alone for detection of myocardial ischemia in patients with underlying coronary artery disease and chest pain. Risk stratification and prognostication can also be undertaken utilizing symptom limited stress scintigraphy in patients with stable chest pain syndromes or in conjunction with submaximal exercise thallium-201 scintigraphy after uncomplicated myocardial infarction. Patients with normal perfusion patterns or a single persistent defect have less likelihood of experiencing a subsequent cardiac event compared with patients with high risk scans demonstrating multiple defects in more than one vascular region or redistribution, or both. Thallium-201 imaging can be undertaken in the resting state in patients with unstable angina to detect "resting ischemia" or reversible vasospasm. Finally, the limitations of exercise or rest thallium-201 scintigraphy are discussed.

Angina Pectoris↗