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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 523 records · Page 29Linked to original sources
PubMed1985

Prediction of functional capacity and use of exercise testing for predicting risk after acute myocardial infarction.

This study evaluated whether an ischemic exercise test response or functional capacity could be predicted from data available during hospitalization in patients discharged after acute myocardial infarction (AMI). The value of exercise test variables for predicting death and new AMI within 1 year was also examined. Among 1,469 patients, 466 (32%) underwent treadmill exercise testing around the time of discharge. An ischemic exercise test response (ST-segment depression or angina) could not be predicted. Good functional capacity (more than 4 METs) could be predicted from age and ST-segment changes at rest. Among the 60% of the patients who were predicted to have functional capacity of more than 4 METs, only 15% had poor functional capacity at the time of testing. Multivariate analysis for predicting death and new infarction selected only functional capacity (continuous variable in METs), which classified 72% of the patients into a low-risk group with less than a 2% rate of death and new AMI in the first year. The high-risk group (29% of the patients) had an 18% rate of death or new AMI. It is concluded that functional capacity is the most important exercise test variable and that patients likely to have good functional capacity can be identified on the basis of age and ST-segment changes at rest. Further, the level of functional capacity on exercise testing can identify groups of patients with very low and relatively high risk of death or new AMI within 1 year.

Adrenergic beta-Antagonists↗
PubMed1985

The campomelic syndrome--prenatal ultrasound investigations. A case report.

The campomelic syndrome is a skeletal dysplasia of unknown aetiology which is apparent at birth and is characterized by bilateral bowing of the tibiae, clubfoot and other multiple congenital abnormalities. Up to 50% of cases are either stillborn or die within 24 hours of birth in respiratory distress. With a few exceptions, the remainder die within 10 months. The patient in this report demonstrated characteristic features of the syndrome which were detected antenatally by ultrasound and confirmed after delivery. The apparently female infant died 2 hours postpartum in respiratory distress, but was subsequently found to have a 46,XY chromosome constitution. Autopsy and postmortem radiographs revealed multiple congenital abnormalities consistent with the campomelic syndrome. The findings in this case are discussed and the possibility of antenatal diagnosis is raised.

Cephalometry↗
PubMed1985

Ultrasound examination before amniocentesis and success of culture in genetic referrals. Six years' experience in Cape Town.

Our experience in Cape Town shows that ultrasound examination is of great benefit when amniocentesis is performed to obtain amniotic fluid cells for metaphase plates from patients at risk of carrying a fetus with a genetic disorder. Data taken over a period of 6 years show that the number of blood-contaminated fluid specimens decreases significantly when patients are scanned before amniocentesis is performed. The presence of blood in the fluid increases the possibility that cells will not grow in culture. There was no evidence to suggest that ultrasound examination inhibited amniotic fluid cell growth in culture.

Amniocentesis↗
PubMed1985

Smoking status at the time of acute myocardial infarction and subsequent prognosis.

A population of 2955 patients admitted to the hospital with acute myocardial infarction (AMI) was followed for 1 year after AMI or until death. Smokers as compared to nonsmokers were over 10 years younger (p less than 0.001) and had a lower prevalence of hypertension (p less than 0.01), congestive heart failure (p less than 0.0001), angina pectoris (p less than 0.01), and diabetes (p less than 0.0001). They had less severe myocardial infarction evidenced, for example, by lower prevalence of pulmonary congestion on chest x-ray (p less than 0.01). Both early (1 month) and late (6 and 12 months) mortality rates were lower in the smoking population (p less than 0.0001 at 1 month, p less than 0.05 at 6 months, and p less than 0.01 at 1 year). Adjusting for age and other variables reduced but did not reverse the survival differential favoring smokers at 1 month, but adjusting for age alone eliminated the differences in mortality rates at 6 and 12 months. We conclude that while smoking is a risk factor for cardiovascular disease and may contribute to the occurrence of AMI at a younger age, smoking at the time of AMI does not appear to be an independent predictor of death during the first year after AMI.

Age Factors↗
PubMed1985

Quantitation of regional left ventricular function by two-dimensional echocardiography in normals and patients with coronary artery disease.

Regional endocardial motion and wall thickening of the left ventricle were quantitatively assessed in nine normal subjects and in 21 patients with coronary artery disease using two-dimensional echocardiography (2DE) and a computerized light pen system. Eight equal sectors of a cross-sectional image from parasternal short-axis, apical four-and two-chamber views were used for measuring sector area difference of endocardial motion and wall thickness between end diastole and end systole. In 13 patients with anterior wall motion abnormalities, area difference of wall thickening found by 2DE was abnormal in 12 of 13 (92%) patients, and only in 6 of 13 (46%) patients by endocardial motion. In 10 patients with dyskinetic regions in apex or anterior wall, dyskinesia by wall thickening was found in all patients, but only in 6 of 10 (60%) by endocardial motion. Thus, wall thickening assessed by 2DE is a more sensitive technique than analysis of endocardial motion in evaluating regional wall motion abnormalities in patients with coronary artery disease.

Adolescent↗
PubMed1985

Flail mitral valve syndrome: comparison with chronic mitral regurgitation of other etiologies.

Thirty-nine patients with symptomatic severe mitral regurgitation (MR) were studied by cardiac catheterization and two-dimensional echocardiography (2DE) prior to mitral valve replacement. A flail mitral valve was found at surgery in 23 patients (group 1); 16 patients had intact chordae tendineae (chronic MR, group 2). No difference was found between groups 1 and 2 with regard to hemodynamic findings. Left atrial volumes in end systole (LAESV) and end diastole (LAEDV) were determined by 2DE from apical four- and two-chamber views with the use of a biplane area-length method and a light pen system. The LAESV and LAEDV measured 116 +/- 66 ml and 56 +/- 48 ml, respectively, in group 1, as compared with 185 +/- 101 ml and 105 +/- 62 ml in group 2 (p less than 0.025). Ten patients from group 1 with LAESV less than or equal to 100 ml (group 1A) were compared to the remaining 13 patients with LAESV greater than 100 ml (group 1B). Patients in group 1A had significantly smaller left ventricular volume and higher mean pulmonary wedge pressure, pulmonary artery, and left ventricular end-diastolic pressure compared to patients in groups 1B and 2 (p less than 0.05). Thus, a subset group of patients with flail mitral leaflets and smaller LAESV has hemodynamic features of acute MR, whereas the remainder with larger LAESV are indistinguishable from patients with chronic MR.

Adult↗
PubMed1985

Effect of coronary bypass surgery and valve replacement on left ventricular function: assessment by intraoperative two-dimensional echocardiography.

Intraoperative two-dimensional echocardiography (2DE) was performed in 15 patients during coronary artery bypass grafting (CABG) and in 14 patients during aortic (AVR) or mitral valve replacement (MVR) before and immediately after cardiopulmonary bypass by means of a 3.5 MHz transducer. Left ventricular ejection fraction (LVEF), end-diastolic (LVEDV) and end-systolic (LVESV) volumes were measured by a light pen system and biplane Simpson's rule from short-axis and apical two-chamber views. In seven patients with CABG and new abnormal Q waves or greater than 5% MB to total CPK ratio postoperatively, the mean LVEF decreased significantly (from 52 +/- 10 to 43 +/- 12%, p = 0.005). Patients undergoing MVR for mitral regurgitation showed, a significant decrease in LVEF (from 63 +/- 10 to 42 +/- 23%, p less than 0.025) and LVEDV (from 166 +/- 34 to 147 +/- 44 ml, p less than 0.05). Mean LVEF also decreased after AVR for aortic regurgitation (from 46 +/- 16 to 26 +/- 15%, p less than 0.05). Six patients with valve replacement and postoperative hypotension had the greatest decrease in intraoperative LVEF (from 50 +/- 12 to 24 +/- 10%, p less than 0.005). It is concluded that: Intraoperative 2DE can be used to assess immediate changes in left ventricular function after CABG or valve replacement. LVEF decreases significantly immediately after AVR for aortic regurgitation and MVR for mitral regurgitation. Intraoperative 2DE may identify those patients who can benefit from inotropic support in the immediate postoperative period after valve replacement.

Adult↗
PubMed1985

Differentiation of apurinic/apyrimidinic sites and single-strand breaks in DNA by formamide- and alkaline-sucrose gradient sedimentation.

The excision repair of DNA damaged by physical or chemical agents may produce either apurinic/apyrimidinic (AP) sites or single-strand breaks (SSB) in the DNA. Alkaline-sucrose gradient sedimentation and alkaline elution, techniques generally used for the study of DNA repair which depend upon high pH to denature the DNA, cannot differentiate between these possibilities. A simple method for the quantitative measurement of SSB in DNA which leaves any AP sites intact is presented. This method relies upon the separation by size of the fragments resulting from the denaturation of the DNA under neutral conditions by sedimentation through gradients of sucrose in formamide. By combining the use of both formamide- and alkaline-sucrose sedimentation methods, we can quantify both AP sites and SSB in DNA.

Apurinic Acid↗
PubMed1985

Local regulation of luminance gain.

Contrast sensitivity was measured for sinusoidal gratings sampled by compressing luminance into a variable number of sample bars. This procedure does not affect the amplitude or mean luminance of the grating, but does increase the local luminance of the sample bars: the fewer the bars, the more luminous they are. It was found that sensitivity increased with bars per cycle, particularly at low spatial frequencies. Further experiments, in which the local luminance of the sampling bars (but not the average luminance of the grating) was varied by addition of veiling glare showed that contrast sensitivity varied inversely with local bar luminance (a Weber type relationship). We interpret the results as evidence of local gain control under conditions where average luminance, and hence mean photon flux, does not vary. Calculations based on variation of sensitivity with spatial frequency suggest that gain control can be very localized, with receptive fields of Gaussian space constant of 0.5' arc. The relevance of these results to modern psychophysical concepts, including the definition of contrast is discussed.

Form Perception↗
PubMed1985

Cardiac function in patients with cystic fibrosis: evaluation by two-dimensional and Doppler echocardiography.

Two-dimensional and Doppler echocardiography were performed in 17 consecutive hospitalized patients with cystic fibrosis aged 6 to 38 years (mean 21 +/- 9) and in 10 normal subjects aged 24 +/- 7 years. Left ventricular and right ventricular ejection fraction were measured by a computerized light pen system and Simpson's rule from two-dimensional echocardiographic apical four and two chamber views. Right ventricular wall thickness, inferior vena cava size and the presence of tricuspid regurgitation by Doppler recording were also assessed. National Institutes of Health (NIH) score of clinical severity ranged from 22 to 72 (mean 51 +/- 15) (100 = excellent, 0 = poor). Four patients, all with an NIH score of 40 or less, died of respiratory failure within 1 year of the echocardiographic study. There was no significant difference between patients with cystic fibrosis and normal subjects with regard to right ventricular ejection fraction (59 +/- 11 versus 61 +/- 10%), left ventricular ejection fraction (67 +/- 8 versus 70 +/- 8%) and right ventricular systolic (5 +/- 1 versus 5 +/- 0.5 mm) and diastolic (2.4 +/- 0.5 versus 2.5 +/- 0.5 mm) wall thicknesses. A dilated inferior vena cava and mild tricuspid regurgitation by Doppler recording were detected in only one patient. A poor correlation was found between right ventricular ejection fraction and NIH clinical score (r = 0.26), chest X-ray score (r = 0.29) and pulmonary function tests. It is concluded that right and left ventricular systolic function is preserved in patients with moderately severe cystic fibrosis; clinical status in these patients is probably determined by the pulmonary rather than cardiac involvement.

Adolescent↗
PubMed1985

Afterload mismatch in aortic and mitral valve disease: implications for surgical therapy.

In the management of patients with valvular heart disease, an understanding of the effects of altered loading conditions on the left ventricle is important in reaching a proper decision concerning the timing of corrective operation. In acquired valvular aortic stenosis, concentric hypertrophy generally maintains left ventricular chamber size and ejection fraction within normal limits, but in late stage disease function can deteriorate as preload reserve is lost and aortic stenosis progresses. In this setting, even when the ejection fraction is markedly reduced (less than 25%), it can improve to normal after aortic valve replacement, suggesting that afterload mismatch rather than irreversibly depressed myocardial contractility was responsible for left ventricular failure. Therefore, patients with severe aortic stenosis and symptoms should not be denied operation because of impaired cardiac function. In chronic severe aortic and mitral regurgitation, operation is generally recommended when symptoms are present, but whether to recommend operation to prevent irreversible myocardial damage in patients with few or no symptoms has remained controversial. In aortic regurgitation, left ventricular function generally improves postoperatively, even if it is moderately impaired preoperatively, indicating correction of afterload mismatch. Most such patients can be carefully followed by echocardiography. However, in some patients, severe left ventricular dysfunction fails to improve postoperatively. Therefore, when echocardiographic studies in the patient with severe aortic regurgitation show an ejection fraction of less than 40% (fractional shortening less than 25%) plus enlarging left ventricular end-diastolic diameter (approaching 38 mm/m2 body surface area) and end-systolic diameter (approaching 50 mm or 26 mm/m2), confirmation of these findings by cardiac catheterization and consideration of operation are advisable even in patients with minimal symptoms. In chronic mitral regurgitation, maintenance of a normal ejection fraction can mask depressed myocardial contractility. Pre- and postoperative studies in such patients have shown a poor clinical result after mitral valve replacement, associated with a sharp decrease in the ejection fraction after operation. This response appears to reflect unmasking of decreased myocardial contractility by mitral valve replacement, with ejection of the total stroke volume into the high impedance of the aorta (afterload mismatch produced by operation).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Extracardiac and coronary vascular effects of digitalis.

The administration of digitalis glycosides causes a variety of extracardiac effects. In both normal human subjects and in other species, digitalis increases smooth muscle tone of resistance and capacitance vessels. The vasoconstriction is mediated, in part, by a direct action of these glycosides on smooth muscle and, in part, by an increase in alpha-adrenergic tone. Constriction of coronary and splanchnic vessels may lead to myocardial or mesenteric ischemia. In contrast to normal subjects, patients with congestive heart failure demonstrate arteriolar and venodilation in response to these glycosides, possibly because the myocardial effect, to increase cardiac output and peripheral blood flow, overcomes the vasoconstrictor properties of these drugs. Other important actions of digitalis glycosides occur in the central and peripheral nervous systems. Their effects on the area postrema of the medulla oblongata are largely responsible for the alpha-adrenergic-mediated peripheral vasoconstriction, as well as the nausea and vomiting that frequently accompany digitalis intoxication. Actions of glycosides on the cerebral cortex are responsible for the wide range of neurotoxic effects that range from visual disturbances and headaches to seizures and coma. Finally, peripheral neurologic effects of digitalis glycosides on baroreceptor and cardiac afferent fibers may: improve the depressed function of these receptors in the situation of heart failure, and reflexly lower peripheral vascular resistance, thereby partially preventing the vascular constrictor action of these glycosides.

Animals↗
PubMed1985

Survival after hospital discharge in matched populations with inferior or anterior myocardial infarction.

Prognostic differences between patients with anterior or inferior myocardial infarction are often related to such variables as previous infarction or the size of the myocardial infarct. We examined the determinants of mortality in 997 hospital survivors of acute Q wave infarction (anterior in 449, inferior in 548) who, although not preselected, were well matched with respect to age, sex and prior infarction or congestive heart failure. Additionally, there was no significant difference in peak serum creatine kinase (CK) between the groups with anterior and inferior infarction (1,459 +/- 1,004 versus 1,357 +/- 1,036). Among the patients with anterior infarction who died during the 1 year follow-up period, 56% died in the first 60 days after hospital discharge compared with 18% of those without inferior infarction (p less than 0.01). Survival curves then became nearly identical at 3 months, and remained so until 1 year when the total mortality rate was 10% for the anterior and 7% for the inferior infarction group (p = NS). Variables associated with heart failure during the hospital phase were more prevalent in anterior infarction, but rales above the scapulae during the hospital stay (p less than 0.0001) and ventricular gallop at the time of discharge (p less than 0.0001) were the top two predictors of 1 year mortality by both univariate and multivariate analysis in inferior infarction. Age (p less than 0.0001) and peripheral edema (p less than 0.0001) were the strongest predictors of mortality in anterior infarction. Previous infarction, although just as common in the group with anterior infarction, was present at 1 year in 48% of nonsurvivors of the group with inferior infarction compared with only 19% of survivors (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Nonuniformity of inner and outer systolic wall thickening in conscious dogs.

Transmural differences in systolic wall thickening were analyzed in 13 conscious dogs by implanting sonomicrometers to continuously measure total wall thickness (WT) and outer WT approximately half the distance through the myocardium at a closely adjacent location. Inner WT was derived by subtraction of outer WT from total WT. Outer wall measurements spanned, on average, the outer 44 +/- 10% (+/- SD) of the wall; derived inner wall measurements spanned the remaining 56 +/- 10%. At rest the fractional contribution (FC) of the outer wall to total systolic wall thickening was 29 +/- 9%, which was significantly less than the FC of the inner wall, 71 +/- 9%. These data are in good agreement with simplified modeling of a cross section of the left ventricle as two concentric rings that predicts that the FC of inner and outer halves of the wall should be approximately 67 and 33%, respectively. During treadmill exercise, the extent of both inner and outer thickening increased significantly (30 and 29%, respectively) but the relative FC of the inner and outer wall remained the same. The data indicate that systolic wall thickening is nonuniform and that this nonuniformity remains constant during the increased inotropic and chronotropic stimulation associated with exercise.

Animals↗
PubMed1985

Prognosis after extension of myocardial infarct: the role of Q wave or non-Q wave infarction.

We examined whether or not subsets of patients with extension of myocardial infarct were at high risk for early and late mortality. Some data suggest increased risk in patients with non-Q wave infarcts and we hypothesized that infarct extension in this group might be associated with a poorer prognosis than that for patients with extension of Q wave infarcts. A total of 1253 patients with acute myocardial infarction who were included in our data base were followed prospectively. The patients were classified according to electrocardiographic results into the following groups: those with non-Q wave (n = 277) infarcts and those with Q-anterior (n = 462) and Q-inferior (n = 497) infarcts. Extension was diagnosed by two of the following criteria: (1) recurrent chest pain 24 hr or more after admission to the hospital, (2) new persistent electrocardiographic changes, and (3) elevation or reappearance of creatine kinase. By these criteria 85 (6%) patients had extension (8% of non-Q wave infarcts, 6% of Q-anterior infarcts, and 6% of Q-inferior infarcts). Hospital mortality in patients with extension was 15% in those with Q wave infarcts vs 43% in those with non-Q wave infarcts (p less than .01). Nine hundred and fifty-two patients were followed for 1 year. In 24% of those who did not survive 1 year there was extension of infarct; only 6% of survivors had extension (p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1985

Effect of the combination of diltiazem and atenolol on exercise-induced regional myocardial ischemia in conscious dogs.

The effect of combination therapy with diltiazem and atenolol on the regional myocardial blood flow-function relationship was studied in eight conscious dogs with chronic coronary artery stenosis. An ameroid constrictor and hydraulic occluder were placed around the left circumflex coronary artery, sonomicrometers were implanted for measuring wall thickness in control and ischemic regions, and regional myocardial blood flow was measured with the microsphere method. Eighteen days (average) after surgery, resting regional myocardial function and blood flow were normal, but treadmill exercise induced severe regional myocardial dysfunction in the posterior wall (wall thickening during systole reduced from 25.5% to 2.7%, a 90% reduction). Subendocardial blood flow decreased by 68% from the control standing value, while subepicardial flow increased. An identical exercise bout was performed 3 hr after administration of atenolol (1.0 mg/kg orally) and 15 min after administration of diltiazem (0.3 mg/kg iv). Heart rate during running was significantly lower as were left ventricular peak systolic pressure, end-diastolic pressure, and peak dP/dt. Wall thickening in the control region was not augmented during exercise after atenolol and diltiazem. There was less dysfunction in the ischemic region (35% reduction) and the improved performance was accompanied by a substantial increase in subendocardial perfusion (0.31 +/- 0.14 vs 0.61 +/- 0.30 ml/min/g, a 36% reduction from rest). Epicardial flow was unchanged, and the endocardial/epicardial ratio increased (0.27 +/- 0.13 vs 0.62 +/- 0.29). Recovery time for regional wall thickening also improved. The beneficial effects of the combination of atenolol and diltiazem in a preparation of single-vessel chronic coronary stenosis were shown to be significantly greater than those of either drug alone.

Animals↗