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Biomedical subjects

R D Abbott

Publications and source records attributed to R D Abbott.

At least 19 recordsLinked to original sources
PubMed1992

Effect of increased neck vein pressure on intestinal lymphatic pressure in awake sheep.

Lymphatic vessels from the intestines drain into the thoracic duct, and the thoracic duct empties into veins in the neck. Thus increases in neck vein pressure (PNV) might slow intestinal lymph flow, provided the increased pressure is reflected upstream through the lymphatic vessels. To test the effect of increases in PNV on lymphatic pressure, we cannulated intestinal lymphatics in the direction of flow in six sheep. After the sheep recovered from surgery, we measured the pressure in the lymphatics (Px) as we increased PNV in steps. Px increased only slightly (but significantly) from 7.4 +/- 2.0 to 11.4 +/- 5.2 (SD) cmH2O when we increased PNV from baseline (0.8 +/- 2.4 cmH2O) to 37.4 +/- 4.1 cmH2O. However, when we simulated an increased lymph flow by infusing Ringer solution into the lymphatics at 1,000 microliters/min, Px increased to 24.6 +/- 7.0 cmH2O at PNV equal to 37.1 +/- 5.3 cmH2O. These results indicate that, at normal lymph flow rates, increases in neck vein pressure cause only small increases in intestinal lymphatic pressure. On the other hand, when lymph flow is elevated, increases in neck vein pressure may substantially increase lymphatic pressure and thus slow intestinal lymph flow.

Animals↗
PubMed1992

Independent and incremental prognostic value of tests performed in hierarchical order to evaluate patients with suspected coronary artery disease. Validation of models based on these tests.

BACKGROUND: The additive prognostic value of tests done in a hierarchical order for the detection of coronary artery disease (CAD) is not always known. The principal goal of this study, therefore, was to assess the incremental prognostic value of data obtained in succession (clinical, exercise stress testing, 201Tl imaging, and coronary angiography) in patients with suspected CAD. A second goal was to develop models for determining prognosis based on results of these tests and to test the clinical validity of these models in unrelated patients. METHODS AND RESULTS: Data from two groups of patients who had undergone such evaluation and had been followed for a mean of 4.4 years were analyzed. There were 204 patients from Massachusetts General Hospital (MGH) and 299 from the University of Virginia (UVA). There were 20 deaths and 21 nonfatal infarctions in the MGH group and 41 deaths and nine infarctions in the UVA group. Both univariate and multivariate Cox regression analyses were performed to assess the individual and incremental prognostic value of these tests. In both groups, 201Tl imaging provided significant additional prognostic information compared with clinical and exercise stress test data (p less than 0.05). At MGH, where the lung/heart 201Tl ratio had been analyzed, coronary angiography did not provide additional prognostic information. In this group of patients, the combination of clinical and exercise 201Tl variables provided greater prognostic information than the combination of clinical and angiographic data (p less than 0.001). In the UVA cohort, in which the lung/heart ratio had not been analyzed, coronary angiography provided incremental prognostic information compared with clinical and exercise 201Tl data alone (p less than 0.05). When models developed using data from either sample were applied to the other unrelated sample, there was often close agreement between the overall observed rates and those predicted by the models. This was also true for the low-risk and high-risk subgroups. Some models, however, did not perform as well as other models, which suggests that models that do well in one sample may not always be generalized to other groups. CONCLUSIONS: Tests performed in hierarchical order for the evaluation of suspected CAD provide additional prognostic information. Models developed using clinically relevant combinations of test results obtained from different patient populations are frequently able to predict absolute levels of survival in unrelated but similar samples.

Cohort Studies↗
PubMed1991

Prediction of outcome after mitral valve replacement in patients with symptomatic chronic mitral regurgitation. The importance of left atrial size.

BACKGROUND: The ability to predict outcome after mitral valve replacement remains limited in patients with symptomatic chronic mitral regurgitation. The aims of this study were to determine the preoperative predictors of postoperative cardiac-related mortality and to assess the additive prognostic value of tests performed in such patients. METHODS AND RESULTS: Accordingly, 176 patients (mean age, 57 +/- 14 years) who underwent mitral valve replacement were followed up for 3.8 +/- 0.5 years. Four categories of variables were analyzed to predict postoperative cardiac-related mortality: clinical, laboratory, two-dimensional echocardiographic (2DE), and cardiac catheterization. There were 39 cardiac-related deaths (29 due to congestive heart failure and 10 sudden). When the four categories were analyzed separately, two clinical, one laboratory, two 2DE, and one catheterization variable best predicted postoperative death. When these six variables were examined simultaneously, only three (one clinical and two 2DE) remained significant predictors of cardiac-related mortality: presence of pulmonary rales, left atrial size, and the ratio of left ventricular wall thickness to left ventricular cavity dimension in end systole. A model based on these three variables may predict cardiac-related death with considerable accuracy. Laboratory data did not add to clinical information for predicting death. 2DE variables provided significant additional information in this regard (p less than 0.001). Further addition of catheterization variables was not useful. Prognostic value did not change significantly when 50 patients with prior mitral valve surgery or 49 patients undergoing concomitant aortic valve replacement or coronary artery bypass surgery were excluded from analysis. CONCLUSIONS: We conclude that 1) measures of both left ventricular systolic function and left atrial size are equally important in predicting postoperative cardiac-related mortality in patients with symptomatic chronic mitral regurgitation undergoing mitral valve replacement; 2) left atrial size may be important because it reflects the "history" (severity and duration) of mitral regurgitation; 3) 2DE assessment of left atrial size and left ventricular function provides prognostic information that is significantly greater than that obtained from clinical and laboratory parameters alone; the addition of catheterization variables does not increase the prognostic value of the clinical and 2DE data.

Atrial Function, Left↗
PubMed1991

Importance of two-dimensional echocardiographic assessment of left ventricular systolic function in patients presenting to the emergency room with cardiac-related symptoms.

BACKGROUND: This prospective study was designed to test the hypothesis that the assessment of left ventricular systolic function at the time of emergency room (ER) presentation provides valuable diagnostic and prognostic information in patients with cardiac-related symptoms. METHODS AND RESULTS: The study is based on a 2-year follow-up of 171 consecutive patients evaluated in the ER for such symptoms. In the course of follow-up, one third of the patients (55 of 171) suffered a major cardiac event. For those with left ventricular systolic dysfunction (LVSD), the age-adjusted rate of early events (occurring within 48 hours of presentation) was more than eight times higher than for those without LVSD (26.9% versus 3.3%, p less than 0.01). For events occurring after 48 hours of ER presentation, LVSD was associated with a nearly fourfold excess of cardiac events (23.9% versus 6.4%, p less than 0.01). Other than advanced age, the most important confounder for early events included an abnormal electrocardiogram diagnostic for acute myocardial infarction. Confounders for late events included advanced age and a history of hypertension. LVSD on two-dimensional echocardiography (2DE) was the only finding associated with early and late events after controlling for other risk factors. In addition, the prediction of these events derived from the combination of historical, clinical, electrocardiographic, and 2DE findings was significantly improved when accounting for the presence or absence of LVSD (p less than 0.01). CONCLUSIONS: We conclude that the 2DE assessment of left ventricular systolic function provides valuable diagnostic and prognostic information in subjects presenting to the ER with cardiac-related symptoms.

Angina Pectoris↗
PubMed1991

Atrial fibrillation as an independent risk factor for stroke: the Framingham Study.

The impact of nonrheumatic atrial fibrillation, hypertension, coronary heart disease, and cardiac failure on stroke incidence was examined in 5,070 participants in the Framingham Study after 34 years of follow-up. Compared with subjects free of these conditions, the age-adjusted incidence of stroke was more than doubled in the presence of coronary heart disease (p less than 0.001) and more than trebled in the presence of hypertension (p less than 0.001). There was a more than fourfold excess of stroke in subjects with cardiac failure (p less than 0.001) and a near fivefold excess when atrial fibrillation was present (p less than 0.001). In persons with coronary heart disease or cardiac failure, atrial fibrillation doubled the stroke risk in men and trebled the risk in women. With increasing age the effects of hypertension, coronary heart disease, and cardiac failure on the risk of stroke became progressively weaker (p less than 0.05). Advancing age, however, did not reduce the significant impact of atrial fibrillation. For persons aged 80-89 years, atrial fibrillation was the sole cardiovascular condition to exert an independent effect on stroke incidence (p less than 0.001). The attributable risk of stroke for all cardiovascular contributors decreased with age except for atrial fibrillation, for which the attributable risk increased significantly (p less than 0.01), rising from 1.5% for those aged 50-59 years to 23.5% for those aged 80-89 years. While these findings highlight the impact of each cardiovascular condition on the risk of stroke, the data suggest that the elderly are particularly vulnerable to stroke when atrial fibrillation is present.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

A model to predict multivessel coronary artery disease from the exercise thallium-201 stress test.

PURPOSE: The aim of this study was to (1) determine whether nonimaging variables add to the diagnostic information available from exercise thallium-201 images for the detection of multivessel coronary artery disease; and (2) to develop a model based on the exercise thallium-201 stress test to predict the presence of multivessel disease. PATIENTS AND METHODS: The study populations included 383 patients referred to the University of Virginia and 325 patients referred to the Massachusetts General Hospital for evaluation of chest pain. All patients underwent both cardiac catheterization and exercise thallium-201 stress testing between 1978 and 1981. RESULTS: In the University of Virginia cohort, at each level of thallium-201 abnormality (no defects, one defect, more than one defect), ST depression and patient age added significantly in the detection of multivessel disease. Logistic regression analysis using data from these patients identified three independent predictors of multivessel disease: initial thallium-201 defects, ST depression, and age. A model was developed to predict multivessel disease based on these variables. As might be expected, the risk of multivessel disease predicted by the model was similar to that actually observed in the University of Virginia population. More importantly, however, the model was accurate in predicting the occurrence of multivessel disease in the unrelated population studied at the Massachusetts General Hospital. CONCLUSION: It is, therefore, concluded that (1) nonimaging variables (age and exercise-induced ST depression) add independent information to thallium-201 imaging data in the detection of multivessel disease; and (2) a model has been developed based on the exercise thallium-201 stress test that can accurately predict the probability of multivessel disease in other populations.

Arrhythmias, Cardiac↗
PubMed1990

Epidemiology of some peripheral arterial findings in diabetic men and women: experiences from the Framingham Study.

PURPOSE AND PATIENTS AND METHODS: The purpose of this study was to determine the relationship between diabetes and the development of some peripheral arterial findings--carotid and femoral bruits and nonpalpable pedal pulse--and acute cardiovascular events in 1,196 men and 1,582 women based on 20-year follow-up data in the Framingham Study. RESULTS: For both men and women without diabetes, the incidence of carotid bruits and nonpalapble pedal pulses increased significantly with age (p less than 0.05) without any apparent male predominance. In contrast, diabetic men and women were at an elevated risk of each peripheral arterial condition that was not appreciably different across age groups. Compared with women without diabetes, those with diabetes experienced nearly a twofold excess of femoral bruits (p less than 0.05) and a 50% excess of nonpalpable pedal pulses (p less than 0.01). Among men, diabetes nearly doubled the risk of carotid bruits (p less than 0.05). Those who had both diabetes and symptoms of peripheral arterial disease were at especially high risk of incident cardiovascular events. In particular, nonpalpable pedal pulses were associated with more than a twofold excess of coronary heart disease (p less than 0.05) and stroke (p less than 0.01) in diabetic women and more than a twofold excess of coronary heart disease and cardiac failure in diabetic men (p less than 0.01). Femoral bruits doubled the risk of coronary heart disease in diabetic men (p less than 0.05). CONCLUSION: We conclude that while diabetes predisposes to various forms and locations of peripheral arterial disease, the enhanced risk of acute cardiovascular events experienced by diabetic patients is increased further when diabetes is accompanied by indications of a peripheral arterial condition. Since signs of peripheral arterial disease may suggest an impending or coexistent atherosclerotic process, careful examination of arterial circulation by evaluating peripheral pulses and assessing whether bruits are present is important.

Cerebrovascular Disorders↗
PubMed1990

Longitudinally measured blood pressure, antihypertensive medication use, and cognitive performance: the Framingham Study.

The relation of longitudinally measured blood pressure to cognitive performance in the absence of clinically diagnosed cerebrovascular disease was investigated in the Framingham Study. In 1976-1978, neuropsychologic testing was administered to 1993 participants aged 55-89 years. Performance on an education-adjusted composite of these tests was examined in relation to measures of chronicity of hypertension as well as the average systolic and average diastolic blood pressure. All analyses were stratified by antihypertensive medication use during the 2 years prior to cognitive testing and adjusted for age, sex, occupation, alcohol consumption, and participation rate in prior examination cycles. Among subjects on drug therapy for hypertension, there was no association between cognitive performance and longitudinally measured blood pressure. The proportion of cycles in which hypertension was present and average systolic and diastolic blood pressure had a significant inverse relation with cognitive performance only in the group not on antihypertensive drug therapy. However, among subjects on antihypertensive medication at earlier cycles, there was a highly significant graded relation between cognitive impairment and the probability of being off medication at the time of testing. These results suggest that hypertension-related subclinical vascular disease is not an important cause of cognitive impairment in the elderly. Cognitive impairment may, however, be associated with a reduced adherence to drug treatment regimens.

Aged↗
PubMed1990

Effect of diuretic use on the development of diabetes mellitus. The Framingham study.

The hypothesis that diuretic use may increase the risk of diabetes mellitus was prospectively examined in men and women aged 50 years and over in the Framingham study. Age-adjusted relative risk estimates were calculated comparing the rate of diabetes among those who took diuretics to those who did not take these medications. The relative risks (95% confidence limits) were statistically elevated (P less than 0.05) in both sexes; 2.1 (1.2, 3.6) in men and 2.5 (1.4, 4.5) in women. After covariate adjustment for body mass index, concentrations of total cholesterol, high density lipoprotein cholesterol, very low density cholesterol, systolic blood pressure, and cigarette smoking the relative risks were no longer statistically significant; 1.2 (0.6, 2.4) for men and 1.6 (0.8, 3.2) for women. These results are suggestive of a possible deleterious affect of diuretic use particularly in women and indicate that persons receiving diuretic agents should be carefully monitored for adverse changes in other risk factors.

Diabetes Mellitus↗
PubMed1989

Frequency of uncomplicated angina pectoris in type A compared with type B persons (the Framingham Study).

The impact of type A behavior on coronary artery disease was examined in 570 men and 719 women based on 20 years of follow-up in the Framingham Study. A comparison of type A and B persons showed similar levels of systolic blood pressure, total and high density lipoprotein cholesterol and body mass index. Behavioral status also was unrelated to diabetes, cigarette smoking and alcohol intake. Despite similar cardiovascular risk profiles, type A behavior was associated with more than a 2-fold excess risk of angina pectoris, uncomplicated by other symptoms of coronary artery disease (p less than 0.05 for men and p less than 0.01 for women). Type A behavior, however, was not related to an increased risk of myocardial infarction and fatal coronary events. Among the victims of uncomplicated angina, the risk of subsequent coronary morbidity and mortality in both type A and type B men and women increased by more than 4-fold (p less than 0.001). Although the risk was reduced among type A persons, it was not statistically significant. It is concluded that uncomplicated angina pectoris occurs with greater frequency in type A persons than in those who are type B, without explanation by concomitant risk factors. In addition, the prognosis for myocardial infarction and coronary artery disease mortality in angina patients classified as type A is as serious as the prognosis for those who are type B.

Angina Pectoris↗
PubMed1989

Cardiovascular risk factors and graded treadmill exercise endurance in healthy adults: The Framingham Offspring Study.

To help describe the association between exercise endurance and cardiovascular risk factor profiles, 2,606 young and middle-aged healthy adults in the Framingham Offspring Study were given submaximal treadmill tests. For both men and women, exercise endurance was inversely related to resting heart rate (p less than 0.001), body mass index (p less than 0.001), systolic blood pressure (p less than 0.001) and blood glucose (p less than 0.01), and positively related to high density lipoprotein (HDL) cholesterol (p less than 0.05). In men, cigarette smoking (p less than 0.05), high levels of total cholesterol (p less than 0.01) and very low density lipoprotein (VLDL) cholesterol (p less than 0.001) were also associated with poor exercise endurance. After adjusting for age, resting heart rate and body mass index, significant independent associations persisted for HDL cholesterol (p less than 0.05) in both sexes and for systolic blood pressure, VLDL cholesterol, blood glucose and cigarette smoking in men (p less than 0.05). Risk factors associated with overt cardiovascular disease in older individuals are also associated with poor exercise endurance in those who are younger and asymptomatic.

Adolescent↗
PubMed1989

Changes in hypertension treatment and in congestive heart failure mortality in the United States.

The use of antihypertensive agents has increased in recent years and has been more marked among individuals in older age groups (65-74 years) than in middle-aged groups (45-54 years). Because hypertension is a strong risk factor for the development of congestive heart failure, more common use of antihypertensive agents would be expected to reduce the incidence of congestive heart failure. Examination of the national death statistics reveals decreases in congestive heart failure mortality at younger ages with mortality increases at older ages. The reasons for these divergent trends in congestive heart failure mortality in different ages and the apparent inconsistency with respect to the changes in the use of antihypertensive drugs are explored. We speculate that antihypertensive treatment does not completely prevent congestive heart failure but merely postpones its development by several decades.

Adult↗
PubMed1989

Diabetes, intermittent claudication, and risk of cardiovascular events. The Framingham Study.

The impact of diabetes on intermittent claudication was examined in 1813 men and 2504 women with 34-yr follow-up data in the Framingham study. For both sexes, diabetes was associated with a two- to threefold excess risk of intermittent claudication compared with its absence. A pronounced excess risk was also observed in subjects on oral hypoglycemic therapy and in women receiving insulin. Although diabetes was often associated with an atherogenic-risk profile, controlling for age and several concomitant risk factors failed to eliminate the association with intermittent claudication. Those who developed both intermittent claudication and diabetes were at an especially high risk of incident cardiovascular events. In women, the risk of coronary heart disease, stroke, and cardiac failure was increased 3-4 times when diabetes and intermittent claudication occurred together compared with when either condition existed alone. In diabetic men, the presence of intermittent claudication doubled the risk of stroke, and cardiac failure was approximately 3 times more likely in subjects with both conditions compared with either alone. We conclude that diabetes is an important risk factor for intermittent claudication, which in turn confers a serious prognosis for subsequent cardiovascular outcomes in the patient with diabetes.

Blood Glucose↗
PubMed1988

The impact of diabetes on survival following myocardial infarction in men vs women. The Framingham Study.

The impact of diabetes on recurrent myocardial infarction (MI) and fatal coronary heart disease was examined in survivors of an initial MI using 34-year follow-up data in the Framingham Study. Among nondiabetic patients, the risk of fatal coronary heart disease was significantly lower in women compared with men (relative risk, 0.6). In the presence of diabetes, however, the risk of recurrent MI in women was twice the risk in men. In addition, the effect of diabetes doubled the risk of recurrent MI in women (relative risk, 2.1) but had an insignificant effect in men. Increased susceptibility to cardiac failure among diabetic women was an important factor in determining survivorship. Women with diabetes developed cardiac failure four times more often (16%) than women without diabetes (3.8%). Furthermore, when cardiac failure developed, 25% of diabetic women experienced a recurrent MI or fatal coronary event, more than doubling the rate when diabetes was absent. We conclude that in the diabetic patient who survives an MI, cardiac failure is a common occurrence, warranting early detection and vigorous management in periods of convalescence and follow-up. In addition, when cardiac failure appears, control of diabetes assumes added importance, particularly in women, where its effect on survivorship is considerable.

Age Factors↗
PubMed1988

Gout and coronary heart disease: the Framingham Study.

The relationship between gout, not associated with the use of diuretics, and the development of coronary heart disease was examined in 5209 subjects originally enrolled in the Framingham Study. Based on 32 years of follow-up, the two year incidence of gout was six times greater in men (3.2/1000) as compared to women (0.5/1000). For both sexes, the incidence of gout showed no clear relationship with age. Among men who never received diuretics, those afflicted by gout, as compared to those without gout, experienced a 60% excess of coronary heart disease (95% confidence limits, 1.1-2.2), primarily attributed to a two fold excess of angina pectoris (95% confidence limits, 1.2-3.1). Although gout was usually associated with other atherogenic risk factors, control of systolic blood pressure, total cholesterol, alcohol intake, body mass index, and diabetes failed to alter the effect of gout on the preceding coronary events in men. For women, there were no significant associations between gout and coronary heart disease. We conclude that gout, unrelated to the intake of diuretics, imparts an additional risk of coronary heart disease in men, unexplained by clinically measured risk factors.

Adult↗
PubMed1988

Physical activity and coronary heart disease in middle-aged and elderly men: the Honolulu Heart Program.

The relationship of physical activity to the development of definite coronary heart disease was examined separately in middle-aged (45-64 years) and elderly men (65-69 years) participating in the Honolulu Heart Program. After 12 years of follow-up, results indicate that increased levels of physical activity reported at study entry were inversely related to the risk of definite coronary heart disease in both age groups. In particular, among those aged 45 to 64 years, the rate of definite coronary heart disease in men who led active life styles was 30 per cent lower than the rate experienced by those who were less active (relative risk, 0.69; 95% confidence interval, 0.53, 0.88). In those older than 64 years, the rate of definite coronary heart disease in active men was less than half the rate experienced by those who led more sedentary life styles (relative risk, 0.43; 95% CI, 0.19, 0.99). These results continued to hold up when controlling for several cardiovascular risk factors and potentially confounding variables, supporting earlier observations that physical activity is beneficial in middle-age, and further suggesting that benefits may extend to the elderly male population as well.

Aged↗
PubMed1988

A test of the multiple connections model of reading acquisition.

Within the framework of Society of Mind Theory (Minsky, 1986), learning to read is conceptualized as a process of creating new communication links or neural connections between an existing visual society and an existing linguistic society. Four visual-linguistic connections may become functional: letter-phonemic code, whole word-semantic code, whole word-name code, letter sequence-aural syllabic code. The hypothesis was tested that more than one of these visual-linguistic connections must be taken into account in predicting reading achievement. Results showed that the combination of the composite letter-phoneme variable and the composite whole word-semantic code variable accounted for significantly more variance in oral reading than did either single variable at the end of the first grade. Groups with large absolute discrepancy (1 or more standard scores) or small absolute discrepancy (1/3 standard score or less) on corresponding visual and linguistic skills differed significantly in both oral (whole word-semantic code composite) and silent reading (whole word-semantic code and letter sequence-aural syllabic code composites). There was a relationship between the number of large discrepancies and reading achievement. Results are discussed in reference to neuropsychological models of connectionism (Rumelhart & McClelland, 1986) and working brain systems (Luria, 1973).

Child↗