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Biomedical subjects

R H Jones

Publications and source records attributed to R H Jones.

At least 235 records · Page 13Linked to original sources
PubMed1984

Noninvasive determination of exercise cardiac function following Fontan operation.

The purpose of this investigation was to define mechanisms which increase cardiac output during exercise in patients without a functioning right ventricle. Radionuclide studies were performed at rest and during upright bicycle exercise on 16 patients following Fontan procedures and compared to studies in 10 normal children. The mean cardiac index of patients following Fontan procedures was 5.2 +/- 2.0 L/min/m2 (standard deviation) at rest and increased to 9.4 +/- 3.5 L/min/m2 during exercise (p less than 0.0001). Exercise values were similar to those observed in normal children. The mechanisms utilized to achieve high cardiac output following Fontan procedures included an increase in heart rate. Mean systemic ventricular ejection fractions were significantly less than in normal children. The resting ventricular end-diastolic volume and stroke volume indices were above normal and remained constant during exercise to high heart rates. These data clearly document that a large exercise cardiac output can be achieved by patients without a functioning right ventricle.

Adolescent↗
PubMed1983

Evidence concerning the mechanism of insulin-receptor interaction and the structure of the insulin receptor from biological properties of covalently linked insulin dimers.

Covalently linked insulin dimers have been prepared by cross-linking two insulin monomers with a flexible suberoyl chain at either the B1 phenylalanine or the B29 lysine residue. Binding potencies of dimers determined by inhibition of binding of 125I-insulin to isolated rat liver plasma membranes or adipocytes were 2.5-7-fold greater than their abilities to stimulate lipogenesis in adipocytes. Rates of liver plasma-membrane-associated degradation of labelled insulin and dimers, measured by gel filtration, were similar at 37 degrees C. Binding and lipogenesis potencies of dimers prepared by substitution of each monomeric half of an asymmetrical dimer with desoctapeptide insulin, an almost inactive derivative, implicated the B1-cross-linked monomeric half as predominantly interacting with the insulin receptor. These results suggest that (1) dimers bind univalently to a bivalent insulin-receptor complex, in which the two individual binding subunits are arranged with anti-parallel symmetry and (2) the mechanism by which insulin binds and initiates its biological responses requires a conformational change within the insulin-receptor complex and/or in the insulin molecule for full biological expression.

Adipose Tissue↗
PubMed1983

Relation between QRS changes and left ventricular function after coronary artery bypass grafting.

Preoperative and serial postoperative electrocardiograms (ECGs) were reviewed in 104 patients undergoing rest and exercise radionuclide angiocardiography before and 1 to 12 months after coronary artery bypass grafting (CABG). Five patient groups were defined by ECG findings before and after CABG: Group I--normal ECG before and no ECG change after CABG; Group II--prior myocardial infarction by ECG before but no QRS change after CABG; Group III--all patients with a minor QRS change (less than 0.04-second Q wave, loss of R-wave amplitude) after CABG; Group IV--all patients with a major QRS change (greater than or equal to 0.04-second Q wave) after CABG; Group V--all patients without new Q waves or loss of R-wave amplitude but with a major QRS change (conduction disturbance) after CABG. Mean resting ejection fraction changed little after CABG in all groups, although the 0.03 increase in Group I was significant (p less than 0.05). Group IV had the largest decrease in resting ejection fraction after CABG (0.04), but this was not statistically significant. Mean exercise ejection fraction increased significantly (p less than 0.0001) in Groups I, II and III but not in Groups IV and V. QRS changes do not consistently reflect impairment of left ventricular (LV) function after CABG.

Angina Pectoris↗
PubMed1983

Management of cardiac arrest in the community: a survey of resuscitation services.

A survey of the English health regions identified nine ambulance based resuscitation schemes. Their structure and function are heterogeneous and their impact on patient survival is often speculative. There is considerable medical, paramedical, and lay enthusiasm for resuscitation schemes but this cannot be harnessed until medicolegal uncertainties are removed and guidelines for development are set out. Better documentation of the benefits of existing schemes should be undertaken so that advanced training of ambulance personnel can proceed rationally.

Ambulances↗
PubMed1983

Radionuclide left ventricular volume curves in angiographically proved normal subjects and patients with three-vessel coronary disease.

To determine the diagnostic value of measurements obtained from radionuclide left ventricular volume curves, we compared 12 patients with normal coronary arteries (NL) to 12 patients with three-vessel coronary artery disease (3V CAD). Maximum and mean rates of ejection and filling, times of maximum ejection and filling, durations of systole and diastole, and percentages of ejection and filling during each third were measured at rest and during exercise. The only group differences at rest were a 39 msec (p = 0.002) delay in the time of maximal filling and a 6% (p = 0.04) decrease in first third filling fraction in the 3V CAD patients. The overlap in values for these two parameters, however, did not allow good separation of the patients into NL and 3V CAD groups. During exercise, maximal and mean rates of ejection and filling were significantly lower in the 3V CAD group, but these measurements did not improve on the discriminative value of heart rate and ejection fraction alone. Thus, in both the resting and exercise states, measurements of instantaneous changes in left ventricular volume added little diagnostic information.

Aged↗
PubMed1983

Radionuclide analysis of right and left ventricular response to exercise in patients with atrial and ventricular septal defects.

In patients with ventricular or atrial septal defect, the ventricle which is chronically volume overloaded might not appropriately respond to increased demand for an augmentation in output and thereby might limit total cardiac function. In this study we simultaneously measured right and left ventricular response to exercise in 10 normal individuals, 10 patients with ventricular septal defect (VSD), and 10 patients with atrial septal defect (ASD). The normal subjects increased both right and left ventricular ejection fraction, end-diastolic volume, and stroke volume to achieve a higher cardiac output during exercise. Patients with VSD failed to increase right ventricular ejection fraction, but increased right ventricular end-diastolic volume and stroke volume. Left ventricular end-diastolic volume did not increase in these patients but ejection fraction, stroke volume, and forward left ventricular output achieved during exercise were comparable to the response observed in healthy subjects. In the patients with ASD, no rest-to-exercise change occurred in either right ventricular ejection fraction, end-diastolic volume, or stroke volume. In addition, left ventricular end-diastolic volume failed to increase, and despite an increase in ejection fraction, left ventricular stroke volume remained unchanged from rest to exercise. Therefore, cardiac output was augmented only by the heart rate increase in these patients. Right ventricular function appeared to be the major determinant of total cardiac output during exercise in patients with cardiac septal defects and left-to-right shunt.

Adolescent↗
PubMed1983

Optimal frequency locations for estimating model parameters in studies on respiratory control.

Sinusoidal work rate inputs yield a dynamic ventilatory response which can be fitted to a mathematical model. The model structure leads to inferences about the underlying physiology of the respiratory control mechanism. A particular problem of interest in model parameter estimation concerns the location of the test frequencies. The effects of estimating the parameters of a relatively complex model developed by Fujihara et al. using arbitrary frequency locations from a study by Casaburi et al. versus using the frequencies derived from an optimization method presented in a recent paper by Engeman et al. were examined. The Fujihara model is indicated to be much more likely to be justified when optimal sinusoids are used to generate the data than when Casaburi's arbitrary frequencies are used. The implications are that more descriptive models of respiratory control may be developed with the aid of optimal frequency design for the input sinusoids.

Humans↗
PubMed1983

Early assessment of rest and exercise left ventricular function following coronary artery surgery.

Radionuclide assessment of rest and exercise left ventricular function was performed in 14 patients before, eight days after, and three months after coronary artery bypass grafting (CABG). Resting function was unaltered after operation, although mild increases in heart rate and end-diastolic volume were observed on the eighth postoperative day. In contrast, exercise function was significantly improved at both postoperative time periods. Exercise ejection fraction was 0.54 +/- 0.10 before operation, 0.73 +/- 0.12 at eight days, and 0.64 +/- 0.13 at three months. Before CABG, the exercise-induced increase in stroke volume was achieved by an increase in end-diastolic volume, whereas eight days after CABG this increase was achieved by an increase in contractility (systolic blood pressure/end-systolic volume). By three months, both contractility and end-diastolic volume increased with exercise. Thus, improvement in left ventricular function during exercise can be documented as early as eight days after coronary revascularization. This change may be less pronounced after three months of convalescence, but considerable improvement in ventricular function persists compared to preoperative assessment.

Aged↗
PubMed1983

The role of radionuclide angiocardiography in the preoperative prediction of pain relief and prolonged survival following coronary artery bypass grafting.

Radionuclide angiocardiography (RNA) provides noninvasive measurements of left ventricular function during rest and exercise, which appear to reflect the magnitude of fibrosis and ischemia in patients with coronary artery disease. This investigation evaluated the usefulness of these measurements for providing prognostic information, useful in selecting therapy. The RNA study group included 278 patients with a low resting ejection fraction and coronary artery disease documented by angiography. Patients were followed for up to three years to define survival and incidence of complete pain relief. The 172 patients treated medically had less favorable survival and pain relief than the 106 surgically treated patients. In the medically treated patients, a positive RNA defined a subgroup of 113 patients, with a 20% lower 3-year survival than the 59 patients with a negative RNA. Moreover, comparison of patients receiving medical and surgical therapy following a positive RNA documented a clear improvement in both survival and pain relief for those who showed significant ischemia during exercise and subsequently underwent coronary bypass procedures. In patients with a negative RNA, medical and surgical therapy resulted in a similar survival rate and little difference in pain relief. Calculations comparing the maximal potential increase in survival and complete pain relief, using multiple criteria known to provide prognostic information, identified the exercise response on RNA as the single most important variable for selection of therapy. Therefore, the left ventricular response to exercise provides important prognostic information in patients with low resting ejection fractions, and the results of this procedure can be used to define subgroups of patients who will and will not benefit from coronary artery bypass grafting.

Cardiac Catheterization↗
PubMed1983

Comparison of rest and exercise radionuclide angiocardiography and exercise treadmill testing for diagnosis of anatomically extensive coronary artery disease.

The accuracy of rest and exercise radionuclide angiocardiography (RNA) and exercise treadmill testing (ETT) for diagnosis of three-vessel or left main coronary artery disease (extensive CAD) was determined in 544 patients. ETT and RNA sensitivities were similar (88% vs 92%, NS), but ETT was more specific than RNA (46% vs 34%, p less than 0.01). The prevalence of extensive CAD in patients with a positive treadmill (41%) increased only 3% when the RNA was also positive. However, in the 292 patients with a negative or indeterminate ETT, a positive RNA increased this prevalence from 16% to 23%, while a negative RNA decreased this prevalence to 5%. These results support the initial use of ETT followed by RNA if the treadmill is negative or indeterminate for diagnosis in a population with a high prevalence of extensive CAD. This approach separates patients into subgroups with a high or low probability of extensive CAD.

Adult↗
PubMed1983

The use of radionuclide angiography in the diagnosis of coronary artery disease--a logistic regression analysis.

We applied logistic regression analysis to a group of 736 patients with chest pain to determine which radionuclide angiographic (RNA) parameters were most useful in the diagnosis of significant coronary artery disease. The most useful parameters were exercise ejection fraction, exercise heart rate, "ischemia score," and the presence of a regional wall motion abnormality at exercise. Ten clinical variables were used in one logistic regression model to estimate each patient's pretest probability of disease. A second logistic regression model considered these clinical variables and the four important RNA parameters to estimate each patient's posttest probability. These models were applied prospectively to a group of 76 patients with chest pain who did not have a high pretest probability of disease. Twenty-four patients (32%) could be diagnosed with 90% probability; 32 patients (42%) could be diagnosed with 85% probability. RNA testing is therefore helpful in the noninvasive diagnosis of coronary artery disease. However, a majority of patients who do have a low or intermediate pretest probability of disease will require additional testing for a definitive diagnosis.

Cardiac Catheterization↗
PubMed1983

Natural history of cerebral complications of coronary artery bypass graft surgery.

We reviewed 1,669 patients who survived coronary artery bypass graft surgery between 1969 and 1981. A total of 75 cerebral complications were identified, including (1) altered mental state, (2) stroke, and (3) seizure in 64 patients (3.8%). Altered mental state (delirium, hypoxic-metabolic encephalopathy) occurred in 57 (3.4%). Postoperative arrhythmias were associated with an increased risk of altered mental state. Cerebral infarction occurred in 13 (0.8%). Patients who suffered stroke had a higher occurrence of carotid bruits and history of peripheral vascular disease. Seizures occurred in five patients (0.3%). Mortality in patients with a neurologic complication was 29%.

Brain Diseases↗
PubMed1983

Radionuclide angiocardiographic analysis of myocardial function in myotonic muscular dystrophy.

Using radionuclide angiocardiography, we studied cardiac function in 10 men with myotonic muscular dystrophy who had no cardiac symptoms and were less than 50 years of age, comparing resting and exercise performance of the heart. Nine of 10 patients had an abnormality of myocardial function. The interaction of exercise-induced cardiomyopathy with conduction system abnormalities may be important in sudden cardiac dysfunction in patients with myotonic dystrophy.

Adult↗
PubMed1983

Effects of particulate air pollution on asthmatics.

Twenty-four asthmatic subjects in Denver were followed from January through March 1979, a three-month period in which Denver air pollution levels are generally high and variable. Dichotomous, virtual impactor samplers provided daily measurements (micrograms/m3) of inhaled particulate matter (total mass, sulfates, and nitrates) for coarse (2.5--15 micrograms in aerodynamic diameter) and fine fractions (less than 2.5 micrometers). Carbon monoxide, sulfur dioxide, ozone, temperature, and barometric pressure were also measured. Twice daily measurements of each subject's peak expiratory flow rates, use of as-needed aerosolized bronchodilators, and report of airways obstruction symptoms characteristic of asthma were tested for relationships to air pollutants using a random effects model across subjects. During the time actually observed, there were very few days in which high levels of suspended particulates were recorded. Of the environmental variables studied, only fine nitrates were associated with increased symptom reports and increased aerosolized bronchodilator usage.

Adult↗
PubMed1983

Single-dose and seven-day trimethoprim and co-trimoxazole in the treatment of urinary tract infection.

One hundred and sixteen adults with symptoms of acute urinary tract infection were randomly collected into four groups and given single-dose or seven-day treatment with trimethoprim or co-trimoxazole. Of the 105 patients who completed the study, bacterial urinary infection was present in 70 patients (67 per cent). The rates for symptomatic and bacterial cures were high and indistinguishable between the groups, and there was no difference in the rate of recurrence of urinary infection in the six weeks after treatment. Side effects were lower in the group receiving single-dose trimethoprim (P=0.09).

Adolescent↗
PubMed1983

The use of chaperones by general practitioners.

A postal questionnaire was sent to 200 male general practitioners to assess attitudes towards chaperones and the extent of their use when female patients are being examined. The response rate was 85.5 per cent. Of the 171 respondents, 23 (13 per cent) claimed they always use a chaperone and 42 (25 per cent) said they never do. Reported use and non-use were related to the doctor's age and to the size of the practice in which he works. The patient's youth and single marital status are apparently important determinants of the decision to use a chaperone, although many of the general practitioners rely on ;instinct'. Reasons given for non-use included inconvenience and habit. Many of the doctors said they felt the presence of a third party to be detrimental to the doctor-patient relationship and just as many said they believed the chaperone's presence to be beneficial.

Adult↗