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Biomedical subjects

W Ashburn

Publications and source records attributed to W Ashburn.

At least 19 recordsLinked to original sources
PubMed1986

Intraoperative osteoscintigraphy as an aid to bone biopsy.

A new use for intraoperative bone imaging is described. The technique allowed accurate localization of bone pathology for biopsy where plain radiographs and bone morphology were otherwise normal. The technique should increase diagnostic accuracy and eliminate false-negative biopsy results.

Adenocarcinoma↗
PubMed1984

A randomized trial of exercise training in patients with coronary heart disease.

In order to determine whether or not regular exercise could alter myocardial perfusion or function, we randomized 146 male volunteers with stable coronary heart disease to either a supervised exercise program (n = 72) or to a usual care program (n = 74). Subjects underwent exercise tests initially and one year later. Significant differences between the two groups included improved aerobic capacity, thallium ischemia scores, and ventricular function in the exercise intervention group. It was not possible to classify the conditions of patients as to the likelihood of improvement or deterioration. This study demonstrated changes in myocardial perfusion and function in a select group of middle-aged men with coronary heart disease who underwent a medically appropriate exercise program lasting one year, but these changes were relatively modest.

Adult↗
PubMed1984

Individual variability of radionuclide ventriculography in stable coronary artery disease patients over one year.

To determine the individual reproducibility of radionuclide ventriculography over an extended period of time, 33 patients with stable coronary artery disease were studied at rest and during three stages of exercise on two occasions separated by 1 year. The individual interstudy variability of ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume, and cardiac output was determined by calculating the mean and standard deviation of the difference between the individual studies (initial - 1 year). Despite high correlations between an EF measured at study 1 and study 2 of 0.96 at rest and 0.87 during maximal exercise, the individual interstudy difference was 0.01 +/- 0.04 and -0.02 +/- 0.09, respectively. The correlation of percent change in EF from rest to maximal exercise was 0.49 and the individual interstudy differences was -1.2 +/- 19%. Correlations of the EDV were 0.81 at rest and 0.72 during maximal exercise while the individual difference was 0.7 +/- 38 and -0.8 +/- 49 ml, respectively. Considering two standard deviations as the confidence limits for a true change, an EF change of 8 EF units (0.08) at rest and 18 (0.18) during exercise, and EDV changes of approximately 100 ml are needed in an individual to state with confidence that the observed difference between the two studies are true changes and not the result of technologic variability. Because of the large individual interstudy variability in EF and volume measurement, caution must be taken in assuming that any change over a year is due to more than technique variability.

Adult↗
PubMed1983

Pulmonary blood volume: relationship to changes in left ventricular end-diastolic pressure during atrial pacing.

Little data exist about the relationship between changes in cardiac end-diastolic pressure and changes in pulmonary blood volume. To assess this relationship, we studied 11 patients with coronary heart disease during atrial pacing in an attempt to produce multiple pressure-volume points. During catheterization, we obtained Millar pressure recordings of end-diastolic pressure along with equilibrium radionuclide angiograms. Cardiac output, ejection fraction, and pulmonary blood volume were obtained by means of recently validated radionuclide techniques. During pacing, substantial changes in pulmonary blood volume occurred only with marked increase in end-diastolic pressure volume (greater than or equal to 15 mm Hg) and rarely exceeded 15% of control pulmonary blood volume. Cardiac output did not change, while ejection fraction declined during pacing. There was a fair correlation between the absolute change in pulmonary activity (or pulmonary blood volume) or the percentage of change in pulmonary activity over the control value with end-diastolic pressure when all the data points were evaluated (n = 74, r greater than 0.70). However, the scatter in the data precluded making accurate estimates of pressure changes from changes in radionuclide volume changes. We conclude that large changes in cardiac filling pressure must occur during atrial pacing, where cardiac output does not change, before visible pulmonary blood volume changes occur. This may limit the extrapolation of presumed pressure changes from known pulmonary blood volume when changes are small.

Blood Pressure↗
PubMed1982

Noninvasive assessment of changes in myocardial perfusion and ventricular performance following exercise training.

Seventeen coronary patients (CAD) underwent thallium (TI-201) treadmill and radionuclide (RNV) ejection fraction supine bicycle testing before and after 5.6 +/- 1.6 (mean +/- SD) months of an exercise program. Thallium data were assessed both using analog images and a computerized circumferential profile technique. Patients exercised on the treadmill to a higher workload after the exercise program, but achieved a similar pressure-rate product. When interpreting the analog thallium images, only 50% agreement was obtained for the assessment of changes in myocardial perfusion (pre/post-training). The computer technique, however, had low inter-intraobserver variability (6%) and better agreement (90.5%). Using the circumferential profile method, five patients improved (a total of 11 regions) and one patient worsened (with two regions). Before the exercise program, the ejection fraction (EF) response to supine bike exercise was normal (an increase greater than 11%) in four, flat in seven, and severely abnormal (a decrease of more than 4%) in six patients. After the exercise program, even though achieving similar or higher pressure-rate products, six patients improved their EF response, nine did not change, and two worsened. Of the five patients who improved their thallium images, one improved his EF response, two remained normal, and two did not change. One patient worsened both his thallium study and the EF response after the exercise program. Changes in thallium exercise images and the EF response to supine exercise occurred in our patients after an exercise program, but were not always concordant. Indeed, of five patients with exercise-induced ischemic ST changes before and after training, the EF response improved in three whereas myocardial perfusion was unchanged. Reasons for this lack of agreement are discussed, and have been considered in the planning of a randomized trial of the effects of an exercise program on myocardial perfusion and function.

Adult↗
PubMed1982

Postural changes in pulmonary blood flow in pulmonary hypertension: a noninvasive technique using ventilation-perfusion scans.

To determine whether postural changes in ratio of upper to lower (U:L) zone pulmonary blood flow reflect pulmonary arterial pressures, we used pulmonary perfusion photoscintigraphy to study 12 normal subjects and 10 patients with precapillary pulmonary hypertension (eight classified as "primary" and two as thromboembolic). All patients underwent right-heart catheterization and measurement of pulmonary arterial systolic, diastolic, mean and capillary (wedge) pressures. The distribution of perfusion was then assessed in the supine and erect positions after i.v. injection of technetium-99m-labeled, macroaggregated albumin. Perfusion distribution was corrected for lung volume by xenon-133 equilibrium ventilation scans. In normal subjects, the U:L lung zone perfusion ratio decreased by 70.7 +/- 12.2% with the change in position. The patient group differed (p less than 0.0001) from normal subjects in that there was only a 19 +/- 17.4% shift of U:L ratio with the postural change. The mean pulmonary arterial pressure in the patient groups was 50 +/- 24.2 mm Hg. The postural change in U:L zone ratio correlated significantly with the mean pulmonary arterial pressure (r = -0.84, p less than 0.01) pulmonary arterial systolic (r = -0.83, p less than 0.01) and diastolic pressures (r = -0.72, p less than 0.05) and with the pulmonary vascular resistance (r = -0.74, p less than 0.02). No correlation was found with other hemodynamic, spirometric or blood gas data. We conclude that the postural shift in U:L ratio warrants further exploration as a noninvasive approach for detecting and quantifying pulmonary hypertension.

Adult↗
PubMed1981

Rest and exercise electrocardiograms and radionuclides in patients presenting for cardiac rehabilitation.

The rest and exercise ECG, 201thallium myocardial scintigram (201T1), and radionuclide ventriculography are noninvasive procedures which can be used to evaluate myocardial damage and ischemia. To compare these procedures and to obtain baseline information, 85 male patients with coronary heart disease were evaluated prior to beginning an exercise program. Findings at rest included Q waves or bundle branch block in 54%; 47% had 201T1 redistribution defects and 33% an abnormal ejection fraction (EF). Of the 39 patients with normal ECGs, 31 had no 201T1 defects and only of these 31 (3%) had an abnormal EF. Abnormal EF or 201T1 redistribution defects did not occur in patients without a history of myocardial infarction. Abnormal resting EF occurred in 63% of patients with abnormal versus 7% of those with normal 201T1 redistribution scans. Exercise test results included an abnormal ST-segment response in 80%, an abnormal EF response in 65%, and a 201T1 ischemic defect in 37%. Twenty patients had exercise-induced ST elevation, and this phenomenon was more related to ventricular aneurysms than to ischemia. 201Thallium imaging, radionuclide ventriculography, and the ECG provide results regarding myocardial damage that agree by more than chance, while the exercise induced ST-segment changes did not agree with the radionuclide indications of exercise-induced ischemia.

Adult↗
PubMed1981

Evaluation of left ventricular function in chronic pulmonary disease by exercise gated equilibrium radionuclide angiography.

To assess left ventricular (LV) response to supine bicycle exercise, we studied 10 normal (group 1). 10 patients with coronary artery disease (CAD) (group 2), 12 patients with severe obstructive lung disease (COPD) (group 3), and eight patients with both CAD and COPD (group 4) by gated equilibrium radionuclide angiography. Most individuals in all groups also had pulmonary catheter-obtained measurements of LV filling pressures during exercise. Normal individuals increased their ejection fraction (EF) during exercise by increasing stroke volume (SV) and reducing end-systolic volume (ESV) without changing end-diastolic volume (EDV); pulmonary artery (PAP) and wedge (PAW) pressures were unaltered. CAD patients (group 2) showed no change in EF with increased EDV, ESV, SV, and PAW. COPD patients (group 3) exhibited decreases in EDV, ESV, and SV, accounting for abnormal EF responses in 6 of 12; PAW was unchanged and the marked elevation of PAP correlated with reduced EDV. Group 4 patients (CAD plus COPD) had abnormal EF responses with increased EDV and ESV without change in SV. Thus an abnormal LV function response to exercise in COPD patients may be multifactorial, thereby indicating the possible need for therapeutic modalities in addition to those employed in alleviating pulmonary parenchymal disease.

Adult↗
PubMed1981

Agreement in human interpretation of analog thallium myocardial perfusion images.

To assess the agreement of human interpretation of analog thallium myocardial perfusion images, four experienced interpreters evaluated 100 images on two occasions using a form designed to limit reader variability. A high intraobserver agreement (agreement by same observer at separate times) of 89--93% was found when films were interpreted as normal or abnormal (a dichotomous decision). Interobserver agreement for a majority grouping of observers (three or four) was 75% for an abnormal and 68% for a normal interpretation. However, agreement ranged from 11--79% when interpreters were asked to read the anatomic location of defects. Posterior and lateral wall defects were interpreted with the least amount of agreement. These results indicate that caution must be taken when interpreting defect location. Using a scale of 1--10 to grade the severity of a defect, correlations of 0.82--0.86 were found when reading defects in the lateral and anterior projections. Higher correlations, from 0.86--0.94, were found in left anterior oblique views. Use of reporting forms with specific criteria, multiple observers at one occasion, and/or computer processing may improve agreement. A brief review of the agreement of cardiology testing procedures is also presented.

Angina Pectoris↗
PubMed1981

Left ventricular size and function after subcutaneous administration of terbutaline.

To assess the response of the left ventricle to subcutaneously administered terbutaline sulfate, a proposed beta-2 selective agonist, we evaluated 12 patients who had suffered previous myocardial infarctions using equilibrium radionuclide angiography. Six patients (group 1) had normal global left ventricular ejection fraction at rest less than 0.49). All patients had a marked decline in end-diastolic volume and end-systolic volume with a significant (P less than 0.01) increase in ejection fraction after terbutaline injection. Cardiac output increased 30 percent in group 2 patients because of an increase in stroke volume, with little change in heart rate (plus or minus 3.1 beats per minute, P equals NS). Cardiac output increased 7 percent in the patients in groups 1, due primarily to an increase in heart rate in 7 beats per minute (+9 percent) with little change in stoke volume. Systemic vascular resistance decreased significantly more in the patients with compensated heart failure than the subjects in group 1 (342 plus or minus 84 vs 90 plus or minus 35 dynes-sec cm(-5), P less than 0.05). We conclude that terbutaline exerts its most beneficial effect on the left ventricle in patients with depressed resting global function, and may prove to be a useful agent in the treatment of congestive heart failure.

Aged↗
PubMed1981

A method for the estimation of right ventricular volume by equilibrium radionuclide angiography.

To develop a method for estimating right ventricular volume and to assess right ventricular volume at rest, we studied 45 persons with equilibrium radionuclide angiography. The study group comprised 15 normal control subjects (5 with atypical chest pain and normal coronary angiograms) and 30 patients with coronary heart disease (CHD). Each coronary patient and 5/15 control subjects had both right and left heart catheterization studies with intracardiac pressure measurements within 24 hours of the radionuclide study. Using a previously described method for generating right ventricular volume curves, we used the counts at end-diastole, corrected for frame time, the total number of processed heart beats, and blood radioactivity to derive right ventricular end-diastolic volume units. All normal controls (group 1) had a right ventricular ejection fraction greater than or equal to 0.40, with a right ventricular volume index less than or equal to 5.8. The CHD patients consisted of two subgroups: group 2 (N = 20) and group 3 (N = 10), with right ventricular end-diastolic pressures less than 10 mm Hg and greater than or equal to 10 mm Hg, respectively. In group 2, 19/20 had a normal right ventricular ejection fraction, and 18 had a normal end-diastolic volume. In group 3, 4/10 patients had a depressed ejection fraction (less than .40) and 9/10 an increased end-diastolic volume. We conclude that right ventricular volume can be estimated with radionuclide angiography, and that dilation may precede depression of the right ventricular ejection fraction in some patients with CHD.

Angiography↗
PubMed1980

Left ventricular ejection fraction changes during recovery from treadmill exercise: a preliminary report of a new method for detecting coronary artery disease.

To test the value of combining treadmill exercise with radionuclide angiography for detecting exercise-induced left ventricular dysfunction, ejection fractions were calculated at rest, peak supine bicycle exercise, and during three supine post-treadmill recovery periods (2-4 min, recovery 1;4-6 min, recovery 2;8-10 min, recovery 3) in ten coronary artery disease patients and eight normal subjects. Both the normal subjects and coronary artery disease patients had normal resting ejection fractions (greater than 0.50). In the normal subjects the mean ejection fraction increased significantly (p less than 0.005) from rest (0.61 +/- 0.03) to peak supine bicycle exercise (0.71 +/- 0.04), and the mean ejection fraction also remained significantly higher (p less than 0.005) at rest than during 10 min post-treadmill exercise. However, the coronary artery disease patients did not significantly change the mean ejection fractions from rest (0.59 +/- 0.06) to peak supine bicycle exercise (0.55 +/- 0.08), and the average ejection fraction during each one of the post-treadmill recovery periods was not significantly different from rest. At the third recovery period all the normals but no coronary artery disease patients had higher ejection fraction than the resting ejection fraction. We thus conclude that the magnitude of change in ejection fraction from rest to 8-10 min post-treadmill exercise in patients with normal resting ejection fraction may be helpful in identifying those with coronary disease.

Angiocardiography↗
PubMed1980

Improvement in ventricular function during exercise studied with radionuclide ventriculography after cardiac rehabilitation.

A heterogeneous group of 19 consecutive patients with coronary artery disease were studied with radionuclide ventriculography before and after a mean of 6 months of exercise training. Ejection fraction was measured at rest, at matched submaximal supine work loads and during maximal supine bicycle exercise. After training there was no change in mean ejection fraction at rest or during maximal exercise, but a higher maximal mean systolic blood pressure, heart rate and work load were achieved. At equivalent submaximal work loads after training, similar levels of mean heart rate and systolic blood pressure were reached but a statistically greater mean ejection fraction was obtained. These preliminary results suggest that exercise training may improve cardiac function during exercise in selected patients with coronary disease. A randomized study using similar techniques has been initiated.

Adult↗