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Biomedical subjects

J R Stratton

Publications and source records attributed to J R Stratton.

88 records · Page 5Linked to original sources
PubMed1983

Natural history of platelet deposition on Dacron aortic bifurcation grafts in the first year after implantation.

This study defined the dynamics of platelet deposition on Dacron arterial grafts up to 1 year after implantation in human subjects. Indium-111 platelet imaging was performed on 8 men 1 to 2 weeks after graft implantation and on 5 of these patients at a mean of 31 weeks (range 28 to 34) and again at 55 weeks (range 50 to 62). Serial imaging was performed at 24 to 96 hours after platelet labeling and injection in each study. Quantitative analysis was performed using a graft/blood ratio that compared background-corrected indium-111 platelet activity in the graft region to whole-blood indium-111 platelet activity. Additionally, blinded qualitative visual analysis of the images compared graft activity with the activity in adjacent native arteries. The mean of all graft/blood ratios (24, 48, 72, and 96 hours) progressively decreased from 4.4 +/- 2.1 (+/- 1 standard deviation) at 1 to 2 weeks to 3.0 +/- 1.8 at 31 weeks (p = 0.002). There was no further decrease at 55 weeks (2.8 +/- 2.0). For comparison, 12 normal subjects without grafts had a mean ratio of 1.8 +/- 0.7. Visual analysis detected platelet deposition in 7 of 8 grafts at 1 to 2 weeks, 4 of 5 at 31 weeks, and 4 of 5 at 55 weeks. Deposition decreased qualitatively in 2 of 5 patients at late study. It is concluded that there is consistent, early platelet deposition on Dacron grafts in man. Although deposition decreases over 31 weeks, it remains readily detectable in most patients at 1 year. These findings suggest absent or incomplete endothelialization of the graft flow surface in humans in the first year after implantation.

Aged↗
PubMed1983

Comparative plasma catecholamine and hemodynamic responses to handgrip, cold pressor and supine bicycle exercise testing in normal subjects.

Serial hemodynamic and plasma catecholamine responses were compared among 10 healthy men (27 +/- 3 years) (+/- 1 standard deviation) during symptom-limited handgrip (33% maximal voluntary contraction for 4.4 +/- 1.8 minutes), cold pressor testing (6 minutes) and symptom-limited supine bicycle exercise (22 +/- 5 minutes). Plasma catecholamine concentrations were measured by radioenzymatic assays: ejection fraction and changes in cardiac volumes were assessed by equilibrium radionuclide angiography. During maximal supine exercise, plasma norepinephrine and epinephrine concentrations increased three to six times more than during either symptom-limited handgrip or cold pressor testing. Additionally, increases in heart rate, systolic blood pressure, rate-pressure product, stroke volume, ejection fraction and cardiac output were significantly greater during bicycle exercise than during the other two tests. A decrease in ejection fraction of 0.05 units or more was common in young normal subjects during the first 2 minutes of cold pressor testing (6 of 10 subjects) or at symptom-limited handgrip (3 of 10), but never occurred during maximal supine bicycle exercise. The magnitude of hemodynamic changes with maximal supine bicycle exercise was greater, more consistent and associated with much higher sympathetic nervous system activation, making this a potentially more useful diagnostic stress than either handgrip exercise or cold pressor testing.

Adult↗
PubMed1982

Detection of left ventricular thrombus by two-dimensional echocardiography: sensitivity, specificity, and causes of uncertainty.

To define the sensitivity, specificity and predictive accuracy of two-dimensional echocardiographic detection of left ventricular thrombus, the echocardiograms of 78 patients who had independent proof of the presence or absence of a left ventricular thrombus were interpreted without knowledge of any clinical data. The presence of thrombus was established by autopsy in four patients, by aneurysmectomy in three, and by indium-111 platelet imaging in 15; the absence of thrombus was proved by autopsy in 55 patients and by aneurysmectomy in one patient. The characteristics of true-positive and false-positive echocardiograms, interobserver variability, and clinical features associated with proved thrombus were also defined. The echocardiogram was positive for thrombus in 22 patients, equivocal in seven and negative in 49. For detection of thrombus, a positive or equivocal echocardiogram had a sensitivity of 95% (21 of 22), a specificity of 86% (48 of 56), and a predictive value of 72% (21 of 29); the predictive value of a negative study was 98% (48 of 49). Considering positive and equivocal studies separately, the predictive value of a positive study was 86% (19 of 22), while that of an equivocal study was only 29% (two of seven). Compared with patients who had no thrombus, patients with proved thrombus had a higher prevalence of electrocardiographic transmural anterior infarction (86% vs 13%), left ventricular aneurysm (73% vs 5%), and clinical systemic emboli (36% vs 7%) (all p less than 0.05). These clinical features help to identify a subset of patients most likely to have left ventricular thrombi who may benefit from echocardiography. Two-dimensional echocardiography is highly sensitive in detecting left ventricular thrombus, but false-positive studies are relatively common. Several echocardiographic criteria derived from analysis of the true and false positives in this study may help minimize diagnostic errors.

Diagnosis, Differential↗
PubMed1981

Detection of left ventricular thrombi with radionuclide angiography.

Apparent filling defects compatible with left ventricular thrombus are occasionally noted in equilibrium radionuclide angiocardiograms. To define the usefulness of the radionuclide angiogram in detecting left ventricular thrombus, the anterior and left anterior oblique radionuclide angiograms of 39 patients with proved presence or absence of thrombus were blindly interpreted. The presence of thrombus was proved at autopsy in 5 patients, at cardiac operation in 2, or on indium-111 platelet imaging in 6; the absence of thrombus was proved at autopsy in 24 or at cardiac operation in 2. Overall, 13 radionuclide angiograms were interpreted as positive (n = 10) or equivocally positive (n = 3) for thrombus, and 26 studies were judged negative. The sensitivity of a positive or equivocally positive radionuclide angiogram for detection of thrombus was 77 percent (10 of 13 patients), the specificity 88 percent (23 of 26 patients), the positive predictive value 77 percent the negative predictive value 88 percent. If the three equivocal studies are instead considered negative for thrombus, the sensitivity was 62 percent, the specificity 92 percent, the positive predictive value 80 percent and the negative predictive value 93 percent. All thrombi were visualized in the anterior view in an area of akinetic or dyskinetic wall motion. A small group of 13 patients (8 with thrombus, 5 without) underwent two dimensional echocardiography, which was 100 percent sensitive and specific. The finding of a discrete filling defect or squared or cutoff ventricular apex in an area of abnormal wall motion in the anterior view of the radionuclide angiogram should suggest the diagnosis of ventricular thrombus, which may be confirmed by other noninvasive studies.

Autopsy↗
PubMed1981

Left ventricular thrombi: in vivo detection by indium-111 platelet imaging and two dimensional echocardiography.

Indium-111 platelet imaging, which can identify sites of active intravascular platelet deposition, and two dimensional echocardiography, which can identify intracardiac masses, can both be used to detect left ventricular thrombi noninvasively. We compared these techniques in 44 men at risk for thrombi from remote transmural myocardial infarction (31 patients) or cardiomyopathy (13 patients). All 44 patients underwent platelet imaging; 35 underwent echocardiography. On platelet imaging nine patients had thrombi and one had a possible thrombus. Of these 10 studies, none were positive at 2 hours, 5 were positive at 24 hours and all were positive 48 or 72 hours after platelet labeling. Nine of these patients underwent echocardiography, and all had an intraventricular mass. The findings on platelet scanning were negative in six patients who had positive (four patients) or equivocally positive (two patients) findings on echocardiography. All patients with thrombi detected by either noninvasive method had transmural anterior myocardial infarction with ventricular aneurysm. Of the seven patients who underwent cardiac surgery or autopsy, three had thrombi. Platelet imaging failed to identify one thrombus in a patient in whom imaging was performed only at 24 hours after labeling. There were no false positive platelet images in this group. Five of these seven patients (two with thrombi, three without) underwent echocardiography; in all cases the echocardiographic findings agreed with the pathologic findings. Both platelet imaging and echocardiography detect ventricular thrombi. Platelet imaging may detect only the most hematologically active thrombi. Both techniques may help define patients at risk of embolization and may be useful for in vivo assessment of antithrombotic drugs.

Aged↗
PubMed1981

Indium-111 platelet imaging for detection of platelet deposition in abdominal aneurysms and prosthetic arterial grafts.

Thirty-four platelet imaging studies were performed in 23 patients to determine whether platelet deposition could be detected in patients with vascular aneurysms (18 patients) or in patients in whom Dacron prosthetic grafts had been place (5 patients). In patients in whom abnormal platelet deposition was detected, the effect of administration of platelet-active drugs on platelet deposition was examined. Of the 18 patients with an aneurysm, 12 had positive studies on initial imaging and 2 had equivocally positive images. Of five patients with Dacron arterial grafts in place, four had diffuse platelet deposition in the grafts; the fifth patient had platelet deposition only in a pseudoaneurysm. Eight patients with an abdominal aneurysm and positive or equivocally positive baseline images were restudied during platelet-active drug therapy either with aspirin plus dipyridamole (seven patients) or with sulfinpyrazone (four patients). No patient studied during treatment with aspirin plus dipyridamole had detectably decreased platelet deposition compared with baseline determinations. In contrast, two of four patients studied while receiving sulfinpyrazone showed decreased platelet deposition. Thus, platelet imaging may be of value for studying platelet physiology in vivo and for assessing platelet-active drugs and the thrombogenicity of prosthetic graft materials in human beings.

Abdomen↗
PubMed1981

Seven-pinhole emission tomography with thallium-201 in patients with prior myocardial infarction.

Thirty-six patients with prior myocardial infarction, and 14 patients without, had myocardial imaging at rest using both seven-pinhole emission tomography and planar imaging with thallium-201. The sensitivity and specificity of the two approaches for the detection of prior myocardial infarction were compared. Qualitatively, planar imaging yielded sensitivities of 69% (25 of 36) and 80% (29 of 36) with Polaroid and video display formats, respectively. A semiquantitative analysis gave a sensitivity of 75% (27 of 36). Specificities for these three planar approaches were, respectively, 100% (14 of 14), 93% (13 of 14), and 71% (10 of 14) for the Polaroid, video, and semiquantitative analyses. Seven-pinhole tomography had a sensitivity of 83% (30 of 36) by qualitative or visual inspection and 86% (31 of 36) by semiquantitative analysis. Specificities by these two techniques were 71% (10 of 14) and 57% (8 of 14). There were no statistically significant differences in either sensitivity or specificity between the planar and tomographic approaches. Repeat seven-pinhole images were identical in 95% (46 of 48) of patients, showing that reproducibility was satisfactory. We conclude that the seven-pinhole tomographic approach has no advantage over standard planar imaging in the detection of prior myocardial infarction.

Adult↗
PubMedDate not supplied

Cardiac receptor physiology and its application to clinical imaging: present and future.

Both gamma imaging and positron emission tomography (PET) imaging of cell surface receptors have become possible through the development of agonists and antagonists with high specific radioactivity and high specificity for the receptors. An understanding of the physiology of the cardiac receptor system is essential to comprehending receptor imaging. The complexity of the physiologic information developed over the past decade has been compounded by the concomitant discovery of additional receptor subtypes. The following is a review of a select group of cardiac receptors and their regulation-namely, adrenergic, muscarinic-cholinergic, adenosine, and angiotensin I and II receptors. The role of imaging regional receptor localization and function in providing new insights into cardiac pathology and therapeutic avenues is explored.

Autonomic Nervous System↗
PubMedDate not supplied

Platelet deposition at carotid endarterectomy sites in humans.

Following carotid endarterectomy, early postoperative thrombosis or late restenosis occurs in up to 20% of vessels. Both complications may be related to platelet mechanisms. To assess platelet deposition at endarterectomy sites, we injected indium-111 labelled platelets in 24 men less than 30 minutes after carotid endarterectomy, with subsequent imaging 24-96 hours later. To determine if deposition decreased over time, 12 patients had follow-up studies 0.5-24 months later. For comparison, 2 control groups were studied: 1) patients with noncarotid surgery (n = 6) and 2) normal young subjects without endarterectomy and without evidence of carotid disease (n = 12). Quantitative analysis was performed performed using a deposition index that compared activity in operated with unoperated sites in surgical patients or activity in the right with left carotid arteries in normal subjects. Patients with recent endarterectomy had a mean deposition index of 1.7 +/- 0.5 (range 1.2-3.5) compared with a similarly determined ratio of 1.1 +/- 0.1 in normal subjects and 1.2 +/- 0.1 in the surgical controls (both p less than or equal to 0.05 vs. acute endarterectomy). At follow-up after endarterectomy, the mean deposition index decreased to 1.0 +/- 0.1, documenting reduced platelet deposition over time. We conclude that the arterial injury of carotid endarterectomy results in early platelet deposition, which is no longer present in most patients who are studied late. These findings suggest a reduction in platelet thrombus formation with time and are compatible with reendothelialization of the endarterectomized surface. This model may be useful for the in vivo assessment of therapies designed to reduce platelet accumulation following endothelial injury in humans.

Aged↗
PubMedDate not supplied

Decreased numbers of platelet alpha-adrenergic binding sites in diabetes mellitus.

Eleven men with diabetes mellitus were compared with 45 male controls for platelet alpha-adrenergic binding sites by using [3H]dihydroergocryptine (DHE) as the radioligand antagonist. There was no difference between the two for binding affinity, but the number of sites was 430 +/- 30 (means +/- SEM) for diabetic subjects and 574 +/- 29 for controls (P = .005). Decreased sites were related to increased glycosylated hemoglobin levels (P = .002). There was no relationship between the decreased sites and catecholamine levels, duration of disease, body weight, or fasting blood sugar. Hence, binding sites were inversely related to control, but further studies are needed to define the pathophysiologic significance of this.

Adult↗