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Biomedical subjects

L J Mahar

Publications and source records attributed to L J Mahar.

13 recordsLinked to original sources
PubMed1987

Tc-99m tertiary butyl isonitrile: a preliminary clinical study of a new myocardial imaging agent in patients with chest pain.

Tc-99m is a preferred agent for nuclear imaging. Tc-99m tertiary butyl isonitrile (Tc-99m-TBI) is the first of a family of lipophilic cations which allow effective imaging of the human myocardium. Twenty-one patients scheduled for coronary angiography for the investigation of their chest pain were studied after injections of this tracer given during exercise, and on a separate visit, at rest. Despite high uptake in the liver and transiently in the lungs, high quality gated images were obtained allowing the assessment of both myocardial uptake and wall motion. The findings corresponded closely with angiographic and ventriculographic assessment of coronary artery disease and myocardial infarction. Redistribution of Tc-99m-TBI was shown to occur in ischemic myocardium analogous to that occurring with thallium-201 (TI-201). Similar agents with more favourable properties may well replace TI-201 as the myocardial imaging agent of choice in the near future.

Angina Pectoris↗
PubMed1985

Plasma histamine levels following administration of radiographic contrast media.

The effect of two conventional high-osmolality and two new low-osmolality contrast media on plasma histamine levels has been examined. The study population included 25 patients undergoing intravenous urography with Urovison 58% (sodium and meglumine diatrizoate), 24 patients receiving intravenous Hexabrix 320 (sodium and meglumine ioxaglate) for urography, 16 patients receiving intravenous Iopamiro 370 (iopamidol) for urography and 12 patients receiving Urografin 76% (sodium and meglumine diatrizoate) for coronary angiography. Seventy-four percent of the 77 patients studied suffered adverse reactions ranging from a feeling of warmth and nausea to laryngeal oedema and bronchospasm. Hexabrix 320 and Iopamiro 370 were associated with the least patient discomfort. All contrast agents usually produced a rise in plasma histamine following injection (Iopamiro 370 causing the least change) and the histamine levels then fell towards preinjection values over a space of about 10 minutes. No relationship was observed between the magnitude of the increase in histamine and the severity of the reaction that occurred. However, a relationship was suggested between the mean peak plasma histamine level achieved and the occurrence of a Grade II reaction (i.e., dry retching/vomiting, mild urticaria or rash). These findings raise the probability that histamine contributes to the more severe grades of reaction to radiographic contrast media.

Contrast Media↗
PubMed1984

Three dimensional reconstruction of the left ventricle from four anatomically defined apical two-dimensional echocardiographic views.

A method is described for three dimensional reconstruction of the left ventricle which uses four anatomically defined apical views. It is shown that the algorithms developed for reconstruction and volume estimation provide accurate results when applied to planar views with accurately defined boundaries. The linear regression equation was y = -6.32 + 1.04x, with SEE = +/- 3.4 ml, r = 0.999. For both "in vitro" and "in vivo" studies this method is found to be better than various geometrical models used to estimate volumes from two dimensional tomographic or projection views. The linear regression equation of in vitro fluid volume on volume estimate is y = 8.44 + 0.68x, with SEE = +/- 4.9 ml, r = 0.988. For pooled end diastolic and end systolic volumes (EDV and ESV) determined by three dimensional reconstruction (3-DR) and angiography the linear regression equation is y = 54.50 + 0.50x, with SEE = +/- 33.5 ml, r = 0.670. For stroke volume (SV), the regression equation is y = 21.10 + 0.40x, with SEE = +/- 12.8 ml, r = 0.750, and for ejection fraction (EF) it is y = 1.10 + 0.70x, with SEE = +/- 7.8%, r = 0.840. In patients with ischemic heart disease, the method presented is shown to be better than existing methods of volume estimation. Three dimensional perspective images can be plotted in any orientation as a visual aid to the cardiologist. In vivo studies demonstrate the feasibility of 3-DR, from anatomically defined apical views, in the clinical setting.

Cardiac Volume↗
PubMed1983

The role of adrenal medullary catecholamine release in the response to a cold pressor test.

We studied the effects of a cold pressor test on the plasma catecholamine levels of ten patients undergoing coronary angiography, to determine whether the pressor changes were related to adrenergic activity. To investigate the relative contribution of adrenal medullary catecholamine release, we subjected two adrenalectomised volunteers to the same test. Arterial blood was assayed for dopamine (DA), adrenaline (A) and noradrenaline (NA). We found significant rises in the levels of all three catecholamines in the angiography patients, accompanied by a significant elevation in arterial blood pressure. In both the adrenalectomised patients a rise in blood pressure was seen but no significant rise in plasma catecholamines could be demonstrated. We postulate that although adrenal medullary catecholamine release occurs in response to the cold pressor test, the blood pressure elevation is independent of such adrenal activity. Sampling radial arterial blood may not reflect changes in plasma levels of peripherally released NA.

Adrenal Medulla↗
PubMed1979

Primary cardiac myxosarcoma in a child.

This is a detailed clinical and autopsy documentation of a rare entity--primary cardiac myxosarcoma in a 29-month-old girl. The patient had sudden onset of right hemiplegia and angiographic evidence of multiple occlusions of the left middle cerebral artery. Subsequent M-mode and sector echocardiography showed a mobile, pedunculated left atrial tumor, which was excised. No other tumor mass was noted at the time of surgical exploration, and postoperatively, the patient received a course of chemotherapy (vincristine, dactinomycin, and cyclophosphamide). After a temporary improvement in her condition, the patient died following several days of rapid deterioration; this was 3 months after the onset of symptoms. Autopsy showed that death was due to brainstem herniation secondary to massive infiltration of the brain by tumor, and there were also widespread systemic metastases.

Brain↗
PubMed1978

Perioperative myocardial infarction in patients with coronary artery disease with and without aorta--coronary artery bypass grafts.

The incidence of perioperative myocardial infarction (MI) was examined in 148 patients with known coronary artery disease (CAD) who underwent 226 noncardiac surgical procedures. In 168 operations in 99 patients who had prior coronary artery bypass grafting (CABG) there were no perioperative MI's whereas in the 49 patients who had not undergone prior CABG who underwent 58 noncardiac operations, there were three MI's (5 percent). The lower (p less than 0.02) incidence of perioperative MI in patients with CAD who had had prior CABG suggests a protective effect for subsequent noncardiac operation, which could not be explained by other differences in cardiac status between the groups. All three MI's occurred in patients with three-vessel CAD, evidence that this should be added to prior MI as a significant risk factor. The study indicates also that patients with prior CABG have less risk of MI during and following anesthesia and noncardiac operation than do patients without CABG who have had a previous MI.

Adult↗
PubMedDate not supplied

Idiopathic orthostatic hypotension controlled with a monoamine oxidase inhibitor and 9-alpha-fluorohydrocortisone.

A case of orthostatic hypotension with autonomic failure is presented, and the patient's clinical response to the combined regime of a monoamine oxidase inhibitor and 9-alpha-fluorohydrocortisone is discussed. This therapy provided a relatively convenient means of alleviating the patient's symptoms and appears to be of considerable value in the management of orthostatic hypotension. However, close patient supervision is essential when these drugs are used as they cause hypertension in the supine position in subjects with poor baroreceptor function.

Blood Pressure↗
PubMedDate not supplied

The effects of exercise on ventilation-perfusion relationship in patients with mitral stenosis.

Exercise limitation is common in patients with chronic pulmonary venous hypertension. One postulated mechanism is ventilation-perfusion inequality secondary to vascular congestion and edema formation. To investigate this possibility, five patients with symptomatic, chronic mitral stenosis were studied at rest, during 10 min of steady-state exercise and during recovery from exercise. Both conventional indices of gas exchange and the multiple inert gas elimination method were used. Hypoxemia was not present in patients at any stage in the study and negligible shunt or low VA/Q lung units were demonstrated by the inert gas method. Instead, regions with high VA/Q ratio appeared toward the end of exercise and immediately after exercise. We postulate that this was the result of a marked redistribution of pulmonary blood flow, possibly due to an accumulation of interstitial edema fluid. It is concluded that the excessive ventilatory response to exercise observed in patients with mitral stenosis may, in part, be explained by an unequal distribution of ventilation and perfusion.

Adult↗