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Biomedical subjects

M O'Rourke

Publications and source records attributed to M O'Rourke.

At least 19 recordsLinked to original sources
PubMed1991

High-dose 24-hour infusion of 5-fluorouracil in metastatic prostate cancer. A phase II trial of the Piedmont Oncology Association.

Thirty-two patients with metastatic carcinoma of the prostate refractory to endocrine therapy were entered on trial. No patient entered in the study had prior chemotherapy. Patients were treated with 5-fluorouracil given at a dosage of 4 gm/m2 over a 24-hour period every 2 weeks. Of the 27 patients evaluable for response, there were no complete or partial remissions, but 9 (33%) had a stable disease. The 95% confidence interval for complete and partial response in this series (0 of 27 patients) is 0.0-12%. Myelosuppression and gastrointestinal toxicity was moderate. Two patients, however, experienced major but completely reversible neurotoxicity, including 1 with cerebellar ataxia and 1 with memory loss and stroke-like symptoms. These data indicate that high-dose fluorouracil used in this dosage and schedule is ineffective in the therapy of advanced carcinoma of the prostate.

Adenocarcinoma↗
PubMed1991

Effect of aging on aortic morphology in populations with high and low prevalence of hypertension and atherosclerosis. Comparison between occidental and Chinese communities.

A comparative morphologic study of aortic changes with aging was conducted in different populations in an attempt to separate the effects of hypertension and atherosclerosis. Chinese and the occidental populations were chosen, as they are known to have a high prevalence of hypertension and atherosclerosis, respectively. Aortic tissue was collected from occidental (American and Australian) and Chinese populations from three geographic locations. Postmortem specimens were obtained from four fixed locations: ascending aorta (A), descending thoracic aorta (B), and abdominal aorta (suprarenal [C] and above the aortic bifurcation [D]). Histologic sections were used to measure aortic circumference, medial thickness, intimal thickness, and grade of atherosclerosis. Kidney sections were used to confirm the presence or absence of hypertension. A total of 302 cases (age range, 19 to 104 years; Male-to-female ration, 2:1) were studied: 112 Americans, 80 Australians, and 110 Chinese. Cases were divided into three age groups: 19 to 44; 45 to 64; and 65 years and older. The aortic circumference progressively decreased from sites A to D in all populations and age groups. The aortic circumference increased with age, and the increase was independent of the aortic location. When the populations were separated, however, the greater increase was at location A in the Chinese (P = .008) and locations D in the occidental (P = .13), a population contrast that was significant only in location A. Intimal thickness increased with advancing age and was maximal in the abdominal aorta. The population differences also were significant for intimal thickness and were significantly greater in the occidental population in B, C, and D locations, whereas for atherosclerosis significance was only seen in location D. Hypertension (as defined by the morphologic changes in the kidney) after adjusting for age, height, and weight resulted in no statistical significant effect on aortic circumference or on intimal thickness, but did show a significant increase in atherosclerosis score at locations B, C, and D. Also after adjusting for age, height, and weight, the Chinese had a significantly larger aortic circumference in location A compared with the occidental population, whereas in location D the occidentals with hypertension had a significantly larger circumference compared with Chinese, probably due to an interaction of atherosclerosis and hypertension. After similar adjustments, the medial thickness in locations A and C, the intimal thickness in B, C, and D, and atherosclerosis score in D were significantly greater in occidental than Chinese populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

Arterial compliance and wave reflection.

Left ventricular "afterload" is the wall stress developed during systole by the ejecting ventricle. For any given ventricular conformation, this is given by the time course of pressure change in the left ventricle during ejection, and is approximated by the pressure measured in the ascending aorta. For a given flow ejection from the left ventricle, pressure generated in the ascending aorta is determined by the ascending aortic impedance. Impedance in turn is dependent on three properties of the systemic circulation--resistance, compliance and wave reflection. In conventional studies of left ventricular load and hypertension, attention is usually focussed entirely on peripheral resistance. Recent studies have shown a poor relationship between left ventricular mass and peripheral resistance, but a better relationship with compliance and indices of wave reflection. Hence compliance (or its inverse, aortic stiffness) and wave reflection must be considered in evaluating hypertension (especially "systolic hypertension") and the effects of drugs on ventricular load. Under ideal circumstances, as seen in youth, aortic compliance is high and wave reflection late, with the consequence that aortic systolic pressure is low and pressure is boosted throughout early diastole. With progressive aortic degeneration as seen with aging and in hypertension, systolic pressure in increased both directly by decreased compliance, and indirectly by early return of wave reflection. The effect of early wave reflection is not apparent from recordings of brachial systolic or diastolic pressure, but can be inferred from indirectly recorded carotid pressure, or from contour of the peripheral pressure wave.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗
PubMed1990

Coupling between the left ventricle and arterial system in hypertension.

In youth and in health, a variety of factors combine to optimize coupling between the left ventricle and systemic circulation. In hypertension and with aging, optimal coupling is disturbed by increased arterial stiffness which increases systolic pressure through two different mechanisms. The first mechanism (reduced aortic compliance) is not directly affected by drugs, but the second (early wave reflection) is capable of modification by vasodilator therapy. Favourable effects of vasodilator agents may not be apparent when pressure is recorded conventionally in a peripheral artery but can be inferred from consideration of pressure wave contour. Recognition of these factors provides new strategies for dealing with hypertension and hypertensive heart failure in man.

Aging↗
PubMed1990

ECG evidence of limited myocardial infarction following coronary occlusion treated by early intravenous rt-PA infusion.

Serial 12-lead surface electrocardiograms (ECGs) were analysed in 110 patients with first evolving myocardial infarction entered in a double-blind placebo-controlled trial of intravenous rt-PA within 2.5 h (mean 1.9 +/- 0.5 (SD)) of pain onset. ECG analysis was performed by two 'blinded' analysts. QRS scoring (by the modified Selvester method) was used as an index of myocardial necrosis. Patient results were analysed according to infarct location. There was no difference between the two treatment groups in ST-segment elevation or QRS score at entry or up to 24 h after symptom onset. However from 24 h, QRS score was lower in patients with anterior infarction given rt-PA than in those given placebo: 5.4 +/- 2.8 vs 7.7 +/- 4.1 (P = 0.02) at 48 h; 4.7 +/- 3.2 vs 8.0 +/- 4.0 (P = 0.01) at 4-10 days; and 4.6 +/- 3.9 vs 7.5 +/- 3.9 (P = 0.01) at 21 days. For patients with inferior infarction, rt-PA treatment also resulted in a lower QRS score although this was not significantly different from the score of the placebo group (P = 0.07). Comparison of QRS scores with ejection fraction measured from the contrast ventriculogram taken at 21 days showed a moderate correlation (r = 0.46) in patients with anterior infarction but a poor correlation in patients with inferior infarction. These ECG results indicate that in evolving anterior myocardial infarction, there is limitation of infarct size from early rt-PA infusion.

Double-Blind Method↗
PubMed1990

Preventive strategies in management of acute myocardial infarction.

Recent studies on pathogenetic mechanisms, supplemented by findings in clinical trials point the way to a logical approach to acute evolving myocardial infarction. This is designed in the earliest stage to limit infarction through reduction in myocardial oxygen demands, improvement in collateral blood supply and dissolution of coronary thrombus, to prevent in a later stage coronary reocclusion through administration of antiplatelet agents, and then to prevent infarct expansion through reduction in ventricular wall tension throughout the period of repair. Application of such an approach holds the promise of reducing infarct size and all the complications of infarction, as well as short and long-term mortality. The approach is active and aggressive, and contrasts with the approach applied a decade ago, where infarction was accepted as inevitable and therapies were reserved for managing its complications.

Adrenergic beta-Antagonists↗
PubMed1990

Arterial stiffness, systolic blood pressure, and logical treatment of arterial hypertension.

Arterial stiffening is the principal cause of increasing systolic pressure with advancing years and in patients with arterial hypertension. It is associated with progressive arterial dilation and is due to degeneration of the arterial wall, probably as a consequence of repetitive cyclic stress; it increases systolic pressure directly by increasing amplitude of the pressure wave generated by a given flow impulse from the heart and indirectly by increasing wave velocity so that wave reflection from the periphery occurs earlier, augmenting pressure in late systole. The first mechanism affects pressure in both the central and peripheral arteries, the second predominantly in the central arteries. Change in brachial systolic pressure with age underestimates the rise in systolic pressure in the aorta and left ventricle. Arterial stiffness is reduced passively with reduction in arterial pressure. Drugs have little or no direct effect on arterial stiffness but can markedly reduce wave reflection. In patients with stiffened arteries, reduction in wave reflection decreases aortic systolic pressure augmentation. The decreased systolic pressure in central arteries brought about by this mechanism is not detected when systolic pressure is measured in a peripheral (brachial or radial) artery but can be inferred from change in contour of the pressure wave recorded in peripheral arteries.

Aging↗
PubMed1978

The role of long term beta-blockade after myocardial infarction: Paper 1.

The opinion is emerging that beta-blocking drugs have an important role in management of patients following acute myocardial infarction. Already beta-blocking drugs are accepted as the treatment of choice in hypertension and in angina pectoris--in the major risk factor and consequence respectively of coronary atherosclerosis, and both commonly recognized in patients who survive acute myocardial infarction. But beta-blocking drugs also may be of benefit in reducing the incidence and risk of subsequent infarction, and so may be of value for long term treatment of patients who have no symptoms whatever following acute infarction.

Acute Disease↗