Biomedical subjects

R W Giles

Publications and source records attributed to R W Giles.

23 records · Page 2Linked to original sources

PubMed1981

Multigated equilibrium radionuclide angiocardiography: improved detection of left ventricular wall motion abnormalities and aneurysms by the addition of the left lateral view.

The usefulness of adding the left lateral (LLAT) view to the standard anterior and left anterior oblique views in multigated equilibrium radionuclide angiocardiography was assessed in 50 patients. Contrast ventriculography was used as the standard. Receiver operating characteristic (ROC) curve analysis was used to assess results. Recognition of inferior wall motion abnormality and left ventricular aneurysms was improved significantly by the addition of the LLAT view. Sensitivity was improved for inferior wall motion abnormality and for aneurysms; there was no loss of specificity. There was no improvement in recognition of anterior wall and apical regional abnormalities in the absence of aneurysms.

Adult↗

PubMed1977

Reactive hyperaemia in the dog heart: evidence for a myogenic contribution.

Temporary restriction of arterial inflow after release of eight second coronary artery occlusions greatly reduced reactive hyperaemia but prolonged its duration. Early repayment of the flow debt before restriction did not alter these changes. Despite reduced hyperaemia, there was evidence of subendocardial ischaemia during restriction. Yet occlusions of only one and two cardiac cycles produced marked hyperaemia without evidence of post-release subendocardial ischaemia. All these changes were associated with alterations in peripheral coronary artery pressure consistent with myogenic responses contributing to reactive hyperaemia.

Animals↗

PubMed1977

Reactive hyperaemia in the dog heart: inter-relations between adenosine, ATP, and aminophylline and the effect of indomethacin.

Intracoronary adenosine, ATP, and the release of an 8 second occlusion increased coronary blood flow (CBF) to a similar extent. Aminophylline decreased the CBF response to adenosine by 80% and that to an 8 s occlusion by 20% but did not change the CBF response to ATP. Indomethacin had no effect on CBF. The results suggest that the increase in CBF after brief occlusions is not mediated in a major way by adenosine or prostaglandins.

Adenosine↗

PubMed1977

Histamine receptors in the coronary circulation of the dog. Effects of mepyramine and metiamide on responses to histamine infusions.

The effect of histamine on coronary blood flow (CBF) was studied in anaesthetized grayhounds. CBF and systemic blood pressure were measured using electromagnetic flow transducers and catheters in the aorta during infusions of drugs into the left circumflex coronary artery. Histamine infusions (5, 10, and 20 microng/min) produced dose-related increases in CBF without changing heart rate or blood pressure. Metiamide (100 microng/min) given simultaneously produced a parallel displacement of the histamine dose-response curve to the right (P less than 0.05) with a dose ratio of 2. Mepyramine (100 microng/min) produced a larger parallel displacement of the dose-response curve (dose ratio = 4). Together, metiamide and mepyramine greatly reduced the histamine response (dose ratio = 16), showing that the metiamide blockade is augmented in the presence of mepyramine. Similarly, mepyramine blockade is augmented in the presence of metiamide. The increase in CBF produced by histamine infusion (20 microng/min) was similar to the peak flow response of reactive hyperemia following 8-second occlusions. However, mepyramine and metiamide together had no effect on the peak flow response, duration, or total repayment of flow debt in reactive hyperemia. These results show that histamine-induced coronary vasodilation is mediated by both H1 and H2 receptors. However, the vasodilation of reactive hyperemia after brief coronary artery occlusions does not appear to involve histamine.

Animals↗

PubMed1975

Effects of catecholamines on the coronary circulation in the Langendorff-type transplanted dog heart.

Intracoronary administration of isoprenaline, adrenaline, and the noradrenaline in the Langendorff-type transplanted dog heart transiently decreased coronary blood flow measured from the inflow vessel; flow then increased. The reduction in coronary flow coincided with increased myocardial contractility and was prevented by keeping the left ventricle empty. Propranolol prevented changes in flow and contractility. It is concluded that positive inotropic changes result in the ejection of accumulated Thesbesian flow from the ventricle and affect coronary flow measurements and that the interpretation of flow changes requires a steady state.

Animals↗