Myocardial hibernation identified by hyperbaric oxygen treatment and echocardiography in postinfarction patients: comparison with exercise thallium scintigraphy.

To evaluate the potential for hyperbaric oxygen (HBO) to produce transient improvement in function in areas of myocardium ischemic at rest (hibernating myocardium), 24 patients were studied within 1 week of acute myocardial infarction. Results were compared with single-photon emission computed tomography (SPECT) thallium-201 exercise scintigraphy. Echocardiography demonstrated improved contraction following HBO in 20 of 62 damaged left ventricular segments in 12 of 24 patients. Thirteen of the 28 segments and 9 of the 14 patients showing reversible ischemia on SPECT imaging showed improvement with HBO. There were eight segments with apparently normal resting contraction that showed a reversible thallium defect. Of 42 segments with fixed contraction abnormalities following HBO, eight had reversible thallium defects, four had normal thallium kinetics, and 30 had fixed thallium defects. Thus hyperbaric oxygen can demonstrate improvement in function in some segments of left ventricle after infarction. There is some overlap with viability as determined by thallium studies, but the two techniques may be complementary in describing myocardial ischemia.

Chlamydial endocarditis.

Echocardiographic diagnosis of a case of endocarditis, subsequently proven to be due to a chlamydial organism, is described. Early echocardiographic diagnosis guided initial medical management and directed urgent surgical intervention when the patient deteriorated. Reported cases of chlamydial endocarditis are reviewed.

A comparison of intravenous and intracoronary streptokinase in acute myocardial infarction.

A randomised study of intravenous and intracoronary streptokinase therapy was carried out in 20 subjects with acute myocardial infarction and angiographically confirmed complete obstruction of the associated coronary artery. Two dose levels of therapy were used. Although more recanalisations occurred with intracoronary than intravenous therapy at the low dose levels, overall there was not a significant difference between the two groups; one million IU intravenously over 20 minutes recanalised four of five arteries. While seven of nine recanalisations with intracoronary therapy occurred within an hour, only two of five with intravenous therapy did so. Hence prolonged angiographic observation is necessary to document recanalisation with intravenous therapy adequately. Nevertheless, the time disadvantage of large dose intravenous therapy is not great and it may yet prove as effective as, and more practical than, intracoronary therapy.

Inosine as a selective inotropic agent on ischaemic myocardium?

Intravenous infusion of inosine (15 mg.kg-1.min-1) to the open-chested pig resulted in hypotension, coronary vasodilatation and slightly increased myocardial contractility. Following coronary occlusion, the action of inosine to increase myocardial contractility was apparently selective. Regional myocardial performance of ischaemic myocardium was increased significantly relative to nonischaemic. The selectivity of inotropic action was not mimicked by glucose-insulin-potassium. It is concluded that the selectivity is multifactoral and that the inotropic, vasodilatory and metabolic actions of the nucleoside contribute to the apparent selectivity.

Monophasic action potentials, electrocardiograms and mechanical performance in normal and ischaemic epicardial segments of the pig ventricle in situ.

Few studies report simultaneous electrical and mechanical recordings from the epicardium of intact beating hearts in situ during ischaemia. We use suction to apply transducers and electrodes to areas of the epicardium. This interferes little with its behaviour and allows: i) free mobility over the surface; ii) simultaneous tridirectional length changes to be recorded and summed for an overall impression of mechanical behaviour, iii) detection of changes in direction of movement; iv) simultaneous recordings of monophasic action potential and epicardial ECG. During ischaemia we can detect impaired contraction with dyskinesis and a change in direction of epicardial forces. The action potential duration shortens and we have noted impaired conduction, inexitability and recordings consistent with re-entry leading to ventricular fibrillation.