Cardiovascular research
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Cardiovascular research · Mar 1990
Comparative StudyNon-invasive continuous finger blood pressure measurement during orthostatic stress compared to intra-arterial pressure.
The aim of the study was to evaluate whether invasive blood pressure responses to orthostatic stress can be replaced by non-invasive continuous finger blood pressure responses. DESIGN - Intrabrachial and Finapres blood pressures were simultaneously measured during passive head up tilt and during active standing from the supine or sitting position in healthy volunteers. ⋯ For the assessment of the continuous blood pressure responses to orthostatic stress similar information can be obtained with non-invasive Finapres blood pressure recordings as with invasive recordings.
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Cardiovascular research · Jan 1990
Insulin and beta adrenergic effects during endotoxin shock: in vivo myocardial interactions.
STUDY OBJECTIVE - Catecholamine concentrations are raised during endotoxin shock and may be responsible for myocardial insulin resistance in such a condition. The purpose of the investigation was to examine the effect of insulin on myocardial contractility and glucose uptake in the presence of beta adrenergic blockade during endotoxin shock. DESIGN - Endotoxin shock was obtained in dogs by giving S Typhimurium endotoxin intravenously (1 mg.kg-1) and the cardiac responses to insulin were determined under hyperinsulinaemic (4 U.min-1) euglycaemic clamp conditions during continuous beta adrenergic blockade (propranolol 150 micrograms.kg-1 + 5 micrograms.kg-1.min-1). ⋯ In controls, insulin increased myocardial performance; in shock this response was attenuated. CONCLUSIONS - The findings confirm that the myocardium becomes less responsive to the glucose uptake stimulating and positive inotropic effects of insulin during endotoxin shock. The data show that beta adrenergic activity is responsible for the increased contractile state of the heart during acute endotoxin shock, but is not the cause of the observed insulin resistant state.
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Cardiovascular research · Jul 1989
Mexiletine-quinidine in isolated hearts: an interaction involving the sodium channel.
Combination therapy with mexiletine and quinidine has been shown to be more effective than either monotherapy in treating patients with ventricular tachycardia. This enhanced efficacy was associated with prolongation of ventricular refractoriness and conduction time in the infarct zone. As sodium channel activity is a determinant of both conduction time and refractoriness we formed the hypothesis that the mexiletine-quinidine interaction was due at least in part to interactions involving the sodium channel. ⋯ The combination of similarly low concentrations of tetrodotoxin and quinidine also produced enhanced anti-arrhythmic efficacy and enhanced prolongation of ventricular refractoriness and conduction which mimicked the effect of mexiletine and quinidine in combination. In contrast, the combination of mexiletine and tetrodotoxin did not produce enhanced anti-arrhythmic and electrophysiological activity. Since tetrodotoxin is a highly specific sodium channel blocker, these data suggest that the enhanced antiarrhythmic activity of mexiletine-quinidine combination therapy involves, at least in part, blockade of the cardiac sodium channel.
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Cardiovascular research · Apr 1989
End tidal carbon dioxide as an haemodynamic determinant of cardiopulmonary resuscitation in the rat.
End tidal PCO2 (PETCO2) has been found to be a good prognostic indicator of successful resuscitation from cardiac arrest. To explore the value of this measurement further, we carried out a series of experiments during cardiac arrest and closed chest resuscitation in 14 mechanically ventilated Sprague-Dawley rats. Ventricular fibrillation (VF) was induced by a 10 mA current delivered to the right ventricular endocardium. ⋯ The PETCO2 correlated with the mean aortic (r = 0.71) and coronary perfusion pressure (r = 0.80) generated during precordial compression. In corroboration of previously reported observations on pigs, dogs, and human patients, PETCO2 served as a non-invasive monitor of the effectiveness of precordial compression for maintaining coronary perfusion and therefore cardiac viability during CPR. The PETCO2 was also useful in that it promptly signalled restoration of spontaneous circulation.
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Cardiovascular research · Aug 1987
ReviewClinical and research implications of new concepts in the assessment of cardiac pumping performance in heart failure.
Every cardiac pump has its own maximum performance, which denotes its pumping capability. The difference between the performance in the resting state and that at maximum is called pumping reserve. ⋯ Cardiac pumping capability is predictive of the ultimate prognosis of patients in severe heart failure whereas pumping reserve is a major determinant of exercise capacity. The therapeutic efficacy of cardiotonic drugs used in the treatment of ambulant heart failure patients should be evaluated with reference to the way they alter the relation between cardiac pumping reserve and exercise capacity.