Lars‐Göran Ekelund

Measurement of Cardiac Output by Impedance Cardiography in Patients with Myocardial Infarction: Comparative Evaluation of Impedance and Dye Dilution Methods

The cardiac output was measured simultaneously by the impedance cardiography and dye dilution methods in 10 patients with acute myocardial infarction 2-3 weeks after admission to the Coronary Care Unit. The impedance cardiac output was on the average 9.7% higher than the dye dilution cardiac output. The reproducibility of impedance cardiac output 4.1%, compared with 5.1% for the dye dilution method. The study showed a satisfactory reliability of impedance in predicting the relative changed of cardiac output in response to tilting from the supine to the 30 degrees head-up position, to a 10 degrees head-down position, and to the intravenous administration of propranolol.

Metabolic and cardio-vascular effects of serotonin☆

Abstract Serotonin was given intravenously as a constant infusion of 2 to 4 μg per kg b.w. per min during 20-minute periods to four male volunteers. The levels of free fatty acids (FFA) and glycerol in arterial blood plasma increased. The blood glucose concentration was unchanged. The oxygen consumption increased. Repeated serotonin infusion in two of the subjects, after administration of a serotonin “antagonist”, cyproheptadin or methysergid, caused greater increases in the levels of FFA and glycerol and in oxygen consumption. The pulse rate increased in all subjects without significant change in blood pressure. Serotonin was also infused into three dogs during 30 minutes in a dose of 8 μg/kg/min. The levels of FFA and glycerol in blood plasma increased in two of them. The heart rate increased and the blood pressure decreased. The addition of serotonin to human as well as rat adipose tissue incubated in vitro stimulated the release of glycerol.

Significance of primary T wave aberrations in the electrocardiogram of asymptomatic young men, III. Systolic time intervals and autonomic tone

Fifteen healthy male subjects, aged 18-19 years, with primary T wave aberrations consisting mainly of notches in the T wave without concomitant ST depression (group T) were compared to twenty-six controls of the same age with normal electrocardiograms. The T wave aberrations were eliminated by beta-adrenergic blockade in thirteen subjects in group T. Physical exercise decreased all the T wave aberrations. Group T was on average shorter and had signs of higher sympathetic tone, as shown by a higher heart rate and systolic blood pressure, than the controls and the parasympathetic tone was lower, as indicated by a higher heart rate during beta-adrenergic blockade. No significant differences in physical work capacity and heart volumes were found. Measurement of systolic time intervals suggested increased sympathetic influence on the heart and no signs of cardiac impairment. Thus the majority of subjects with aberrant T waves had changes in the autonomic tone and no signs of functional impairment of the heart.

Significance of Primary T Wave Aberrations in the Electrocardiogram of Asymptomatic Young Men

The electrocardiogram (ECG) at rest and during orthostasis and exercise in 51 healthy men 18-19 years of age without history or symptoms of heart disease, but with T wave aberrations in the ECG (group T) were compared to the normal ECGs of 112 controls of the same age. These aberrations (which literature suggests to be due to organic heart disease) consisted of either a notch in the T wave, especially in the midprecordial leads, that sometimes became inverted, or a low T wave without concomitant ST depression. The T wave aberrations at rest in group T were similar to what 25% of the controls evidenced during orthostasis (group B). Both group T and group B had signs of increased sympathetic tone at rest with a higher heart rate and systolic blood pressure than did the subjects with normal ECG both at rest and during orthostasis. These T wave aberrations disappeared for the majority during exercise. Both group T and group B had prolonged QTc intervals. Group T had increased R wave amplitudes which did not correlate to the severity of the T wave aberration or to systolic blood pressure. Our opinion is that primary T wave aberrations in the majority of these young men were because of increased sympathetic tone.