Changes of decartograms under gravitational acceleration and microgravity.

The Decarto technique was used to study the orthogonal ECGs recorded in 23 subjects during parabolic flights (44 records). A parameter of the instantaneous decartograms, namely the activation area (AA), which is the total area of the depolarization front projection on the image sphere, was analyzed. We compared the values of AA during the periods of horizontal flight, upward parts of all parabolas, and the initial 10 s of microgravity of all parabolas. According to the characteristics of the vectorcardiograms and AA, all subjects were subdivided into 3 groups: with increased electric activity of the right ventricle (I), the left ventricle (II) and both ventricles (III). Changes of AA with change of gravitational levels in these groups showed some differences. In groups I and II, the AA of the initial part of the QRS complex increased during microgravity and decreased during hypergravity. In group III it decreased during microgravity and changed variously during hypergravity. The AA of the middle part of the QRS complex decreased during microgravity and increased during hypergravity, and these changes were more pronounced in group III. The changes of AA in groups I and II may be explained by the Brody effect. In group III, AA seems to be influenced by some additional factors, possibly by changes in the intramyocardial or intraventricular blood volume. The AA of the last part of the QRS complex increased during microgravity and decreased during hypergravity in all groups. This may be explained by an effect of mutual neutralization of depolarization fronts related to the changes of the QRS duration.(Fig. 3, Ref. 4)

Non-invasive ultrasound detection of endothelial dysfunction.

With high resolution ultrasound we assessed endothelial function in subjects at risk of atherosclerosis. We used ACUSON 128XP/10 system with 7.0 MHz linear array transducer. Three groups of patients (pts) were studied: 12 patients with essential hypertension, ten patients with 2A familial hyperholesterolamia and ten controls without vascular risk factors. We measured the diameter of brachial artery at rest, during reactive hyperaemia (with increased flow causing endothelium-dependent dilation), and after sublingual 0.01 mg nitroglycerin (causing endothelium-independent dilation). Flow-mediated dilation is not impaired in essential hypertension (9. 4%) compared with controls (9.5%) and impaired in patients with familial hyperholesterolaemia (3.0%). NTG-induced dilation is not impaired in familial hyperholesterolaemia (16.6%) and essential hypertension (14.5%) compared with controls (20.5%). The effect of hypolipidaemic influence (probucol and plasmapheresis) was assessed in a separate study. These results demonstrate the capability of ultrasound in detection of endothelial dysfunction, and suggest that endothelial dysfunction in patients with familial hyperholesterolaemia is one of the risk factors for atherosclerosis. The parameters of endothelial function may be used as markers of hypolipidemic influence on patients with hyperholesterolaemia.