Contractility of the left ventricle of the human heart noninvasive measurement in each cardiac cycle
Khaiutin, V.M.; Lukoshkova, E.V.; Ermishkin, V.V.; Sonina, R.S.
Kardiologiia 50(4): 38-44
2010
ISSN/ISBN: 0022-9040 PMID: 20459420 Document Number: 640410
History of development of the method of measurement of duration of the preejection (DPE) period - characteristic of left ventricular (LV) contractility is presented. On the basis of physiological prerequisites a novel computerized method of DPE measurement in each consecutive cardiocycle has been created. Distinct features of this method are: 1) principle of measurement - tetrapolar impedancemetry, with signal electrodes located along projection of the ascending aorta, one in the center of presternum, second - 5 cm caudally; 2) starting point for DPE counting - the point on ascending portion of R wave of electrocardiogram at which the first derivative of ECG signal reaches maximum, stopping point - the point of maximum of the second derivative of the primary impedance signal on the ascending front of its pulse wave. The method has been tested on healthy people for 10 functional tests. The results are presented characterizing dynamic peculiarities of changes of LV contractility during veloergometer exercise test with staderly increasing work load and reflecting development of positive inotropic action of sympathetic nervous system. Special characteristics of this action: small concealed period, preservation of achieved elevated level during lowering of work load (before its switching off) and subsequent slow (compared with chronotropic effect) diminution, as well as turning on at low loads.