[Pre-ejection period as a cardiac cotractility index: noninvasive beat-by-beat evaluation in the human study].

Beat-by-beat evaluation of left ventricular contractility provides and insight to the current dynamics of cardiac control. In non-invasive studies, pre-ejection period is conventionally used as an index of contractility. Pulse waves of electrical impedance (deltaZ) reflect the systolic dilations of the aorta segment confined between the properly placed signal electrodes. The relation of B-wave in the differentiated signal dZ/dt to the dalation of the aortic root prior to the start of ejection is discussed. The previous findings and our own experience indicate that the conventional method of identification of the end of the pre-ejection period by the B-point is not suitable for its reliable determination in each cardiac cycle. Instead of this, we defined the start of election by the maximum of the d(2)Z/dt2 signal associated with maximum acceleration of the ascending aorta dilation during the early ejection phase. It can be reliably found beat-by-beat. The proposed technique was successfully aplied for monitoring of fine dynamics of pre-ejection period changes during Valsalva maneuver, as well as in active and passive orthostatic tests.