Comparison of cardiac time intervals between echocardiography and impedance cardiography at various heart rates

Abstract

The non-invasively measured initial systolic time interval (ISTI) reflects a time difference between the electrical and pumping activity of the heart and depends on cardiac preload, afterload, autonomic nervous control and training level. However, the duration of the ISTI has not yet been compared to other time markers of the heart cycle. The present study gauges the duration of the ISTI by comparing the end point of this interval, the C-point, with heart cycle markers obtained by echocardiography. The heart rate of 16 healthy subjects was varied by means of an exercise stimulus. It was found that the C-point, and therefore the end point of ISTI, occurred around the moment of the maximum diameter of the aortic arch in all subjects and at all heart rates. However, while the time difference between the opening of the aortic valves and the maximum diameter of the aortic arch decreased significantly with decreasing RR-interval, the time difference with respect to the moment of the C-point remained constant within the subjects. This means that the shortening of the ISTI with increasing heart rate in response to an exercise stimulus was caused by a shortening of the pre-ejection period (PEP). It is concluded that the ISTI can be used as a non-invasive parameter indicating the time difference between the electrical and mechanical pumping activity of the heart, both inside and outside the clinic.

Do depressive symptoms “blunt” effort? An analysis of cardiac engagement and withdrawal for an increasingly difficult task

“…The cardiac pre-ejection period (PEP)—the time (in ms) between the ECG Q point (the onset of ventricular depolarization; Berntson et al, 2004) and the dZ/dt B point (the opening of the aortic valve and start of left ventricular ejection; Lozano et al, 2007)—is widely used in effort research (Richter, 2012). As a secondary sympathetic outcome, we also computed the RZ interval: the time (in ms) between the ECG R point (the point of peak electrical activity) and the dZ/dt Z point (the dZ/dt peak and point of maximal diameter of the aortic arch; van Eijnatten, van Rijssel, Peters, Verdaasdonk, & Meijer, 2014). Also known as the initial systolic time interval (ISTI; Meijer, Boesveldt, Elbertse, & Berendse, 2008), RZ is increasingly popular as a measure of contractility.…”

Assessment of cardiac time intervals by wavelet transform of the impedance cardiogram

“…The absolute shortening of ISTI for the patient with hypertension can be attributed to compensatory reaction and increased myocardial contractility. Also we have observed the shortening of the ISTI with increasing heart rate in response to an exercise stimulus in the same spirit as in [10]. It is interesting that ISTI has different slopes for healthy subjects (IST I ∝ 0.14RR) and the patient with hypertension (IST I ∝ 0.1RR).…”

“…The objective of this work is a demonstration of the wavelet transform for processing and interpretation of the impedance cardiogram waveforms and an investigation the possibilities of this approach to determine the parameters of the SV, in particular LVET. Also we measured initial systolic time interval (ISTI) -delay between electrical and mechanical pumping activities of the heart [10]. We note that ISTI is not particularly different from the electro-mechanical delay.…”

Psychopathology, everyday behaviors, and autonomic activity in daily life: An ambulatory impedance cardiography study of depression, anxiety, and hypomanic traits

“…PEP is the time (in ms) between the ECG Q point (Berntson et al, 2004) and the dZ/dt B point (Lozano et al, 2007). The RZ interval is the time (in ms) between the ECG R point and the dZ/dt Z point (Meijer et al, 2008; van Eijnatten et al, 2014). The points were based on ensemble averages (Kelsey et al, 1998).…”