Abstract
In intracardiac impedance, electrical bio-impedance is measured inside the heart. This signal is known to reflect the volume of blood passing in and out of the ventricles. In transthoracic impedance the measurement current and voltage sensing is connected on the subject’s chest. In this thesis, the intracardiac impedance is studied in general, and in the filling phase (diastole) in particular.
The diastolic intracardiac impedance displays a consistent slope change (notch). The notch in the present thesis has similar features as the noninvasive transthoracic impedance O-wave reported earlier. The notch occurrence was found to be well comparable with results in work with O-wave. The notch was found closely after early rapid ventricular filling but before ventricular filling caused by atrial contraction and it is concluded that the notch is not caused by atrial contraction. The notch is most likely caused by cardiac wall movements in rapid ventricular filling.
The observations in this thesis are made in two different data sets; in animals and in humans and with different types of intracardiac leads. The lead implantations were performed by several different physicians. With the consistent results from these two studies at hand, this licentiate thesis concludes that the diastolic intracardiac impedance notch is a characteristic of intracardiac impedance, that the notch is the intracardiac equivalent of the non-invasive transthoracic impedance O-wave and that it is a sensed physiological cardiac parameter of diastole. Since the present data is measured intracardically it can be concluded that the non-invasive O-wave in fact is caused by cardiac movements.
