Cardiac-coronary interactions in humans: Mechanistic insights from wave intensity analysis

Intracoronary pressure and flow-velocity signals reflect the interaction between cardiac mechanics and coronary hemodynamics. In this thesis we explored the origin of the time-varying characteristics of these signals in relation to cardiac mechanics in particular in disease, as result of treatment and interventions. Coronary hemodynamic signals were obtained in patients with coronary or aortic valve diseases with a dual-sensor guidewire equipped with both a pressure and a flow-velocity sensor. Based on these signals, wave intensity analysis was performed allowing separating, in terms of waves travelling on the vessel wall, the components responsible for the measured intracoronary signals: forward waves coming from the aorta and backward waves coming from the microcirculation. The magnitude of each wave is the consequence of the force by which it is generated and the parameters that cause its attenuation. All waves are generated by cardiac contraction and relaxation so they are strongly related to parameters of cardiac mechanics such as LVdP/dt. The forward waves are strongly related to aortic pressure waveform while the energy of the coronary backward waves is modulated by the intramyocardial volume. Intracoronary pressure and flow-velocity waveforms are the results of a complicated interaction of different factors. Characterizing these signals in terms of wave intensity analysis allows identifying the separate parameters responsible for the waveforms during the cardiac cycle. This technique therefore not only provides an important tool to understand the physiology behind the intracoronary signals but, in case of disease, could also open new possibilities for improvements in clinical diagnosis and treatment