Methods to assess the coronary circulation by guidewire-mounted sensors

Methods to assess the coronary circulation by guidewire-mounted sensors SummaryDisease in the coronary circulation can cause local blood flow impediment anywhere in the vascular system of the heart, from the larger epicardial vessels to the capillaries in the microcirculation.The disease may lead to severely increased resistance to blood flow resulting in myocardial ischemia.In the catheterization laboratory, the initial approach to investigate coronary disease is to perform coronary angiography: by injecting contrast medium the epicardial coronary arteries are made visible on X-ray film.However, in this way only a two-dimensional, qualitative assessment is made, easily over-or underestimating the physiological significance of disease.To obtain direct knowledge on the resistance to flow, quantitative information regarding blood pressure and flow is needed.Pressure and flow can be measured during catheterization by means of sensor-tipped guidewires introduced into the arterial system through the groin.From the practical point of view, it is desirable to have one single sensor-tipped wire equipped to measure both pressure and flow.The main aim of the study described in this thesis was to develop a method for simultaneous assessment of coronary pressure and flow by a single guidewire, the pressure-temperature sensor-tipped PressureWire (Radi Medical Systems, Uppsala, Sweden).Hereto well-controlled experimental evaluation conditions were mandatory.Practically, in-vivo experiments are often limited in controlling relevant parameters and moreover, from the ethical point of view, alternatives for evaluation in animal models or patients are desirable.Therefore a second focus of the work described in this thesis was to design and use an in-vitro model of the coronary circulation for well-controlled evaluation circumstances.The design of the in-vitro model was based on physiologically representative functional elements for the relevant components of the circulation, both regarding Left Main Aorta Coronary