Fluid mechanics of thermodilution in coronary arteries

Cardiovascular disease is one of the main causes of death in the world and among various cardiovascular diseases, the coronary artery disease is considered to be the leading cause of death. Atherosclerosis is the primary cause of coronary artery disease. Different diagnostic methods have been developed for the assessment of coronary artery function. Coronary Thermodilution is one of the most recent methods used to find blood flow, temperature and assess resistance. A diagnostic coronary guidewire with a pressure and temperature sensor is used to measure temperature and pressure of blood simultaneously. For a continuous temperature signal, the rapid reduction in temperature and afterwards recovery in seconds creates a temperature curve which is displayed on the haemodynamic monitoring device. The objectives of this study were to evaluate the thermodilution waveforms in order to understand microvascular disease of the heart. To investigate these thermodilution curves, a Matlab program was written to assess and to identify the key features of the thermodilution waveforms and different patterns of thermodilution curves were found. In order to calculate the origin of the features of the double peaks and other thermodilution curves, a simplified computational model of tube with catheter was implemented in Fluent. We observed the temperature curves similar to the thermodilution curves when we took the measurement at the centre of the coronary artery and did not see any pulsatility due to the probe lies within the central axis and lies within the region of cold fluid and may be diffusion is too slow to absorb heat from the surroundings. Double peaks are found if the probe is off-axis. Stenosis is placed inside the coronary artery and the calculations were performed off-axis which resulted in the different shapes as we observed in the actual thermodilution data. Misalignment of the catheter may result in the errors of thermodilution data which may affect the health care cost