Effect of geometrical characteristic and clot mechanical properties on coronary clot aspiration catheter performance

The coronary arteries supply blood and oxygen to the heart tissues. If this flow becomes blocked, the downstream part of heart muscles begins to die. This is called heart attack. The coronary arteries can get blocked by plaques which are the results of a slow process along the years called atherosclerosis. Although a coronary vessel is seldom completely blocked by a plaque, a complete blockage may happen if a clot lodges on the area. The plaque may also rupture and move and potentially cause a complete blockage. The coronary arteries can also become blocked by blood clot which is a result of hemostasis following tissue injury and abnormal vessel wall repair. If the coronary vessel is blocked with clot, several methods are available to tackle the issue: the coronary vessel could be treated with clot busting medicines or clot removing devices. In clot busting methods pharmacological methods are used to dissolve the clot. In the case of clot removing by means of devices, a very thin tube is guided toward the occluded vessel to mechanically remove the clot. Removal can occur according to different methods, including breaking down the clot and aspirating it. The most reliable method is based on the usage of coronary aspiration catheters. The aspiration catheters remove the clot only through the aspiration force. This method is the most preferred one as it has minimal clinical drawbacks and high effect. Although the results of aspiration catheter deployment have been investigated in a number of clinical trial studies, the quantitative prediction and comparison of catheter performances is also important in terms of aspiration ability. The main aim of the current study is to address this issue. More precisely, the purpose is to find out how an aspiration catheter aspirates a clot when used in different scenarios. In fact a wide range of aspiration catheters are available for the percutaneous coronary intervention purposes. These catheters mainly differ in their tip geometry and design. The geometrical differences include size, tip shape, lumen diameter and hole design. The study of catheter geometrical parameters is combined with that of clot mechanical properties, which is a very important factor for the success of percutaneous coronary intervention for clot removal. The adopted workflow starts with the study of rheology of incipient clots and clots with initial resting while exposed to a wide range of preconditions. Then the clot rheological characteristics are used to numerically model the clot aspiration into a standard catheter in order to investigate the clot displacement and the time needed for its aspiration. The numerical results are then compared to understand the role of each parameter on coronary aspiration catheter performance and final outcome. Eventually the behavior of the whole system catheter is studied experimentally with regard to different designs of a commercial manual aspiration catheter (Diver CE, Invatec S.r.l., Roncadelle, BS, Italy).