An experimental assessment of catheter trackability forces with tortuosity parameters along patient-specific coronary phantoms

Coronary artery disease is one of the leading causes of cardiovascular deaths worldwide. Approximately 70% of patients requiring coronary revascularisation receive endovascular stents. The endovascular procedure is the preferred option due to its minimally invasive nature when compared to open heart surgery. Stent delivery is paramount for the success of the endovascular procedure. Catheter delivery forces within tortuous blood vessels can produce vasoconstriction and injury, resulting in reactive intimal proliferation or distal embolisation associated with end-organ ischaemia and infarction. Trackability is evaluated by most medical device companies for further development of their delivery systems. Relevant device design attributes must be tested in settings which simulate aspects of the intended use conditions, such as vessel geometry and compliance. Various tortuosity parameters are used to facilitate endovascular intervention planning. This study assessed the significance and correlation between the trackability forces for a coronary stent system with various geometrical parameters based on patient-specific geometries. A motorised delivery system delivered a commercially available coronary stent system and monitored the trackability forces along three phantom patient-specific thin-walled, compliant coronary vessels supported by a cardiac phantom model. The maximum trackability forces, curvature and torsion values ranged from 0.31 to 0.87 N, 0.06 to 0.22 mm^'1 and '11.1 to 5.8 mm^'1, respectively. The trackability forces were significantly different between all vessels (p < 0.002), while the tortuosity parameters were not significantly different (p > 0.05). A new tortuosity parameter-coined tracking curvature which considers the lumen radius as well as the curvature along the centreline was statistically different (p < 0.002) for all vessels and correlated with the trackability forces. There was a strong correlation between the cumulative trackability force and the cumulative tracking curvature. Tracking curvature could be used as a predictive clinical tool to aid stent delivery to the vicinity of the lesion.