Establishment of an experimental animal model for transcatheter aortic valve replacement

AIM:To establish an experimental animal model of transcatheter aortic valve replacement（TAVR） and to determine the optimal projecting position for aortic root angiography.METHODS:Fifteen healthy adult sheep were selected.From the lower 1/3 neck to the suprasternal fossa,the diameter of the aortic annulus and carotid artery were measured by echocardiography and vascular ultrasound,respectively.Common carotid artery was then dissected and measured under direct vision.Left ventriculography via the same carotid artery using a pigtail catheter was performed and the best projecting position for demonstrating the aortic root was evaluated.Both 20 French（F） and 24F catheter delivery sheaths were inserted through the dissected carotid artery.The effective orifice area（EOA）,reflux percentage,heart rate,systolic aortic pressure（SAP）,diastolic aortic pressure（DAP）,mean aortic pressure（MAP）,left ventricular systolic pressure（LVSP）,and left ventricular end diastolic pressure（LVEDP） were evaluated pre-and postoperatively by transthoracic echocardiography（TTE） and cardiac catheter technology.RESULTS:Echocardiography showed that the diameter of systolic aortic annulus and diastolic aortic annulus at suprasternal fossa was（24.98±2.41） mm and（19.82±2.14） mm,and vascular ultrasound showed that the diameter of carotid artery at the lower 1/3 neck and thoracic entrance was（9.16±0.84） mm and（5.61±0.50） mm,respectively.By direct vision,diameter of the carotid artery was（5.90±0.64） mm.The 20F catheter delivery sheaths were easily inserted through the carotid arteries of all sheep and the 24F catheter delivery sheaths were successfully inserted through the carotid arteries of 13 sheep.The ostia of left and right coronary arteries and aortic root were well demonstrated in the position of right anterior oblique 2.5°±3° plus cranial 7.1°±6°.No significant difference was observed between pre-and postoperative measurements of EOA,reflux percentage,heart rate,ASP,DAP,MAP,LVSP,and LVEDP.CONCLUSION:Transcatheter aortic valve prosthesis is implanted via the carotid artery of adult sheep by retrograde approach.Using angiography,the optimal projecting position to visualize the aortic root and coronary ostia is right anterior oblique 2.5°±3 plus cranial 7.1°±6°.This model meets the requirements of animal study for the TAVR system.