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Division of Cardiothoracic Surgery, UCSF Medical Center, San Francisco VA Medical Center, 350 Parnassus Ave, Suite 150, Box 0118, San Francisco, CA 94143
(Email: tsenge{at}surgery.ucsf.edu; matthews-rurakp{at}surgery.ucsf.edu; guys{at}surgery.ucsf.edu).
The advent of 64-slice computed tomographic scanners with three-dimensional (3-D) angiographic reconstruction has made a significant impact on the vascular surgical discipline, most notably to endovascular stent graft repairs. These technological advances also enhance preoperative cardiac surgical planning, particularly in the reoperative setting. Determination of the distance of patent left internal mammary arteries or saphenous vein grafts to the sternum, along with their route to the myocardium, is an excellent example of how rendering patient anatomy in 3-D space facilitates safer sternal re-entry [1]. Avoidance of other critical structures, such as the innominate vein, aorta, and right ventricle, as well as evaluation of adequate aortic cannulation and cross-clamp sites are additional advantages [2]. The authors [3] have taken 3-D visualization one step further, bringing physical models right into the operative setting. Stereolithographic prototyping allows surgeons to freely and easily manipulate the model, an impressive advance over two-dimensional axial imaging.
Ultimately, the time and cost of stereolithographic prototyping models must be weighed against their usefulness as a tool in the operating room. However, the authors' work has intriguing implications for a wide range of other surgical applications. Fabrication of a lifelike model of patient anatomy would be particularly useful when evaluating the option of minimally invasive surgery. For instance, reoperative aortic valve replacement as described here may be approached with an upper mini-sternotomy or parasternal approach based on left internal mammary artery location. The ideal placement of the aortotomy in relation to patent grafts could be planned in detail given the availability of a physical 3-D reconstruction. Similarly, lower mini-sternotomy or right thoracotomy approaches may be favored for mitral surgery. Pinpointing the location of a patent graft may influence the surgeon's choice of atrial incision. Finally, such models would enhance robotic left internal mammary artery harvest and minimally invasive direct coronary artery bypass by determining appropriate locations for the minimally invasive direct coronary artery bypass incision and risk of intramyocardial left anterior descending coronary artery [4]. Overall, choice of incisions and surgical exposure of valves and coronaries may be significantly altered with careful preoperative 3-D assessment using rapid prototype models.
Visualization of high-risk anatomy with significant calcification may result in hybrid procedures being entertained. Future procedures, particularly determinations between percutaneous and apical approaches to transcatheter aortic valves, may be heavily influenced by the information obtained through 3-D models. A detailed prototype of the patient anatomy would be able to determine proximity of the left ventricular apex to the chest wall, degree of arch calcification and disease, and the size and quality of iliac and femoral access vessels. Finally, stereolithographic prototyping has its role in resident education. Given the trend toward percutaneous and minimally invasive procedures with limited visibility, a handheld model can help young surgeons grasp the fundamentals of anatomy in relation to the risks of surgical approaches.
Whether actual physical models versus computer 3-D reconstructions alone are most feasible and practical remains unknown. Nonetheless, access to such information for safer surgical planning will undoubtedly benefit patients in the future.
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