3.2. Cardiovascular System 3.2.1. Cardiothoracic. 3DP in cardiothoracic surgery has broad applications [97]. This section is focus on three significant applications: congenital heart defects (CHD) and mitral valve disease, pulmonary interventions, and for educational purposes. Congenital heart defects (CHD) present with a wide range of complex and unique structures. Traditional imaging methods such as CT, ultrasound, and MRI are not very useful for assessing the unique and usually intricate spatial relationships associated with CHD [98, 99], since its 2dimension projection differs significantly from the operating room reality. Therefore, 3D-printed models have significant advantages regarding presurgical planning and simulation of cardiac surgeries [100]. These models display with high fidelity the complex anatomical defects of patients with CHD and enable a comprehensive evaluation of the unique spatial relationships that other methods cannot obtain [101]. Several studies show the utility of 3D-printed models in clinical decision-making, interventional planning, facilitating communication between physicians and patients, and enhancing medical education for medical students and surgical residents [98–100, 102]. A recent systematic review assessing the current applications and the accuracy of 3DP for CHD concluded that patient-specific 3D models replicated with high accuracy complex cardiac anatomies demonstrate a substantial value in preoperative planning, surgical simulation, and decision-making and intraoperative orientation [103]. The mitral valve anatomy is difficult to assess, due to its relation to the left ventricular outflow tract (LVOT), its position in the posterior aspect of the heart, and the complex relation between the ventricle, subvalvular apparatus, and the LVOT. Since there are no medical options for the treatment for severe mitral valve regurgitation, its treatment relies on surgical repair or replacement, which faces many challenges [104]. From the steep learning curve, the success of the procedure is based on the surgeon expertise, to the difficult planning before interventions, since it is challenging the interpretation of the valve’s anatomy from a 2D or 3D echocardiographic projections [105]. Several authors have used 3DP to simulate different mitral valve pathological process, with rigid plastic and silicone-cast based on the 3D transoesophageal echocardiography. These models allow the physicians for preoperative planning and device testing on minimally invasive valve surgery simulators [106]. Preoperative planning with 3DP is useful for a transcatheter mitral valve replacement (TMVR), an alternative treatment for severe symptomatic mitral valve disease that is not amenable for surgery due to increased intraoperative risk [107]. TMVR has a highly prevalent complication which is LVOT obstruction after device placement (8.211.2%). By using a 3D anatomical model, the surgeon can insert a transcatheter valve into the model to simulate and delimitate the neo-LVOT, thus making the necessary modifications to the catheter used to avoid an obstruction after deployment [108]. 3DP plays a crucial role in the management of complex respiratory diseases. The high variability in the anatomy of the tracheobronchial tree [109] makes standardized interventional treatments very challenging especially for stent placement. Tracheobronchial stents are indicated to treat complex central airway obstruction with both intrinsic and extrinsic airway compression [110], to maintain airway patency and provide ventilation to the lung. Due to the broad variability on the diameter of the airway, angles of ramification of the main bronchus, a precise fit can be challenging to achieve, causing complications such as fracture and migration of the stent, formation of granulation tissue, and possible erosion and perforation of the trachea [111]. Patient-specific 3D stents made of different materials (silicone and elastic thermoplastic) that can produce nonstandard geometrical figures could help prevent the later complications associated with unfitted bronchial stents. Additionally, some groups are testing biodegradable stents, as used in cardiology, that could prevent all together the risk of having devices implanted indefinitely [112]. The utility of 3DP, as a didactic tool for educational purposes at every level of training, is extremely promising. 3D teaching engages visual and tactile representations that improve understanding of complex diseases such as CHD, achieving a rapid understanding of anatomical defects hard to depict on a 2D image [101, 113, 114]. Some studies have demonstrated that medical students perform better at identifying cardiac anatomy when using 3D-printed models vs. cadaveric traditional learning [115]. Other studies assessed the efficacy of 3D models of ventricular septal defects as part of a CHD curriculum for medical students showed a statistically significant difference between the experimental and control groups in satisfaction, perceived learning quality, and structural conceptualization [116] (Figure 3). 3DP will play a significant role in the future of care of CHD patients by promoting surgical interventions tailored to the unique CHD anatomy of each patient and creating a dynamic and real-life didactic tool for medical training and communication with patients and caregivers, since teaching patients their conditions with 3D models allows might give them more confidence in explaining their condition, knowledge on their disease, and overall improved satisfaction in the consult [100]. 3.2.2. Vascular. Since the first application of 3DP in vascular surgery, in which a life-size replica of the aneurysm was made prior to the endovascular procedure for surgical planning, many studies have been published in the last 20 years [118]. To date, no randomized controlled study on 3D prototyping in vascular surgery is available [119–121], and most of the published studies are descriptive and case series. 3DP in vascular surgery is mainly applied to (a) infrarenal and juxtarenal abdominal aorta aneurysms, (b) thoracic aortic aneurysms, and (c) other approaches to large vessels such as celiac trunk, splenic artery, carotid, subclavian, and femoral arteries, as well as the portal vein. Most vascular surgeons plan their surgeries using CT and magnetic resonance imaging, in some cases, also 6 BioMed Research International | The Surgical Technologist | APRIL 2022 258 JUNE 202 258
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