There is an increasing need to exclude circulation within the left atrial appendage for patients with non-valvular atrial fibrillation; this can be an alternative therapy to prevent thromboembolism when there is a relative contraindication to anticoagulation (Holmes et al. 2014). The current standard of care uses TEE with fluoroscopy guidance, and there is an increasing interest to utilize data from a pre-intervention CT, akin to other methods for atrial fibrillation therapy. The left atrial appendage has a variable anatomy, and while there are now several devices available, there can be considerable debate and uncertainty regarding the optimum device sizing. Once the decision to use a device is made clinically, sizing is of paramount importance, since there can be serious complications to a procedure that leads to incomplete occlusion or to one that uses a device whose size exceeds the tolerance of the tissue. The role of 3D printing is to assist in best-sizing the device to determine the optimum dimensions and enabling simulation and education of the procedure. The latter application will benefit from new printing materials to better emulate myocardium.

Hypertrophic obstructive cardiomyopathy has a wide spectrum of disease states but in general has the pathophysiology of eccentric and regional hypertrophy of the left ventricle (Maron et al. 2016). While most patients are treated medically, myomectomy of the ventricular septum can be performed with the intended result of reducing the obstruction to the outflow of blood to the aorta (Gersh et al. 2011; Elliott et al. 2014; Maron et al. 2011). Imaging is usually performed with cardiac MRI. 3D models offer a unique perspective of the 3D orientation of the outflow tract and key haptic anatomical feedback (Yang et al. 2015) (Fig. 7.2). In theory, a 3D model that could incorporate the systolic anterior motion from the mitral valve anterior leaflet would be highly valuable as it could be connected to a flow pump to spatially comprehend the motion and its relationship to the outflow tract throughout the cardiac cycle.

3D printing provides advanced understanding of the relationship of the unusual cardiovascular tumors for which intervention is a consideration. While 3D visualization, e.g., using customized MR acquisitions, can be adequate for delineating the myocardium, models can be useful to show the relationship between a mass and an adjacent structure that may be involved (Jacobs et al. 2008; Schmauss et al. 2013; Son et al. 2015; Al Jabbari et al. 2016).

The last decade has seen highly innovative treatment strategies for valve disease. Two major procedures that have been enabled by technique and device advances are transcatheter aortic valve repair (TAVR) (Schmauss et al. 2012; Webb and Lauck 2016) and transcatheter mitral valve repair (TMVR) . These two procedures share two main characteristics in common. First, they are far less invasive than conventional valve treatments that use open surgery. However, the second characteristic is a consequence of the first: without surgery, there is no opportunity to visually inspect and understand the true 3D representation of the valve anatomy. This can be highly relevant as the geometry differs among patients, and the experience of the operator in these relatively new procedures is variable. Consequently, 3D printing of valve pathology has emerged as a growing field, taking advantage of the ability of 3D printing to incorporate multimodality imaging, namely, echocardiography plus CT and MRI.

The number and scope of TAVR continues to grow (Webb and Lauck 2016), and it is now established that TAVR is a generally safe alternative to surgery for many patients (Nishimura et al. 2014; Moat 2016) and has an expanding role (Webb and Lauck 2016). While some procedures are straightforward, there is mounting evidence that 3D printing has a clear role to help delineate both the anatomy and the hemodynamics of pathology, as well as the effect of calcification for patients at higher risk for complications (Gallo et al. 2016). Valvular stenosis of the aorta is already well addressed by 3D printed models, and these models can be used to plan TAVR (Maragiannis et al. 2015) (Fig. 7.3). In some patients, the procedure is designed through the cardiac apex, where a printed model of the myocardium in addition to the valve can help plan intervention (Fujita et al. 2015). There is also an increasing interest in so-called “valve-in-valve procedures” where a second valve is placed within the first, generating another potential indication where a physical model can be used to classify patients into surgical versus percutaneous candidate, and when a second TAVR is considered, to determine the most accurate measurements that will lead to optimal choice of prostheses (Fujita et al. 2015).

The implementation of more flexible materials, and those that better mimic physiology in health and disease, is an important advance so that models can better emulate the impaired function of the stenosed aortic valve (Maragiannis et al. 2014). Regarding complications, there is ongoing debate regarding the significance of small paravalvular leaks. However, when a leak is characterized as moderate, there is a negative impact on valve function, as well as survival (Figulla et al. 2016). When intervention for a leak is considered the best management option, a percutaneous approach is often preferred (Sorajja et al. 2011), where models can help guide the procedure. Conversely, flexible 3D printed models of the aortic root complex derived from routine pre-TAVR CT (Dill et al. 2013) have been shown to predict paravalvular leaks after the procedure as determined by echocardiography (Ripley et al. 2016), which may help minimize this complication.

The success of less invasive interventions in the aortic valve has undoubtedly inspired approaches to treating mitral disease. Several studies support that the valve apparatus can be printed (Binder et al. 2000; Dankowski et al. 2014; Kapur and Garg 2014; Mahmood et al. 2014, 2015; Witschey et al. 2014). The imaging data required for these models is derived from echocardiography and CT, and there is growing evidence that this as an appropriate indication for 3D printing. For example, prints of normal versus regurgitant mitral valves (Witschey et al. 2014) have been used to determine the ring selection at annuloplasty and have been used to enhance spatial understanding of the 3D relationships at surgery (Owais et al. 2014) and estimate the risk of left ventricle outflow tract obstruction (Wang et al. 2016).

Regarding transcatheter approaches, these percutaneous techniques, in theory, are lower risk than their counterpart open procedure for functional mitral regurgitation (Figulla et al. 2016). As in TAVR, though, the lower risk from avoiding an open repair comes with the cost of reduced intra-procedure visualization, and there is an unmet need to correctly size the mitral annulus and to avoid obstruction of left ventricular outflow. Literature is beginning to support models for pre-percutaneous implantation of an annuloplasty system (Dankowski et al. 2014) as well as deployment of a MitraClip (Abbott Laboratories, Abbott Park, IL) (Little et al. 2016) (Fig. 7.4).