3D printing of left atrial appendage for personalized planning of catheter-based occlusion: Seeing is believing, but touching is the truth
Presentation and treatment
A 74-year-old man with a history of paroxysmal non-valvular atrial fibrillation (AF) and transient ischaemic attack (TIA) despite oral anticoagulation was referred for catheter-based left atrial appendage (LAA) occlusion.
Multidetector CT (MDCT) showed an LAA with a narrow ostium (black dashed line) and a wider neck (black solid line), potentially increasing the difficulty of device sizing and positioning. (Figures A and B) It was thought that successful LAA occlusion may be made more challenging by this anatomy.
For better planning, we decided to simulate the actual procedure using 3D printing technology. A computer-based hollow cast of the LAA was created from the MDCT data set, which was then converted to a stereolithography file for 3D printing using dedicated software (Mimics, Materialise Software, Leuven, Belgium). An LAA model made of photosensitive resin was fabricated by 3D printing. En face view of the 3D replica revealed that the LAA ostium had a 3D spiral configuration (black dotted line), a complex anatomy that was not appreciated on tomographic or silhouette images. (Figure C)
Three Watchman LAA closure devices (21 mm, 24 mm and 27 mm in size) were separately tested on the 3D model. After several experimental tests, the 24 mm device was found to completely seal the LAA without peri-device leak or insecure anchor. In both the simulation and actual procedures, the superior edge of the polyethylene terephthalate (PET) cap was securely positioned inside the LAA (green dashed line) with the inferior edge (red dashed line) partially protruding outside, yet achieving complete seal. (Figure D, simulation; Figure E, actual procedure) The black dotted line in Figures D and E denotes the nitinol frame of the device.
Percutaneous LAA occlusion has emerged as an alternative therapeutic approach to medical therapy for stroke prevention in patients with AF. The anatomy of the LAA is variable but important to evaluate prior to device implantation because it influences device selection and procedural success. Since the LAA occluder device is designed to cover the ostium and anchor in the neck, complete evaluation of the LAA with transoesophageal echocardiography (TEE) and a CT scan is recommended to define the morphology of the ostium, the width of the landing zone, and the length and shape of the LAA.
Before device release, the four “PASS” criteria should be met: 1) position (device distal or at LAA ostium, protrusion of shoulder by <40 percent to 50 percent of device depth is acceptable); 2) anchor (testing stability by retracting the deployment knob and letting go, to assess return to original position); 3) size (device shoulder compressed 8-20 percent of original size on TEE); and 4) seal (assess TEE for any residual flow, must be <5 mm before release). When it comes to complex cases, these criteria are difficult to meet. During device implantation procedures, multiple attempts may be required, which are likely to result in pericardial effusions.
Currently, display of images is mostly still 2D (ie, on a flat screen) in laboratories despite the availability of modern imaging techniques that allow 3D virtual visualization of the LAA. The rapid development of 3D printing technology enables the creation of patient-specific models of various anatomical cardiac structures, allowing clinicians to optimize procedural planning by holding in their hands the physical replica of the patient-specific LAA and tangibly appreciating its 3D anatomy. Furthermore, it is possible to perform personalized device testing on the LAA physical model before actually performing the procedure in the patients. This has the potential to reduce procedure time, optimize procedural success and enhance procedural safety.
This case demonstrates the clinical utility of 3D printing in guiding the choice of the LAA closure device, ensuring complete seal and avoiding procedural complications. Physical models are particularly pertinent to LAA occlusion where the anatomy is complex and the interaction between the device and the appendage is difficult to quantify, even using advanced imaging methods.