Personalized 3D Printing of Heart Model Aids in LAA-Closure Procedure: Case Report

July 17, 2015

SYDNEY, AUSTRALIA — Australian physicians are taking advantage of 3D printing to create an exact replica of the patient's cardiac anatomy when planning left atrial appendage (LAA) closure procedures with the Watchman (Boston Scientific) device[1].

The researchers say that 3D printing is useful when closing the LAA with the Watchman, particularly in patients where "the anatomy is complex and the interaction between the device and the appendage is difficult to quantify, even using advanced imaging methods."

Speaking with heartwire from Medscape, lead investigator Dr James Otton (Victor Chang Cardiac Research Institute, Sydney, Australia) said percutaneous LAA-occlusion procedures with the Watchman, which was approved by the US Food and Drug Administration (FDA) in March 2015, are performed under fluoroscopy and transesophageal echocardiography (TEE). In addition, multidetector computed tomography (CT) helps provide a 3D image of the heart.

"The issue is that the structure of the left atrial appendage is very complex, and even if you have a great-quality data set, it's very difficult to know where the device will fit within the left atrial appendage," said Otton. "The sizing is not straightforward. Within the orifice of the left atrial appendage, it can be hard to decide exactly where the device should go."

Watchman in 3D-printed model of LAA [Source: Dr James Otton]

In a letter to the editor in the June 2015 Journal of the American College of Cardiology: Cardiovascular Interventions, Otton and colleagues published data on their experience with 3D printing of the LAA in a 74-year-old man with a history of paroxysmal atrial fibrillation who was intolerant to oral anticoagulation. Using data from the CT scan, they printed a 3D model, which is made up of a rubberlike material to simulate atrial mechanical properties of the left atrium and LAA.

The 21-mm, 24-mm, and 27-mm Watchman devices were placed into the 3D model, which was then reimaged with CT. With the three devices in the 3D model, they were able to analyze the anatomic deformation for each device. This helped "identify the areas and extent of engagement of the device on the flexible atrial model," according to the investigators.

Interestingly, based on the TEE, the group reports the 21-mm device would have been selected but the data from CT scan of the 3D model suggested it would have been too small. Data from the 3D model/CT scan showed the 27-mm Watchman device was too large to be selected for the patient. As a result, the 24-mm device was chosen and deployed by Dr Brendan Gundalingam (Victor Chang Cardiac Research Institute). Intraoperative TEE revealed good positioning with no leakage.

To heartwire , Otton said calculating measurements using CT and TEE to appropriately size the Watchman device can be time consuming, but with the 3D printing, "you just stick the device in and you know exactly how it's going to fit."

Not all complications from LAA-closure procedures arise from inappropriate sizing of the device. Incomplete closure of the device and pericardial effusion are two detrimental outcomes that appear to be related to the poor sizing of the device within the LAA, however. For example, in the 74-year-old patient, they found the larger 27-mm Watchman device hadn't fully expanded. As a result, one of the unretracted Watchman "barbs" was applying a lot of pressure on a single point within the LAA wall. The group hypothesized that this might have led to a postprocedure pericardial effusion.

Otton said the 3D printing of a patient's left atrium/LAA can be done within 30 minutes of the CT scan. It is also surprisingly cheap, he added, noting the material costs of the 3D print range from $100 to $200, although there are software and other ancillary costs. At present, 3D printing for LAA-closure procedures with the Watchman is not done regularly and might not need to be done in patients where anatomy is straightforward and measurements easy to calculate, but Otton believes the technique can be useful as an adjunctive technology, particularly in the planning stages.

"I don't want to overstate the utility of [3D printing], because this is really just proof of concept, showing that it can be done," Otton told heartwire . "I think 3D printing will be used more—even in our own work it's been used in other procedures—and I think it will be useful in a subset of complex procedures. And it'll definitely be useful in education and planning, but I wouldn't go so far as to say it'll be routinely done. I think we'll have to wait a year or two to see how it goes."

Otton et al report no relevant financial relationships.

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