3D printing is a powerful technology that continues to improve medical practice. Its impact on percutaneous left atrial appendage (LAA) occlusion as an alternative therapeutic approach to medical therapy for stroke prevention continues to evolve as the technology advances.
The left atrial appendage (LAA) is a small, ear-shaped pouch in the muscle wall of the left atrium. In normal hearts, the heart contracts with each heartbeat, and the blood in the left atrium and LAA is squeezed out of the left atrium into the left ventricle When a patient has atrial fibrillation, the electrical impulses that control the heartbeat do not travel in an organized manner through the heart. Instead, many impulses begin simultaneously and spread through the atria. These rapid and chaotic impulses do not give the atria time to contract and/or effectively squeeze blood into the ventricles. Because the LAA is a little sac, blood collects there and can form clots. When these clots are pumped out of the heart, a stroke can occur. People with atrial fibrillation are 5 to 7 times more likely to have a stroke than the general population.
Atrial fibrillation (AFib) is the most common heart rhythm abnormality, affecting more than 33 million people worldwide and is highly associated with not only increased risk of cerebral stroke, but also sudden death, heart failure, impaired quality of life, and poor exercise capacity [1). Oral anticoagulation (OAC) is widely used for the conventional treatment of stroke prevention; however, it can trigger bleeding events and may be contraindicated in some cases. As an effective alteration therapy to OAC, catheter-based LAA occlusion, a promising nonpharmacological approach, has been recommended in the latest released guidelines of the European Society of Cardiology (2).
Accurate information about anatomical structure of the LAA is essential for its successful occlusion for stroke prevention. Obtaining this information is quite challenging. LAA anatomy — a structure known to be highly variable in geometry — is complicated and it is hard to quantify the interaction between the device and the appendage even with advanced imaging techniques. Sizing is traditionally done with transesophageal echocardiography (TEE) but this is not always precise, as it fails to provide a full-view outline image of the LAA. A number of recent studies report the benefits of using 3D printed patient-specific models (PSMs) to overcome these challenges and gain a better understanding of complicated cardiac anatomy to facilitate optimal sizing and placement of the LAA device.
Recently, Obasare and his colleagues at the Einstein Heart and Vascular Institute, Einstein Medical Center (Philadelphia, PA) published a study of 24 patients (14 with TEE and 3D PSMs, 10 with TEE alone) who underwent closure with the Watchman device (WD) (Boston Scientific, Marlborough, MA). Their findings conclude, “PSMs of the LAA improve precision in closure device sizing,” and “Use of the printed model allowed rapid and intuitive location of the best landing zone for the device.”
“The 3D PSM correlated perfectly with implanted device size (R2 = 1; p < 0.001), while TEE-predicted size showed inferior correlation (R2 = 0.34; 95% CI 0.23-0.98, p = 0.03). The PSM model better predicted final WD size than TEE (100 vs. 60%, p = 0.02). Use of the model was associated with significantly reduced procedure time (70 ± 20 vs. 107 ± 53 min, p = 0.03), anesthesia time (134 ± 31 vs. 182 ± 61 min, p = 0.03), and fluoroscopy time (11 ± 4 vs. 20 ± 13 min, p = 0.02). Absence of peri-device leak was also more likely when the model was used (92 vs. 56%, p = 0.04). There were trends towards reduced trans-septal puncture to catheter removal time (50 ± 20 vs. 73 ± 36 min, p = 0.07), number of device deployments (1.3 ± 0.5 vs. 2.0 ± 1.2, p = 0.08), and number of devices used (1.3 ± 0.5 vs. 1.9 ± 0.9, p = 0.07).”
These findings were further corroborated by the Department of Cardiology, Friedrich-Alexander-University Erlangen-Nürnberg (Erlangen, Germany). These researchers prospectively compared 3D PSM prediction of device size and compression to the standard TEE approach in 22 patients with atrial fibrillation who underwent LAA closure with the WD. Predicted device size based on simulated pre-operative implantation in the 3D PSM was equal to the device size finally implanted in 21/22 patients (95%). TEE alone would have undersized the device in 10/22 patients (45%). Device compression determined in the 3D PSM corresponded closely with compression upon implantation (16±3% vs. 18±5%, r=0.622, p=0.003). This is a significant finding given the importance of this indicator. An optimal compression of 8-20% has been emphasized to ensure a sufficient pressure on the LAA wall to minimize the risk of embolization and residual leakages (3).
In summary, use of 3D PSMs for percutaneous LLA occlusion delivers both clinical and economic benefits to patients, providers, and payers alike. When used for pre-surgical planning, they can reduce the duration of the operation and the use of contrast agents, anesthesia, and X-rays alleviating added risks to the patient. Using a 3D PSM to simulate the release of the appendage occluder to determine the device size and the axis of placement offers high potential value to all stakeholders– minimizing device waste, reducing procedural complications, such as leakage or device migration due to under-sizing, lowering downstream re-intervention costs, enhancing patient satisfaction and, ultimately, improving procedural outcome, increasing operating room efficiency and throughput.
So what’s on the horizon? A new study published in Nature Biomedical Engineering describes CT-guided 3D printing of personalized occluders to reduce the risk of incomplete closure of the LAA. Because the LAA shape is highly variable, one-size-fits-all LAA closure devices tend to incompletely occlude the pouch, leaving the stroke risk unchanged. Combining their expertise in cardiology, biomedical engineering, materials, and manufacturing, Dalio Institute of Cardiovascular Imaging at New York–Presbyterian Hospital and Weill Cornell Medicine developed a methodology for the production of personalized cardiovascular implants which may offer new hope as a nonpharmacological alternative for those patients whose anatomy makes occlusion challenging using today’s available devices. Learn more about this ground breaking work from its lead author.
References
https://news.osu.edu/news/2018/03/05/heart-valve-replacement/
