The human heart beats an astonishing 115,000 times each day. It's a fascinating (and essential) organ, which is why we are highlighting the heart and its support structures in this week's post, as well as sharing some intriguing STL files so you can create your own heart 3D model by using your own 3D printer. In this week's post, we will introduce you to the top 3D-printable STL files published on the embodi3D® website. Before you get started creating your own heart 3D model, you will need to register through embodi3D® (https://www.embodi3d.com/register/). Registering is absolutely free, so become a member today!

We recently reported on how researchers have used a 3D printed heart to treat arrhythmia, yet 3D printing is also be used to combat other types of cardiovascular disease. After all, heart disease is the leading cause of premature death in Western countries. According to the National Institutes of Health, nearly half a million individuals succumb to cardiovascular disease each year. While coronary artery disease leads the pack in terms of cardiovascular diseases, congenital heart conditions and acquired diseases of the heart such as tumors, cardiomyopathy, pericardial processes, and valvular disease unfortunately remain present in the modern era. In the early 2000s, an average 1.5 million patients received some type of invasive heart catheter, a figure brought to our attention through the book "Computed Body Tomography with MRI Correlation, Volume 1" (edited by Joseph K. T. Lee). The answer to reducing the number of invasive heart procedures may be in medical 3D printing, whether CT scans can be converted into STL files in order to create 3D models of the heart and nearly every part of the human anatomy. 

Medical 3D Printing and STL Files: An Alternative to Invasive Cardiac Catheterization?

Echocardiography is widely available, portable, and essentially non-invasive when compared to MDCT and MR scans, while CT and MRI scans give us a clear advantage in terms of creating output files that are ready to be converted into a 3D printing-ready format such as STL (stereolithography) files. STL files and tissue algorithm conversion technologies from companies such as embodi3D® are bringing medical 3D printing within reach of researchers, radiologists, physicians, and medical students. Radiologists have witnessed the evolution of medical imaging, from two-dimensional scans to the three-dimensional scans aided by the latest technologies. 3D-printable files open the door to less invasive diagnostic procedures and have also proven useful in pre-surgical planning. 

Multiplanar imaging with computed tomography (CT) and magnetic resonance imaging (MRI) gave rise to 3D reconstructions, improving the evaluation of complex anatomies. Medical 3D printing takes imaging data from the limited two-dimensional view on a computer screen to a three-dimensional model that can be held, studied, and referenced. 

The Meteoric Rise of Additive Manufacturing in Medicine

The additive manufacturing technique known as 3D printing has seen exponential growth in health care sectors over the last decade, with most of that growth coming in just the last few years. As a tool to improve patient care and lower the costs of care, 3D printing can be used in pre-operative planning, education, and also to replace bone materials, such as knee joints. For these reasons, the McKinsey Global Institute recently called 3D printing a "disruptive technology that will transform life, business and the global economy." This management consulting company also predicated that 3D printing will have impact the global economy by a range of $200 billion to $600 billion in the coming decade. What started out as a technology for garage tinkerers and those looking to replace hard-to-find mechanical parts was only recently introduced into the medical world. The adoption rates of this technology within the health care community have been staggering. In 2000, only six publications made mention of 3D printing's use in medicine. That figure had jumped to nearly 200 publications in the years spanning 2011 and 2015. This brings us to the present, where nearly 2,000 publications have cited the amazing utility of 3D printing across a diverse range of medical applications. The National Additive Manufacturing Innovation Institute was launched in 2012 as a way to grow and encourage the adoption of this life- and industry-changing technology.

3D Printing in Cardiology and Cardiothoracic Surgery

The use of 3D printing in cardiology to detect abnormal heart structures and predict heart attacks has followed a similar growth trend in the past decade. In the research article "Cardiac 3D Printing and its Future Directions," Vukicevic, et al. detailed the utility of 3D printing in the area of cardiovascular care, focusing primarily on acquired structural heart disease. 3D-printed heart and aortic models have been used for treatment planning in both percutaneous cardiology applications and cardiothoracic surgery. In cardiothoracic surgery, 3D-printed anatomic models have been used to plan surgical approaches, perform resections, and guide the process of tissue reconstruction.

Computed tomography angiography (CTA) is frequently performed before catheter-based and surgical treatments in situations of congenital heart disease (CHD). To date, little is known about the accuracy and advantage of different 3D-reconstructions in CT-data. For reference purposes, gaining the exact anatomical information is critical in achieving a successful outcome. According to a review published in JACC: Basic to Translational Science, 3D models may improve outcomes in patients with congenital heart disease by also improving communication among multidisciplinary teams, enhancing shared decision-making, and facilitating greater medical breakthroughs via basic science and translational clinical investigations. Approximately 3 out of 1,000 patients with congenital heart disease require a surgical or catheter-based intervention early in their lifetimes, according to the study's investigators. 3D printing can be a valuable tool to plan extra-cardiac and vascular surgery in patients with CHD. 3D models are helpful for planning high-risk unifocalization surgery. 

Medical 3D Printing as an Educational Tool in Congenital Heart Disease

In terms of education, the use of medical 3D printing technology may lead to an educational shift from an apprenticeship-type model to a simulator-based learning method, which would augment the traditional mentored training. Using 3D printed models in congenital heart disease (CHD) can reduce the learning curve for cardiac trainees in three crucial ways: help trainees understand the complex cardiovascular structures, provide high-fidelity simulation experiences, and enable more exposure to rare CHD cases.

1. A 3D-Printable Model of a Human Heart from Contrast-Enhanced CT Scan

A 3D-printable model of a human heart was generated from a contrast-enhanced CT scan. An endpoint of many patients with coronary heart disease (CHD) is heart failure requiring a ventricular assist device (VAD) or heart transplant. 3D printing can aid in ventricular assist device placement and optimizing function in complex CHD, as recently described by Farooqi et al. and Saeed et al. 

2. 3D-Printable STL File of Truncus Arteriosus with Unseparated Aorta and Pulmonary Artery

  Truncus arteriosus is a congenital (present at birth) defect that occurs due to abnormal development of the fetal heart during the first 8 weeks of pregnancy. The heart begins as a hollow tube, and the chambers, valves, and great arteries develop early in pregnancy. The aorta and pulmonary artery start as a single blood vessel, which eventually divides and becomes two separate arteries. Truncus arteriosus occurs when the single great vessel fails to separate completely, leaving a connection between the aorta and pulmonary artery. This model is provided for distribution on Embodi3D with the permission of the author, pediatric cardiologist Dr. Matthew Bramlet, MD, and is part of the Congenital Heart Defects library. We thank Dr. Bramlet and all others who are working to help children with congenital heart problems lead normal and happy lives.

3. STL Files of a Neonatal Heart Defect (Ventricular Septal Defect)

 Ventricular septal defect (VSD) with pulmonary atresia (PA) can be considered to be the severest form of tetrology of Fallot wherein the right ventricular outflow tract obstruction has progressed to the extent of atresia. This atresia can occur either at the infundibulum or as a plate atresia of the pulmonary valve. An important observation is that the plate-type atresia is more frequently associated with well-developed pulmonary arteries. The other significant abnormality in patients with VSD and pulmonary atresia (PA) is the presence of arborization abnormalities. The blood supply to a particular lung segment can be derived from a systemic artery or a central pulmonary artery or a combination of both.

4. 3D-Printable Heart Model Showing Tetralogy of Fallot

 Tetralogy of Fallot, which is one of the most common congenital heart disorders, comprises right ventricular (RV) outflow tract obstruction (RVOTO) (infundibular stenosis), ventricular septal defect (VSD), aorta dextroposition, and RV hypertrophy (see the image below). The mortality rate in untreated patients reaches 50% by age 6 years, but in the present era of cardiac surgery, children with simple forms of tetralogy of Fallot enjoy good long-term survival with an excellent quality of life. This three-part 3D printed heart is from a CT scan of a 4-year-old infant with Tetrology of Fallot, a congentital heart defect and the most common cause of blue baby syndrome.

5. 3D-Printable STL of Left Heart Atrium and Ventricle

    3D models promise to transform teaching in ways that go beyond the lecture hall, and over the next few years are set to revolutionize medical training, especially in percutaneous interventions. In this 3D model we can observe the anatomical relationship of all the elements of the heart and neighboring structures.

6. Left Main Coronary Artery with Abnormal Origin Rising from Pulmonary Artery Trunk

 Variations in coronary anatomy are often seen in association with structural forms of congenital heart disease like Fallot's tetralogy, transposition of the great vessels, Taussig-Bing heart (double-outlet right ventricle), or common arterial trunk. Importantly, coronary artery anomalies are a cause of sudden death in young athletes even in the absence of additional heart abnormalities. Prior knowledge of such variants and anomalies is necessary for planning various interventional procedures.

7. Aortic Coarctation in 3D-Printable STL File

  Coarctation  of the aorta — or aortic coarctation — is a narrowing of the aorta, the large blood vessel that branches off your heart and delivers oxygen-rich blood to your body. When this occurs, your heart must pump harder to force blood through the narrowed part of your aorta. Coarctation of the aorta is generally present at birth (congenital). The condition can range from mild to severe, and might not be detected until adulthood, depending on how much the aorta is narrowed. Coarctation of the aorta often occurs along with other heart defects. While treatment is usually successful, the condition requires careful lifelong follow-up.

8. STL File of a Cardiac Myxoma

  The World Health Organization (WHO) defines a cardiac myxoma as a neoplasm composed of stellate to plump, cytologically bland mesenchymal cells set in a myxoid stroma. Myxomas can recur locally (usually with incomplete resection) and spread to distant sites through embolization. Embolization appears to be much more likely in myxomas that are friable with a broad-based attachment than they are in tumors that are fibrotic or calcified.

9. 3-D Printable Heart Anatomy from High-Spatial Resolution Imaging

A heart 3d model with details of anatomy. By combining the technologies of high-spatial resolution cardiac imaging, image processing software, and fused dual-material 3D printing, several hospital centers have recently demonstrated that patient-specific models of various cardiovascular pathologies may offer an important additional perspective on the condition. With applications in congenital heart disease, coronary artery disease, and in surgical and catheter-based structural disease – 3D printing is a new tool that is challenging how we image, plan, and carry out cardiovascular interventions.

10. Human Heart Model in Stable Slices from Contrast-Enhanced CT Scan

A 3D printable model of a human heart was generated from a contrast-enhanced CT scan

References

1 Yoo, S. J., Spray, T., Austin, E. H., Yun, T. J., & van Arsdell, G. S. (2017). Hands-on surgical training of congenital heart surgery using 3-dimensional print models. The Journal of thoracic and cardiovascular surgery, 153(6), 1530-1540.

2. Farooqi K.M., Saeed O., Zaidi A., et al. (2016) 3D printing to guide ventricular assist device placement in adults with congenital heart disease and heart failure. J Am Coll Cardiol HF 4:301–311.

3. Saeed O., Farooqi K.M., Jorde U.P.  (2017) in Rapid Prototyping in Cardiac Disease, Assessment of ventricular assist device placement and function, ed Farooqi K.M. (Springer International Publishing, Cham, Switzerland), pp 133–141.

4. Lee JKT, Sagel SS, Stanley RJ, Heiken JP. Computed Body Tomography with MRI Correlation. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.

5. Ballard, D. H., Trace, A. P., Ali, S., Hodgdon, T., Zygmont, M. E., DeBenedectis, C. M., ... & Lenchik, L. (2018). Clinical applications of 3D printing: primer for radiologists. Academic radiology, 25(1), 52-65.

6. Vukicevic, M., Mosadegh, B., Min, J. K., & Little, S. H. (2017). Cardiac 3D printing and its future directions. JACC: Cardiovascular Imaging, 10(2), 171-184.