Getting tothe Heartof the Matter

Case Study

Breathing New Life, One Breath at a TimeChildren’s Hospital Colorado, a leader in pediatric heartcare, is improving the lives of children with complex
congenital heart disease with the help of patient-specific
3D models. As a referral center, it sees some of themost complicated congenital heart defects. One suchcase was a 4-year-old child born with tricuspid atresia, acongenital heart defect that affects approximately
1 in 10,000 births in the United States. Children with thiscondition are born with low oxygen concentrations in thearterial blood and are referred to as cyanotic. A seriesof palliative surgeries are typically undertaken to restore
a more normal oxygen saturation level and improve life
expectancy and quality of life. For Children’s Hospital
Colorado, this defect is not that rare. It successfully
treats many children with tricuspid atresia each year.

What I learned from the model
had a big impact not only on ourability to successfully complete
the ablation, but also on mysurgical approach. The way
things laid out in surgery wasexactly what I expected basedon the model. It gave me an
accurate understanding of all
the anatomical relationships,including the malposition of thegreat arteries and the enlarged
aorta that arose from theunusual position of the small
right ventricle.”
Max Mitchell, M.D.

Children’s Hospital Colorado

2“I gave her the best-informed
surgical treatment possible
thanks to the model andshe continues to do well
post-operatively.”
Max Mitchell, M.D.

Children’s Hospital Colorado

Case Study

However, this particular case presented a uniquechallenge because it involved an extremely rarevariant in which the ventricular cardiac chambers
were arranged in a superior-inferior position
compared to the typical side-by-side arrangement.
The mass or apex of the heart was pointed to
the right instead of its normal left position. The
great arteries were oriented opposite their usual
relationship to each other and both originated fromthe upper small right ventricle. The right ventricle wassupplied from the left ventricle through a large holecalled a ventricular septal defect. The smaller atrial
chambers that collect blood coming back to theheart were rotated posteriorly and to the left, resulting
in a plane of division that was much more transverse
than usual.
This highly unusual anatomy was also complicatedby Wolff-Parkinson-White (WPW) syndrome. Thiscondition involves an accessory electrical pathway
between the ventricular and atrial chambers that
leads to dangerously fast heart rates. In a patientwith only one functional ventricle, WPW syndrome isextremely perilous and if unaddressed, increases therisk of death following cardiac surgery.

The patient had undergone two previous palliative
surgeries but because of the discovery of WPWsyndrome, she was referred to the Heart Institute atChildren’s Hospital Colorado.

It Takes a Team to Mend a Broken HeartMax Mitchell, M.D., a congenital cardiac surgeon,and Kathryn Collins, M.D., a pediatric cardiologist
specializing in electrophysiology, reviewed the child’s
history to determine her next treatment steps. At
birth, her tricuspid valve that normally controls bloodflow from the right atrium to the right ventricle was
not formed, preventing blue blood from getting to
her right ventricle and out to her lungs. The main
pulmonary artery was also too small to provide
adequate blood supply to her lungs. A hole between
the right and left atria, known as an atrial septal
defect, allowed a mix of oxygen-rich and oxygenpoor blood to be pumped through her body.

3To address these issues and enable the child togrow, a shunt had been placed in her as a neonate
between the pulmonary artery and the aorta allowing
blood to get to the lungs. And at 12 months of age,
she underwent a bi-directional Glenn procedure, thefirst in a two-stage surgical strategy that bypasses
the heart entirely and pumps blood returning fromthe tissues directly to the lungs.

a catheter to the accessory pathway. Dr. Collins
attempted to ablate the accessory pathway inthe catherization laboratory, but was unable tocontact the accessory pathway due to the markedly
abnormal anatomy. As a result, she approached Dr.
Mitchell to gauge the feasibility of a surgical ablation
at the time of the planned Fontan operation.

After the Glenn procedure, Dr. Mitchell and hiscolleagues determined that the child was acandidate for the next stage of surgery known
as the Fontan procedure, the second in thetwo-stage surgery.

3D Patient-Specific Model Guides the Pathto New HopeHowever, a successful Fontan procedure is highly
dependent on a normal heart rhythm and heart rate.
The arrhythmia associated with WPW syndrome
had to be addressed either prior to surgery inthe catheterization lab or at the time of surgery.
In addition, it was imperative that her accessory
electrical pathway be ablated prior to completionof the surgery because it would be impossible toaddress in a catheterization laboratory after theFontan procedure, and because all the venous
connections from her body to her heart would
no longer exist. This would leave no route to getCase Study

Figure 1a

Figure 1b

Figures 1a, 1b and 1c: Patient cardiac MRI with and without contrast.

Even for experienced congenital heart surgeons,
echocardiograms are not easily related to 3D
anatomy in complex, rare cardiac anomalies.
After reviewing an MRI scan of the patient’s heartwith 3D reconstructions, Dr. Mitchell was concernedthat a surgical ablation carried a high risk of failure(Figures 1a, 1b, 1c).
He approached colleagues at the University ofColorado Anschutz Medical Campus to have a 3D
patient-specific model printed and cut into sections
for a better understanding of her cardiac anatomy.
The model needed to be printed with materials thatsimulated the look and feel of the patient’s heart.

Figure 1c

4The hope was that this would guide a successful
second attempt at ablation in the catheterization lab.
Lorna Browne, M.D., the lead radiologist on the case,prepared the scans and teamed up with designers atInworks, a design studio at the University of Colorado
Anschutz, to create the 3D model (Figures 2a, 2b,and 2c).
Nicholas Jacobson, the design lead on the case, andHayden McClain, student assistant, helped design
the 3D printing process for presurgical planningwith the team — orchestrating early brainstorms
to determine the design of the model that would
be used. Dr. Michael DiMaria, lead cardiologist on
the case, was instrumental in guiding Jacobson in
determining which anatomy was crucial to capturein the model due to his intimate knowledge ofthe patient’s diagnosis. Designed to fit the team’s
surgical specifications, the model was ultimately
created using a custom Agilus30™ and Vero™ White
multimaterial blend.

Case Study

In preparing for the electrophysiology (EP) lab
procedure, Dr. Mitchell and the cardiology teamused the model to plan the approach. The flexible
and functional nature of the model allowed themto stretch and pull certain areas to understand theinterior topology and flow paths. The EP team used
the MRI overlaid on the lab’s intracardiac navigation
system with concurrent real time transesophageal
echocardiography.
“What I learned from the model had a big impact
not only on our ability to successfully complete theablation but also on my surgical approach. The waythings laid out in surgery was exactly what I expectedbased on the model. It gave me an accurate
understanding of all the anatomical relationships,
including the malposition of the great arteries andthe enlarged aorta that arose from the unusual
position of the small right ventricle,” Dr. Mitchell
added. “I did the operation differently from my usualapproach based on the information the model
provided. Holding the model in my hand allowed me
to visualize what I would see in surgery and fromthat I was able to plan a more informed approach,which allowed me to go into the surgery with more

Figure 2aFigure 2a: Functional model created using a custom Agilus30™ andVero™ White multimaterial blend.
Figure 2b

Figure 2b: Model in figure 2a cut into three sections for the electrophysiologist
to determine the optimal approach to device placement.
Figure 2c

Figure 2c: Model in figure 2a strategically cut and stretched for the cardiac
surgeon to get an optimal view of the inside of the heart to determine thebest surgical approach.

5

Figure 3a

Figure 3b

Figure 3a: Visual model created using hemodynamic data combined with patient
anatomy to show blood flow. This model helped the medical team understand areasof the heart that they could access without disrupting blood flow.
Figure 3b: Hemodynamic data used to create
the multimaterial 3D print shown in figure 3a that
demonstrates the blood flow pathways.

confidence. The model also allowed me to design
a more efficient Fontan for her and do it safely
through all of the scar tissue that was there fromprevious surgeries.”

Case StudyDr. Mitchell said, “With that model and having it
cut into the appropriate planes, we were able togo into the EP lab with our electrophysiology andechocardiography teams and pinpoint the catheter
location inside the child’s heart within millimeters.
Using their navigation system, the echocardiogram
and the models, all simultaneously, we were all able
to stay oriented during the ablation and were visuallyable to anticipate the pathway to the suspected
location of the accessory pathway. This facilitated Dr.
Collins’ ability to guide the catheter to the accessory
pathway and achieve a successful ablation.”
To further assess the movement of blood throughher heart, Dr. Mitchell’s research team performed a4D-MRI flow analysis. This allows the investigator topicture the blood flow through the heart and into theblood vessels. Due to the very unusual orientation of
the takeoff of her aorta, Dr. Mitchell suspected thatblood flow through the ventricles and into the aorta
would be highly abnormal and likely inefficient. This
proved correct, and he requested a multimaterial

3D print of the heart demonstrating the very unusual
blood flow pathways prior to surgery (Figure 3a).
Dr. Alex Barker, the Director of the Advanced Imaging
Lab and early pioneer of the 4D Flow MRI imaging
process, worked with Dr. Mitchell and Jacobson togenerate and extract the 4D flow data into a format
that could be used to 3D print the new heart model.
Each color used in the model was coded toa velocity (Figure 3b). “The model provided
comprehensive flow hemodynamic information ateach anatomic region throughout the cardiac cycle.
It demonstrated that everything about the flow in
her heart was highly abnormal and confirmed thather pumping efficiency would likely remain more
inefficient after the Fontan procedure comparedto patients with more typical tricuspid atresia. Thisadvanced 4D-Flow MRI analysis model provided
valuable information to direct future potential
management changes,” stated Dr. Mitchell.
Ultimately, both the surgeon and the patient
benefited from this personalized approach to medicaltreatment. Dr. Mitchell summed it up, “I gave her
the best-informed surgical treatment possible
thanks to the model and she continues to do well
post-operatively.”6Stratasys Headquarters

Case Study

7665 Commerce Way,
Eden Prairie, MN 55344+1 952 937-3000 (Intl)+1 952 937-0070 (Fax)

1 Holtzman St., Science Park,PO Box 2496
Rehovot 76124, Israel+972 74 745 4000+972 74 745 5000 (Fax)stratasys.com
ISO 9001:2015 Certified© 2020 Stratasys Ltd. All rights reserved. Stratasys, Stratasys signet, Agilus30 and Vero are trademarks or registered trademarks of Stratasys Ltd.
and/or its subsidiaries or affiliates and may be registered in certain jurisdictions. All other trademarks belong to their respective owners. Productspecifications subject to change without notice. Printed in the US. CS_PJ_ME_4D Medical Case Study_0220a