Denmark sisters transcend heart disease to grow families

by Zoe Bendoff

In June, Steffi Thiem found out she is pregnant with her fourth child, a baby girl due in March 2023.


There was once a time when Thiem and her younger sister, Cassi Oshefsky, thought they may never have children at all.


These two women would not be where they are today without life-changing care from creative doctors who strive to keep their patients’ hearts in good hands.

A pulsing discovery

Fourteen years ago, Thiem, then 17 and living in the family’s hometown of Luxemburg, east of Green Bay, went to the doctor for what she thought would be a normal checkup. There, her doctor discovered she had the same heart defect her younger sister, Oshefsky, was diagnosed with when she was born.


“I always felt really bad for [Cassi] because she had to go to all these checkups and worry about overdoing it in sports and stuff, and it honestly never crossed my mind that it could happen to me,” Thiem says.


This heart condition is called a bicuspid aortic valve. A typical aortic valve is meant to have three leaflets, which Thiem compares to the Mercedes-Benz emblem. Thiem and Oshefksy instead have a genetic condition where two of those three leaflets are fused. Because the heart is forced to work extra hard, those affected run the risk of their valve becoming too tight or too leaky.


Thiem had no choice but to put her health before her passions.


“When I found out, it was the beginning of my senior year,” Thiem says. “I played basketball my entire life. I couldn’t play my senior year because they didn’t want me running, so that was just very hard for me at the time.”


Oshefsky says she can’t imagine what Thiem went through navigating her new reality. Oshefsky never knew anything else. 


“When I was younger, I just thought, ‘I’m going to the doctor for a checkup,’ but really, it was a lot different than what other kids had to go through,” Oshefsky says.


The condition impacted the sisters’ lives in completely different ways, but they agree that it fostered their special bond.



Cassi Oshefsky and her husband Lucas are grateful for the care she received from Froedtert & Medical College of Wisconsin, which has allowed them to have a family. Photography by Ann James/Ann James Photography.

Regaining their rhythm

Four years after Thiem’s diagnosis, she went in for a routine visit with her cardiologist who noticed her valve looked enlarged. Thiem found out she would need valve-replacement surgery just two weeks later.


“It was a shock that you would go in for these checkups every year and you never thought you were gonna be told you had to have the surgery, so it was very overwhelming and scary,” Thiem says. 


Oshefsky remembers Thiem’s strength, which helped her get through her own procedure shortly after. 


“When [Steffi was diagnosed], she had such a short period of time that she thought about it before getting the surgery, whereas I had a full 18 years of going to all those appointments and meeting with the cardiologist,” Oshefsky says.


Oshefsky says it took time before the reality set in that she would eventually need surgery —  a procedure that inspired her current career as a licensed practical nurse. 


The sisters both made the difficult decision to replace their aortic valves with mechanical ones rather than the alternative: pig valves that often need replacement within 5-to-10 years. 


“At that time, it was like 2008 … they didn’t know if you could even have kids with the mechanical valve,” Thiem says. “I just remember it was so emotional trying to decide what to do because a pig valve doesn’t last forever.”


But at 21 years old, having children still felt a long way off.

Hearts in sync

Before Thiem knew it, she was sitting next to her husband, Mark, at their wedding reception.


Instead of clinking glasses to get couples to kiss, guests at weddings in the Green Bay area will sometimes play games or donate money for certain causes in exchange for kisses from the newlyweds. 


So, just as the Oshefskys did before at their wedding and Thiem and Oshefsky’s sister Lexi did at hers, the Thiems invited guests to donate to the American Heart Association. Thiem says the three weddings combined probably brought in over $6,000. The couples’ special days solidified more than their love for one another — they strengthened their devotion to helping others access the care Oshefsky and Thiem did, which helped them not only survive their heart disease but thrive.


But neither Thiem’s nor Oshefsky’s family was complete. 

Carrying a tiny heart

Dr. Meredith Cruz is a maternal fetal medicine specialist with Froedtert Hospital and the Medical College of Wisconsin, and co-director of Froedtert's heart disease and pregnancy Program. Photography by Medical College of Wisconsin.

The sisters once believed they may never safely have kids, but that changed five years ago when Oshefsky found out she was pregnant with her oldest daughter, Aubrey. 


Oshefsky’s doctor immediately referred her to the Froedtert & Medical College of Wisconsin Heart Disease in Pregnancy Program in Milwaukee, co-directed by heart specialist Dr. Scott Cohen and maternal fetal medicine specialist Dr. Meredith Cruz.


Cohen says they designed the program in 2016 knowing women born with congenital heart disease are living into childbearing years, and their heart disease may put them at risk during pregnancy. Before the program began, he says he remembers a handful of times when patients’ and their mothers’ jaws dropped at the news they could safely carry out pregnancy with the right care.


Because the cardiovascular system goes through changes throughout pregnancy, during delivery and after women give birth, Cohen says care needs to be coordinated collaboratively between a group of experts. 


Cruz says their program stands out as the only one in the state with an approach that involves every specialist needed to care for these women throughout their high-risk pregnancies.


“It really takes us talking as a group in the same room to come up with a comprehensive delivery plan to keep these patients safe,” Cruz says.


Two months after Oshefsky found out she was pregnant, Thiem also found out she was expecting her first child, beginning the sisters’ shared, ongoing journey with Froedtert.


 “[The team] gave us a plan,” Oshefsky says. “I felt comfortable the whole time with what their plan was. They explained it very well, and I felt like I was in good hands.”


The sisters first switched from the blood thinners they took to prevent clots in their mechanical valves to injections that wouldn’t cross through the placenta. 


Because Cohen also serves as program director of the Adult Congenital Heart Disease Program at Children’s Wisconsin, he met the sisters at his monthly clinic in Green Bay and coordinated their care with Froedtert until they approached their due dates.


Oshefsky and her husband, Lucas, grew in more ways than one at Froedtert during the two weeks she stayed there before her delivery. She giggled as she recalled little moments like playing hours of board games and cribbage and watching Netflix in addition to some life-changing memories.


“[Lucas] was applying to go to Wisconsin Public Service to take a new position,” Oshefsky says. “We actually applied in Froedtert, and he ended up getting the job, so that was kind of cool.”


Both sisters also developed a close relationship with their team of doctors amid a lot of unknowns and nerves.


“Each time [we deliver with Froedtert], it’s gotten a little less nerve-wracking and scary … I mean it’s still childbirth and anything can happen, but it’s nice to know what we’re in for going [to Froedtert],” Thiem says. “A lot of times when I go down there, and my sister as well, we have a lot of the same nurses which is really fun to know someone who remembers your name. We’re not super familiar with the [Milwaukee] area, but it feels almost like home when we’re down there.”


Dr. Scott Cohen is the medical director of the adult congenial heart disease program at Children’s Wisconsin Hospital and co-medical director of the heart disease and pregnancy program at Froedtert Hospital. Photography by Children's Wisconsin.

Oshefsky says Cruz keeps up a strong relationship with her family and reaches out often.


Cruz says she values patient-provider communication, especially because her own father’s experience with heart conditions inspires her work every day.


“It’s super rewarding to work with patients like Cassi and Steffi because they come back to us with all of their future pregnancies, so you know they trust us, and it’s just super rewarding to be part of that journey with them — to be able to have children and keep them safe at the same time,” Cruz says.


Because Oshefsky and Thiem’s condition is genetic, Cohen says his team conducted fetal echocardiograms on each of their babies at around 20 weeks. Although bicuspid aortic valves are the most common type of congenital heart disease, he says they are extremely hard to catch before babies are born. 


Thiem says the moment she found out her son Cole had the same heart condition is one she will never forget. She felt connected with her mother who has supported the sisters every step of the way. 

“I’m happy I can be there for [Cole] because I’ve been through it all,” Thiem says. “I feel like I have a really special bond with him…knowing that we have the same thing.”

Miracle-like motherhood

Today, the sisters don’t just share a congenital heart defect, but they also share the experience of motherhood. Their first daughters entered this world two months apart, and each sister had two more children while Steffi awaits her fourth’s arrival.


Thiem says the sisters’ experience watching their children grow up together is indescribable. Even though they are perfectly healthy, their bond grows through a mutual understanding of what it is like to have anxieties about their hearts as they care for their children.


Thiem says she is eternally grateful for the doctors who helped her and Oshefsky get where they are today, as she cannot imagine her life without their beautiful, growing family. 


“It’s almost shocking that we’re having a fourth child, but we have so much trust in the doctors and the team at Froedtert,” Thiem says. “I’m not scared.”

Featured photo by Stacy DeGrave/Small Town Snapshots By Stacy.