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The Last Option
Evan M. Zahn, MD, discusses performing an unconventional interventional procedure to save the life of a premature newborn.
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At just 5 lb and more than 2 months premature, there were already quite a number of reasons to be concerned when Audrey Boughamer was born. But factor in a patent ductus arteriosus, and the already complicated scenario became exponentially more dire.
“I would say if left untreated, her chances of survival and recovery were quite small,” Evan M. Zahn, MD, director of the congenital heart program at the Heart Institute and department of pediatrics at Cedars-Sinai, Los Angeles, said in an interview with Cardiology Today’s Intervention.
Failing medical therapy and too sick for surgery, there was only one treatment option available, according to Zahn.
Evan M. Zahn
“I have been recently collaborating with a colleague in Oxford, England, and he’s been doing some pioneering work with closing these kinds of communications in tiny newborns,” Zahn said. “So after speaking with him and seeing how sick this baby was and having no other good options, we approached the parents about closing the patent ductus arteriosus (PDA) at the bedside with an FDA-approved percutaneous device [Amplatzer Vascular Plug II, AGA Medical].”
However, traditionally, the smallest size infant who would receive the procedure is 10 lb, roughly twice the size of Audrey, Zahn said.
“I was cautiously optimistic that we could help her, but quite nervous that we could also hurt her,” he said. “Of all the cases I’ve done, this one probably had the least margin of error. Everything had to be perfect.”
No Other Alternative
Eighteen days before the procedure, Audrey was born on March 11, 2013, at a hospital in Santa Barbara. At only 5.3 lb and roughly 2.5 months premature, her PDA was 3.5 mm, a moderate size for a child, but very large for a premature newborn. She also had chronic pulmonary effusions that required draining and low BP. Because of these mounting health concerns, she was flown to Cedars-Sinai, nearly 90 miles away.
“The ideal way we like to treat her condition is with medication. She was on inotropic medicine to support her low BP — epinephrine and dopamine and had received indomethacin — which can close the PDA, but it had no effect,” Zahn said. “The next option is surgery, but it was thought that the baby would not tolerate it because she was simply too sick.”
This left only one option: closing the PDA with a catheter-based approach.
“We have been closing PDAs without surgery in larger kids and adults for close to 25 years, and there’s all kinds of different ways to do this; unfortunately, at this time, these procedures generally involve relatively stiff catheters and need to be performed in a cath lab,” Zahn said. “However, the smallest patients are generally at least twice the size of Audrey, and we didn’t think she would tolerate being moved to a cath lab. She was just too small.”
Figure 1. Two-dimensional echocardiogram with (right panel) and without color Doppler taken from a high parasternal view, demonstrating a moderate-sized patent ductus arteriosus with left-to-right shunting across it.
Images: Evan M. Zahn, MD
Navigating a ‘Cocktail Straw’-Sized Femoral
With the infant still in neonatal ICU and in an incubator, Zahn began the process of percutaneously closing the PDA by accessing the femoral artery, which was the first challenge in a procedure of this nature.
“The femoral artery in a baby her size was no bigger than a cocktail straw, probably smaller,” he said. “So I had to get a needle perfectly positioned and then get a very thin, 0.014-inch guidewire inserted into the vessel, followed by the catheter, all without destroying the femoral artery.”
Adding to the complexity, there was no fluoroscopy available in the neonatal ICU, necessitating the use of echocardiographic guidance instead, which would never be used in this situation under normal circumstances, according to Zahn.
“Because the PDA was so large, once we crossed it, the catheter fell into it; we couldn’t stay out of it,” he said.
Once inside the pulmonary artery, Zahn and colleagues sized the device and chose a 4-mm vascular plug.
“One of the biggest concerns I had during the procedure was the placement of the device,” Zahn said. “If I placed the device just a millimeter favoring one side, it would have stuck into the pulmonary artery and blocked one of the lung arteries. If I placed it a millimeter favoring the other side, it would have blocked the aorta. So we had to get it positioned just perfectly, so that when we closed the PDA there would be no obstruction to flow.”
Once satisfied with the placement on his second attempt, what came next was the most harrowing part of the procedure, Zahn said. Not only was this the first time working in such small anatomy, but there was also the concern that the baby’s tissue might be too soft and delicate to hold the plug in place following deployment.
“One nightmare scenario for us would have been as I released the device, it migrated to some place that would have been very difficult to retrieve it from, either the aorta or pulmonary artery, both of which would have been catastrophic,” Zahn said. “Much to our delight, when we deployed the plug, it fit nicely into place and did not cause any trouble.”
Figure 2. Following device closure, the occluder can be seen in place across the patent ductus arteriosus with no evidence of residual flow by color Doppler imaging.
Immediate and Gradual Improvements
Shortly after closing the vessel, which took about 15 minutes, Zahn noticed that Audrey’s BP had improved. Within a week, she was completely off inotropic medication.
“However, lung disease takes quite a bit longer to recover from. Since she was so drastically ill, it took almost a month to get her back to baseline. But we were able to get her back to and eventually off a regular ventilator,” he said. “I have little doubt that this procedure helped her turn the corner.”
In fact, 2 months after the procedure, Audrey was transferred to a less acute nursery where her family lives in Santa Barbara.
“She still has a fair amount of recovery left, but she is now in a crib,” Zahn said. “She has an IV in place and is getting a little oxygen by nose as her lungs recover. Importantly, she is beginning to eat, which is always a big deal for babies when they are born so prematurely. The ultimate hope is that she will be going home soon.”
Into the Record Books?
Although he’s uncertain whether this procedure qualifies as a national record for the youngest/smallest patient to undergo transcatheter PDA closure in the United States, Zahn said he is fairly confident that it has no precedent in the country.
“I’ve performed a literature search and there are only two papers published on treating tiny babies with this technique: one from Canada and one from Britain. Both of them have one or two babies the size of Audrey in it, but there is nothing from the United States,” he said. “So I’m fairly certain this is unique to the United States, and I’d say around the world this is among the smallest babies to undergo this treatment.”
But, more important than records, Zahn sees the potential for the application of this procedure in more tiny newborns with PDAs.
“We think with some further modifications, this technique may be applicable to premature babies down to 700 g to 800 g, providing our neonatology colleagues with another important tool for improving the survival outlook of extremely premature babies,” he said. “We are currently formulating a procedure that would utilize a combination of fluoroscopy and echocardiography to treat these babies from a transvenous approach at the bedside, thereby avoiding the risks associated with arterial catheterization and increasing the range of babies that can undergo this therapy.” – by Brian Ellis
Disclosure: Zahn reports no relevant financial disclosures.