The Heart Center team at University of Minnesota Masonic Children’s Hospital offers hope to parents of premature infants diagnosed with patent ductus arteriosus, thanks to its adoption of leading-edge devices and new minimally invasive procedures.
Patent ductus arteriosus (PDA), a heart condition in which the ductus arteriosus fails to close after birth, affects up to 20% of premature infants and poses significant health threats to these tiniest and most fragile patients. While treatments for the condition have evolved, surgical options for premature infants have been limited to incisions and surgical ligation — until now. University of Minnesota Masonic Children’s Hospital’s Heart Center and pediatric interventional cardiologist Gurumurthy Hiremath, MD, have led area efforts in investigating the use of new occlusion devices and minimally invasive procedures in these young patients, with promising results.
Premature Infants and PDA
Connecting the aorta to the pulmonary artery, the ductus arteriosus allows the fetus to receive blood oxygenized by the placenta, bypassing the fetus’ as yet undeveloped lungs. The ductus arteriosus typically closes in infants within hours or days of their being born. If the artery does not seal itself and remains patent (or open), it is referred to as PDA.
PDA sends extra blood to the lungs, as there is nothing to stop blood flow from the aorta to the pulmonary arteries through the ductus arteriosus. As a result, the lungs can become congested, which forces the heart and lungs to work harder. The condition can lead to worsening lung disease, pulmonary hypertension, rapid pulse and reduced heart function. Health complications stemming from these issues depend on multiple factors, including the size of the PDA and overall health of the child.
If the PDA is small, the only symptom may be a minor heart murmur. However, if the PDA is large, more severe symptoms can occur, such as fast breathing, shortness of breath, poor growth and permanent damage to blood vessels in the lungs. These symptoms can be particularly dangerous for infants who are born prematurely.
“Premature infants, born with small, immature lungs, already have a lot of breathing problems, which is why they typically need respiratory support in the NICU,” says Gurumurthy Hiremath, MD, FACC, FSCAI, Director of Pediatric Interventional Cardiology at University of Minnesota Masonic Children’s Hospital. “PDA makes it even more difficult for them to breathe, because it causes extra blood to be sent to the lungs.”
The extra flow of blood to the lungs also prevents much-needed blood from reaching the stomach, which can cause feeding problems for premature infants in addition to respiratory issues. Unfortunately, premature infants are more likely to have PDA than infants born at full term. “Approximately 60,000 infants are born prematurely in the United States every year,” Dr. Hiremath says. “Nearly one in five of them — about 12,000 infants — will have a PDA that requires treatment.”
In children who are born at full term, the PDA may be allowed to close naturally over time if symptoms are not severe. In premature infants, however, there is a greater chance that symptoms and severity of the PDA will necessitate treatment. “The more preterm a child is, the higher likelihood that the PDA will not close on its own,” Dr. Hiremath says.
If treatment is required, medications such as ibuprofen or indomethacin are used in a first attempt to seal the PDA for both preterm and full-term infants.
“In most cases, these medicines do not work, and up until about a year or two ago, we would have to resort to surgery to close a PDA in a premature infant,” Dr. Hiremath says. “But performing surgery on a baby who weighs approximately two pounds is challenging.”
A Difficult Surgery
In full-term infants, PDAs can be closed through a minimally invasive procedure and placement of a transcatheter device. The device is inserted via catheter through a blood vessel in the groin and is threaded to the heart and site of the PDA, where the interventional cardiologist can deploy the device and block the PDA.
Until recently, however, device size and technology were not suitable to smaller premature infants. Closing PDAs in premature infants required surgical ligation and a procedure that accessed the heart through a large incision in the infant’s chest. During the procedure, the PDA is tied off with a suture or permanently closed with a miniature metal clip that squeezes the PDA shut.
Performing open surgery on a child so young and small carries a high risk of complications, as the procedure can exacerbate breathing symptoms in the short term and poses a risk for infection and injury.
This surgical procedure has remained the standard care approach for addressing PDA in premature infants. However, clinical trials of minimally invasive procedures with microcatheters and the approval of devices suitable for addressing PDA in premature infants are presenting new options. At University of Minnesota Masonic Children’s Hospital, Dr. Hiremath began using a system originally designed for addressing vascular defects in adults — the Medtronic MVP micro vascular plug system — to block PDAs.
“Until now, we did not have the technology to close the PDA through the leg vein in small, premature babies,” Dr. Hiremath says. “So, we began using a device that was approved by the FDA for a different indication.”
With the FDA approval of the Abbott Amplatzer Piccolo Occluder — a device specifically designed to treat PDA in premature infants — in January, he added a second device to the transcatheter treatment options for premature infants with PDA.
“Our outcomes have been remarkable with this approach,” Dr. Hiremath says. “All 21 of our patients have had no complications so far. Once you close the PDA, there is a marked difference in ease of breathing, and we can start to make progress on weaning infants from respiratory support. They can usually go home sooner with these procedures.”
“University of Minnesota Masonic Children’s Hospital was the first in the state to offer transcatheter closure for PDA in premature infants and the first to use an FDA-approved device indicated for this condition. We have been a local pioneer for these procedures, and we want to make community neonatologists aware that transcatheter closure is an option for these patients — which means surgery on this fragile patient population would not be necessary.”
— Gurumurthy Hiremath, MD, FACC, FSCAI, Director of Pediatric Interventional Cardiology at University of Minnesota Masonic Children’s Hospital
Getting the Right Fit
Of the 21 transcatheter PDA closures Dr. Hiremath and the Heart Center team at University of Minnesota Masonic Children’s Hospital performed on premature infants in the past two years, the first 15 employed the MVP, which comes in various multimillimeter sizes for proper fit and placement.
Since the FDA approval of the Abbott Amplatzer Piccolo Occluder, Dr. Hiremath has successfully used it to close six PDAs in premature infants.
The transcatheter PDA closure procedures take about a half an hour to perform, from initial incision to the location and sizing of the PDA, placement of the occlusion device and confirmation that the device is sitting tightly and not obstructing other blood vessels. The use of echocardiograms helps interventional cardiologists guide the catheter and place devices.
“Echocardiographers are vital to the success of the procedure,” Dr. Hiremath says.
University of Minnesota Masonic Children’s Hospital was the first institution in the state to begin offering the MVP and Piccolo Occluder for the closure of PDAs in premature infants.
“These are amazing procedures that require no cutting, incisions or dressings,” Dr. Hiremath says. “There really is no recovery time, which makes things easy and simple for us, our patients and their families.”
It Takes a Village
Dr. Hiremath works closely with neonatologists both inside and outside of University of Minnesota Health locations in treating PDA in premature infants. He sees patients referred from hospitals in St. Cloud, Maple Grove, Fargo and elsewhere in the region.
“Without the help of neonatologists, these procedures would not be possible,” Dr. Hiremath says. “We want open communication with outside referring neonatologists and pediatric cardiologists.”
He reviews PDA cases with the University of Minnesota Masonic Children’s Hospital NICU on a weekly basis to ensure all specialists are fully informed about that week’s procedures.
“Neonatologists, pediatric cardiologists, sonographers, echocardiographers, echo technicians, anesthesiologists and our surgeons — who are on standby in case surgery is required — all come together to make these procedures happen,” Dr. Hiremath says.
Dr. Hiremath and University of Minnesota Health pediatric heart care specialists have also been engaged in educational talks and worked to provide opportunities for area physicians to learn more about catheterization procedures in the treatment of PDAs in premature infants.
“We’re working diligently to make more people aware,” Dr. Hiremath says. “We want to be able to help every infant who can benefit from this procedure.”
For 24/7 neonatal transport or consultation with a physician at the University of Minnesota Masonic Children’s Hospital NICU, call 612-273-7600.