Stories about: Heart Center

A tissue engineered heart ventricle for studying rhythm disorders, cardiomyopathy

a tissue engineered heart ventricle
(Luke MacQueen and Michael Rosnach/Harvard University)

While engineered heart tissues can replicate muscle contraction and electrical activity in a dish, many aspects of heart disease can only adequately be captured in 3D. In a report published online yesterday by Nature Biomedical Engineering, researchers describe a scale model of a heart ventricle, built to replicate the chamber’s architecture, physiology and contractions. Cardiac researchers at Boston Children’s Hospital think it could help them find treatments for congenital heart diseases.

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Hearts get a boost from mitochondrial transplantation

In this artistic rendering, mitochondria (enlarged at top left) are depicted inside heart muscle cells. Watch an animation about mitochondrial transplantation.

For decades, cardiac researcher James McCully, PhD, has been spellbound by the idea of using mitochondria, the “batteries” of the body’s cells, as a therapy to boost heart function. Finally, a clinical trial at Boston Children’s Hospital is bringing his vision — a therapy called mitochondrial transplantation — to life.

Mitochondria, small structures inside all of our cells, synthesize the essential energy that our cells need to function. In the field of cardiac surgery, a well-known condition called ischemia often damages mitochondria and its mitochondrial DNA inside the heart’s muscle cells, causing the heart to weaken and pump blood less efficiently. Ischemia, a condition of reduced or restricted blood flow, can be caused by congenital heart defects, coronary artery disease and cardiac arrest.

For the smallest and most vulnerable patients who are born with severe heart defects, a heart-lung bypass machine called extracorporeal membrane oxygenation (ECMO) can help restore blood flow and oxygenation to the heart. But even after blood flow has returned, the mitochondria and their DNA remain damaged.

“In the very young and the very old, especially, their hearts are not able to bounce back,” says McCully.

Ischemia can be fatal for the tiniest patients

After cardiac arrest, for instance, a child’s mortality rate jumps to above 40 percent because of ischemia’s effects on mitochondria. If a child’s heart is too weak to function without the support of ECMO, his or her risk of dying increases each additional day spent connected to the machine.

But what if healthy mitochondria could come to the rescue and replace the damaged ones?

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Trial shows chemotherapy is helping kids live with pulmonary vein stenosis

Magnification of pulmonary vein tissue showing signs of pulmonary vein stenosis (plump abnormal cells stained dark magenta).
Magnification of pulmonary vein tissue showing signs of pulmonary vein stenosis (plump abnormal cells stained dark magenta). Credit: Boston Children’s Hospital Department of Pathology

Pulmonary vein stenosis (PVS) is a rare disease in which abnormal cells build up inside the veins responsible for carrying oxygen-rich blood from the lungs to the heart. It restricts blood flow through these vessels, eventually sealing them off entirely if left untreated. Typically affecting young children, the most severe form of PVS progresses very quickly and can cause death within a matter of months after diagnosis.

Until recently, treatment options have been limited to keeping the pulmonary veins open through catheterization or surgery. Yet this approach only removes the cells but does nothing to prevent their regrowth. Now, a clinical trial shows that adding chemotherapy to a treatment regimen including catheterization and surgery can deter abnormal cellular growth and finally give children with PVS a chance to grow up.

Results of the trial, run by the Boston Children’s Hospital Pulmonary Vein Stenosis Program, were recently published in the Journal of Pediatrics.

“Through this approach, we’ve created the first-ever population of survivors who are living with severe PVS,” says Christina Ireland, RN, MS, FNP, who has managed enrolling patients in the trial and treating new patients since the trial ended. “We’ve changed this disease from an acute killer to a chronic, manageable condition.”

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Stick-on respiratory monitor allows early detection of breathing problems

Toddler wearing ExSpiron respiratory monitor
A mock-up of the ExSpiron monitoring a toddler’s breathing

Children can be at risk for compromised breathing after surgery or from conditions like asthma, congestive heart failure or sleep apnea. Opioid therapy and sedation for medical procedures can also depress breathing. Unless a child is sick enough to have a breathing tube, respiratory problems can be difficult to detect early. Yet early detection can mean the difference between life and death.

“There is currently no real-time objective measure,” says Viviane Nasr, MD, an anesthesiologist with Boston Children’s Hospital’s Division of Cardiac Anesthesia. “Instead, respiratory assessment relies on oximetry data, a late indicator of respiratory decline, and on subjective clinical assessment.”

A new device, recently cleared by the FDA for children 1 year and older in medical settings, provides an easy, noninvasive way to tell how much air the lungs are receiving in real time. It can signal problems as much as 15-30 minutes before standard pulse oximetry picks up low blood oxygenation, according to one study.

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Building a better bubble: Engineering tweaks bring safe IV oxygen delivery closer to reality

thin-shelled engineered oxygen bubbles
(Courtesy Yifeng Peng, Boston Children’s Hospital)

Everything from food aspiration to an asthma attack to heart failure can cause a patient to die from asphyxia, or lack of oxygen. For more than a decade, the Translational Research Laboratory (TRL) of Boston Children’s Hospital’s Heart Center has been pursuing a dream: tiny, oxygen-filled bubbles that can be safely injected directly into the blood, resuscitating patients who can’t breathe.

The lab’s first generation of bubbles were made with a fatty acid, but the lipid shells weren’t stable enough for long-term storage or clinical use. The bubbles popped open too easily.

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A “half-hearted” solution to one-sided heart failure

Illustration showing how the system supports a failing right ventricle
Illustration showing sectional view of a heart with the soft robotic system helping to draw blood into (left) and pump blood out (right) of the heart’s right ventricle.

Soft robotic actuators, which are pneumatic artificial muscles designed and programmed to perform lifelike motions, have recently emerged as an attractive alternative to more rigid components that have conventionally been used in biomedical devices. In fact, earlier this year, a Boston Children’s Hospital team revealed a proof-of-concept soft robotic sleeve that could support the function of a failing heart.

Despite this promising innovation, the team recognized that many pediatric heart patients have more one-sided congenital heart conditions. These patients are not experiencing failure of the entire heart — instead, congenital conditions have caused disease in either the heart’s right or left ventricle, but not both.

Read our Vector story on the soft robotic heart sleeve that mimics cardiac muscles.

“We set out to develop new technology that would help one diseased ventricle, when the patient is in isolated left or right heart failure, pull blood into the chamber and then effectively pump it into the circulatory system,” says Nikolay Vasilyev, MD, a researcher in cardiac surgery at Boston Children’s.

Now, Vasilyev and his collaborators — researchers from Boston Children’s, the Harvard John A. Paulson School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering at Harvard University — have revealed their soft robotic solution. They describe their system in a paper published online in Science Robotics today.

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Monitoring mitochondria: Laser device tells whether oxygen is sufficient

Shining a laser-based device on a tissue or organ may someday allow doctors to assess whether it’s getting enough oxygen, a team reports today in the journal Science Translational Medicine.

Placed near the heart, the device can potentially predict life-threatening cardiac arrest in critically ill heart patients, according to tests in animal models. The technology was developed through a collaboration between Boston Children’s Hospital and device maker Pendar Technologies (Cambridge, Mass.).

“With current technologies, we cannot predict when a patient’s heart will stop,” says John Kheir, MD, of Boston Children’s Heart Center, who co-led the study. “We can examine heart function on the echocardiogram and measure blood pressure, but until the last second, the heart can compensate quite well for low oxygen conditions. Once cardiac arrest occurs, its consequences can be life-long, even when patients recover.”

In critically ill patients with compromised circulation or breathing, oxygen delivery is often impaired. The new device measures, in real time, whether enough oxygen is reaching the mitochondria, the organelles that provide cells with energy.

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Can we improve neuropsychiatric outcomes in children with congenital heart disease?

Jane Newburger studies neurodevelopment in children with congenital heart defects
Jane Newburger, MD, has dedicated her career to helping children with heart defects reach their full potential.

About 1 out of 100 babies are born with a congenital heart defects. Thanks to medical and surgical advances, these children usually survive into adulthood, but they are often left with developmental, behavioral or learning challenges.

Children with “single-ventricle” defects — in which one of the heart’s two pumping chambers is too small or weak to function properly — are especially at risk for neurodevelopmental problems. “Single-ventricle physiology creates cerebrovascular hemodynamics that can reduce oxygen delivery to the brain,” explains Jane Newburger, MD, MPH, director of the Cardiac Neurodevelopmental Program at Boston Children’s Hospital.

How does this play out in adolescence? In three recent studies, Boston Children’s Heart Center collaborated with the departments of Neurology and Psychiatry to track neurodevelopmental outcomes after corrective Fontan operations. They evaluated preteens and teens as old as 19 — the longest follow-up to date.

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Preparing patients and families to manage ventricular assist devices

Beth Hawkins ventricular assist devices

Children in severe heart failure sometimes have a ventricular assist device (VAD) implanted in their chest. VADs are electrically-powered heart pumps that can tide children over while they wait for a heart transplant. They can also be implanted long term if a child is ineligible for transplant, or simply buy children time to recover their own heart function.

Because problems with VADs can be life-threatening, families need extensive training in managing the device and its external controller at home. Nurse practitioner Beth Hawkins RN, MSN, FNP-C, and her colleagues in the Boston Children’s VAD Program begin the training at the child’s hospital bedside while they are still in the cardiac ICU. But despite lectures, demos and practice opportunities, the prospect of maintaining a VAD remains terrifying for many parents and children.

“A lot of families feel their child is attached to a ticking time bomb that could go off at any time,” says Hawkins. “Many say taking a child home on a VAD feels like having a newborn baby again.”

Hawkins realized that families needed more support.

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Soft robot could aid failing hearts by mimicking healthy cardiac muscle

heart-failure

Every year, about 2,100 people receive heart transplants in the U.S., while 5.7 million suffer from heart failure. Given the scarcity of available donor hearts, clinicians and biomedical engineers from Boston Children’s Hospital and Harvard University have spent several years developing a mechanical alternative.

Their proof of concept is reported today in Science Translational Medicine: a soft robotic sleeve that is fitted around the heart, where it twists and compresses the heart’s chambers just like healthy cardiac muscle would do.

Heart failure occurs when one or both of the heart’s ventricles can no longer collect or pump blood effectively. Ventricular assist devices (VADs) are already used to sustain end-stage heart failure patients awaiting transplant, replacing the work of the ventricles through tubes that take blood out of the heart, send it through pumps or rotors and power it back into a patient’s bloodstream. But while VADs extend lives, they can cause complications.

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