Pediatric Cardiology: Congenital and Acquired Heart Disease

Pediatric cardiology is the medical specialty focused on diagnosing and treating heart conditions in children, from the fetal period through adolescence. It covers an enormous range of problems, from tiny holes between heart chambers that close on their own to complex structural malformations requiring multiple open-heart surgeries before a child’s first birthday. Congenital heart defects are the most common type of birth defect worldwide, affecting roughly 9 out of every 1,000 live births in recent decades, and the field has transformed what were once uniformly fatal conditions into survivable, manageable ones.

How Common Are Heart Defects in Children

Congenital heart disease is far more prevalent than most people realize. A systematic review covering over 130 million live births across 260 studies found that birth prevalence rose progressively over the decades, reaching about 9.4 per 1,000 births in the period from 2010 to 2017.¹ That does not necessarily mean more babies are being born with heart defects than in earlier eras. Better imaging, routine screening, and broader diagnostic criteria have increased detection rates. An earlier meta-analysis of over 24 million births reported that the observed rate climbed from about 0.6 per 1,000 live births in the early 1930s to roughly 9.1 per 1,000 after 1995, then stabilized, corresponding to an estimated 1.35 million newborns with congenital heart disease annually worldwide.²

Geography matters. Asia consistently reports the highest birth prevalence, around 9.3 per 1,000, while Africa reports the lowest, around 2.3 per 1,000.³ Those African figures almost certainly reflect underdiagnosis rather than genuinely lower disease rates, since echocardiography access and newborn screening programs remain limited in many low-income settings. In Europe, reported rates are higher than in North America (about 8.2 versus 6.9 per 1,000), a gap that may partly reflect differences in screening practices and case definitions.⁴ Globally, an estimated 12 million people were living with congenital heart disease in 2017, an increase of nearly 19% from 1990, driven primarily by improved survival and population growth.⁵

What Causes Congenital Heart Disease

The short answer is that most congenital heart defects have a genetic component, but pinpointing the exact cause in a given child remains surprisingly difficult. Genetic factors are estimated to contribute to about 90% of cases, yet a molecular diagnosis cannot be identified in up to 55% of patients.⁶ Chromosomal abnormalities and copy number variations, where chunks of DNA are deleted or duplicated, account for roughly 23% of cases overall. The rest involve a tangled mix of single-gene mutations, small-scale genetic changes, and environmental exposures like maternal diabetes, certain medications, and infections during pregnancy. For many families, the frustrating reality is that no single clear-cut cause can be found. The heart forms during the first eight weeks of pregnancy through a tightly choreographed sequence of folding, looping, and septation, and even small disruptions in this process can produce structural defects.

Prenatal Detection and Why It Matters

One of the most consequential advances in pediatric cardiology has been the ability to diagnose heart defects before birth. Fetal echocardiography, essentially an ultrasound focused on the baby’s heart, can identify many major structural abnormalities during the second trimester. The practical value of early diagnosis is hard to overstate. When a serious heart defect is known ahead of delivery, the birth can be planned at a center with a pediatric cardiac surgery team, medications can be started immediately, and the baby avoids the dangerous period of deterioration that can occur when a critical defect goes unrecognized.

Fetal echocardiography can also help doctors stratify risk. Research has shown that fetuses assigned higher levels of concern based on prenatal imaging have significantly greater rates of critical illness after birth, higher need for surgical or catheter-based intervention, and higher hospital mortality.⁷ The consequences of missed prenatal diagnosis can be severe. In one study of neonates with critical heart defects, babies diagnosed only after birth had a transfer mortality rate of about 6%, with some arriving dead or in cardiac arrest because of the unplanned transport.⁸ Those deaths are largely preventable with prenatal identification.

The Spectrum of Structural Defects

Congenital heart defects range widely in severity. The mildest, such as small ventricular septal defects (holes between the lower chambers), often cause no symptoms and close on their own. At the other extreme are conditions like hypoplastic left heart syndrome, in which the left side of the heart is so underdeveloped that it cannot support the body’s circulation at all.

When holes between chambers are large and left unrepaired, blood shunts from the high-pressure left side to the lower-pressure right side and floods the lungs with excess flow. Over time, this damages the blood vessels in the lungs and raises pulmonary pressure. Small-to-moderate ventricular septal defects lead to irreversible lung damage, known as Eisenmenger syndrome, in only about 3% of cases, but larger defects almost always progress to it if no intervention is performed.⁹ Eventually, the shunt reverses direction, sending oxygen-poor blood into the body and causing cyanosis, the bluish discoloration of the skin and lips. At that stage, the lung damage is generally irreversible and the patient’s options narrow dramatically.¹⁰

Tetralogy of Fallot is the most common cyanotic congenital heart defect, making up roughly 3 to 5% of all congenital heart disease. It involves four anatomical features: a ventricular septal defect, narrowing of the outflow from the right ventricle to the lungs, thickening of the right ventricle, and an aorta that straddles the septal defect. Infants with this condition can experience sudden episodes of deep cyanosis, sometimes called “tet spells,” typically between two and four months of age, triggered by drops in body resistance or spasms in the outflow tract that further restrict blood flow to the lungs.¹¹

Staged Surgical Palliation for Single-Ventricle Hearts

Hypoplastic left heart syndrome was universally fatal just four decades ago. Today, it is managed through a three-stage series of surgeries that reroute the circulation so the single functional ventricle does the work that two ventricles normally share. The first operation, the Norwood procedure, is performed in the first days of life and remains one of the highest-risk and costliest common operations in congenital heart surgery.¹² The second and third stages, performed months to years later, gradually redirect venous blood directly to the lungs, bypassing the right side of the heart entirely and culminating in the Fontan circulation.¹³

The Fontan circulation keeps patients alive, but it comes with its own long-term consequences. Without a pumping chamber driving blood through the lungs, venous pressure stays chronically elevated. Virtually all Fontan patients develop some degree of liver congestion, which leads to a distinctive form of progressive liver disease, often beginning in childhood and advancing to fibrosis and cirrhosis.¹⁴ Managing these patients means lifelong monitoring of not just the heart but the liver, kidneys, and other organs affected by the abnormal circulatory pattern.

Acquired Heart Disease in Children

Not all pediatric heart disease is present at birth. Several conditions can damage a previously healthy child’s heart, and pediatric cardiologists are closely involved in their management.

Kawasaki Disease

Kawasaki disease is an inflammatory illness that primarily strikes children under five. Its most feared complication is the development of coronary artery aneurysms, which can lead to heart attacks even in toddlers. Treatment with high-dose intravenous immunoglobulin (IVIG) has been the standard of care for decades and dramatically reduces aneurysm risk. A meta-analysis found that children receiving a single high-dose IVIG infusion had a coronary aneurysm rate of only about 2% at 30 days, compared with roughly 23% in children treated with aspirin alone.¹⁵ Among children who do develop aneurysms, those treated with IVIG plus additional anti-inflammatory therapy have shown aneurysm regression rates as high as 91%, compared with 68% in other treatment combinations.¹⁶

The role of high-dose aspirin alongside IVIG has recently been questioned. A randomized trial found that giving IVIG alone, without the traditional high-dose aspirin regimen, did not increase the risk of coronary artery lesions. The study concluded that the addition of high-dose aspirin during initial IVIG treatment was neither statistically significant nor clinically meaningful in preventing coronary damage.¹⁷ This finding may eventually shift practice away from the high-dose aspirin that has been part of Kawasaki protocols for years.

Rheumatic Heart Disease

Rheumatic fever remains a major cause of acquired heart disease in low- and middle-income countries. It occurs when the immune system, responding to a group A streptococcal throat infection, mistakenly attacks the body’s own tissues through a process called molecular mimicry: antibodies directed at streptococcal proteins cross-react with proteins in the heart valves.¹⁸ Research has identified a specific streptococcal sugar molecule that triggers antibodies capable of binding to heart valve tissue and the basement membrane beneath it, setting off inflammation that can permanently scar the valves.¹⁹ Repeated bouts of rheumatic fever progressively worsen the damage, which is why secondary prevention with long-term penicillin prophylaxis is so important. In wealthier nations, routine antibiotic treatment of strep throat has made rheumatic heart disease rare, but globally it still affects tens of millions of people.

Multisystem Inflammatory Syndrome in Children

The COVID-19 pandemic brought a new condition into pediatric cardiology clinics. Multisystem inflammatory syndrome in children (MIS-C) emerged as a post-infectious inflammatory response that can severely affect the heart. Studies have shown that up to about 80% of children with MIS-C have some form of cardiac involvement, ranging from reduced heart-pumping function and coronary artery dilation to electrical rhythm disturbances.²⁰ An Italian single-center study found cardiac manifestations in 81% of its MIS-C patients, including valve leakage, coronary artery changes, and conduction abnormalities.²¹ The good news is that most children recover cardiac function with treatment, though some require ongoing monitoring for lingering effects.

Catheter-Based Treatments

Not every heart problem in a child requires open surgery. Interventional catheterization has expanded the range of conditions that can be treated by threading devices through blood vessels to the heart. One of the most notable developments has been transcatheter pulmonary valve replacement, which allows doctors to implant a new valve inside a failing right ventricular outflow tract conduit without cracking the chest open. This approach is now widely accepted as an alternative to repeat surgery for patients whose surgically placed conduits have deteriorated, though it is not yet suitable for every anatomy.²²

Even small children can undergo these procedures. A multicenter study evaluated transcatheter pulmonary valve implantation in 25 patients weighing under 30 kilograms, with some weighing under 20 kilograms. After implantation, the peak pressure gradient across the conduit dropped from an average of 29 to 9 mmHg, and nearly all patients went from significant valve leakage to none or trivial amounts.²³ Longer-term data on the Melody valve, one of the most commonly used devices, has shown good hemodynamic and clinical outcomes up to seven years after implantation, with true valve failure being rare. Stent fracture was the main cause of dysfunction early on, but that problem became uncommon once doctors began routinely placing a reinforcing stent before the valve.²⁴

Heart Failure, Mechanical Support, and Transplant

When a child’s heart muscle fails beyond what medical therapy or surgery can fix, the remaining options are mechanical circulatory support and transplantation. Ventricular assist devices (VADs) are mechanical pumps that help the weakened heart move blood. In children, they serve primarily as a bridge to transplant, keeping the child alive while waiting for a donor heart. A multi-institutional study found that 77% of children placed on a VAD survived to transplant, and 5% recovered enough heart function to have the device removed entirely. In the most recent era of the study, the transplant bridge rate reached 86%.²⁵

The underlying diagnosis matters a great deal. Children with cardiomyopathy, a disease of the heart muscle itself, reached transplant 84% of the time with a waitlist mortality of 9%. For children with congenital heart disease, the numbers were worse: only 55% bridged to transplant, with a 36% waitlist mortality.²⁶ The complex anatomy of congenital heart disease makes VAD placement technically harder, and these patients often have additional complications. Encouragingly, once children on VAD support do reach transplant, their post-transplant outcomes are comparable to those of children who waited on medical therapy alone, suggesting that the device effectively resets the playing field despite these patients being sicker going in.²⁷

ECMO as an Emergency Rescue

Extracorporeal membrane oxygenation (ECMO) is the most aggressive form of temporary life support available. It takes over the work of both the heart and lungs by pumping blood through an external oxygenator. In pediatric cardiac patients, ECMO is sometimes deployed during cardiac arrest that does not respond to standard resuscitation, a scenario called extracorporeal cardiopulmonary resuscitation, or ECPR. A large review found that ECMO used to support CPR rescued roughly one-third of pediatric patients who would otherwise have certainly died.²⁸ Another study of 80 children requiring emergency ECMO during refractory cardiac arrest reported that 54% were successfully weaned off the machine, though only 34% survived to hospital discharge, reflecting the extreme severity of the situations in which ECMO is used.²⁹

Neurodevelopmental Outcomes After Heart Surgery

Saving a child’s life is the first goal, but pediatric cardiologists increasingly recognize that survival alone is not enough. Children who undergo open-heart surgery in infancy are at elevated risk for developmental delays affecting motor skills, language, learning, and behavior. A scientific statement from the American Heart Association identifies multiple layers of risk, including genetic predisposition, fetal and perinatal brain injury, surgical and perioperative factors, socioeconomic disadvantage, and parental psychological distress.³⁰

The encouraging trend is that outcomes are improving over time. A large analysis of developmental testing in infants after cardiac surgery found that both motor and mental development scores improved by about 0.4 points per calendar year after adjusting for patient factors such as birth weight, sex, maternal education, and the presence of a genetic condition.³¹ That gradual improvement likely reflects a combination of better surgical and anesthetic techniques, more protective brain strategies during bypass, and earlier recognition and intervention for developmental concerns. Factors like prolonged mechanical ventilation, longer intensive care stays, and the presence of a genetic syndrome remain strong predictors of worse developmental outcomes across settings.³²

Exercise Capacity and Daily Life

Parents often wonder how much physical activity their child can handle after a heart defect is diagnosed or repaired. The general picture is that children with congenital heart disease have measurably lower exercise capacity than healthy peers. A meta-analysis found that children and adolescents with congenital heart disease had peak oxygen consumption about 8 ml/kg/min lower than controls, a meaningful gap that corresponds to reduced stamina during sports and vigorous play.³³ The degree of limitation varies enormously depending on the type and severity of the defect and the success of repair. Many children with repaired simple lesions lead fully active lives, while those with single-ventricle circulations or significant residual disease face more substantial restrictions. Importantly, physical activity is generally encouraged rather than avoided. Deconditioning from excessive restriction can be as harmful as the underlying defect, and exercise testing helps cardiologists tailor individualized activity recommendations.

The Dropout Problem in Adolescence

Perhaps the most underappreciated challenge in pediatric cardiology is the transition from pediatric to adult care. As patients reach their teenage years and early adulthood, a striking number simply stop seeing a cardiologist. One study found that failure to receive any cardiac follow-up after the sixth, thirteenth, and eighteenth birthdays occurred in 28%, 47%, and 61% of patients, respectively. Even among those with severe lesions, only 79% were seen after turning eighteen.³⁴ The consequences can be serious. Adults with repaired or palliated congenital heart disease often require ongoing surveillance for arrhythmias, valve deterioration, heart failure, and the systemic complications described in the Fontan population. Falling out of care during the very years when these issues begin to emerge means that problems are caught late, sometimes after irreversible damage has occurred. Structured transition programs, adult congenital heart disease clinics, and patient education are all areas of active development aimed at closing this gap.

Rhythm Disorders in Children

Heart rhythm problems are another domain within pediatric cardiology. In fetuses and newborns, the most common type of rapid heart rhythm is a form of supraventricular tachycardia caused by an extra electrical connection between the upper and lower chambers. This accounts for an estimated 60 to 90% of fetal supraventricular tachycardia cases, with heart rates typically between 220 and 300 beats per minute.³⁵ In older children, these accessory pathways can cause Wolff-Parkinson-White syndrome, which is treatable and often curable with catheter ablation. Children with congenital heart disease are also at higher risk for rhythm disturbances, both as a direct consequence of their anatomy and as a result of surgical scar tissue. Advances in imaging and 3D mapping have improved catheter ablation success rates in pediatric patients, even those with complex post-surgical anatomy.

Global Disparities in Pediatric Cardiac Care

Congenital heart disease is a leading cause of infant mortality worldwide, and the gap between wealthy and resource-limited countries remains stark.³⁶ In high-income countries, over 90% of babies born with congenital heart disease survive to adulthood. In low- and middle-income countries, many children with treatable defects die without ever being diagnosed, let alone operated on. The barriers are layered: too few trained surgeons, too few equipped centers, delayed referral from rural areas, inadequate intensive care after surgery, and the financial burden on families. International partnerships and training programs have begun to establish pediatric cardiac surgery capacity in post-conflict and low-resource regions, but scaling these efforts to match the global burden of disease remains one of the field’s most pressing challenges.