Living with “half a heart” might seem impossible, yet it describes the reality for many born with complex congenital heart defects. This refers to conditions where one of the heart’s two main pumping chambers, or ventricles, is severely underdeveloped or functionally absent. Hypoplastic Left Heart Syndrome (HLHS) is a common example, where the left side of the heart is significantly smaller and less functional. Despite this profound challenge, medical advancements have transformed the outlook, making survival and a meaningful life possible for many.
Understanding Single Ventricle Hearts
The human heart normally has four chambers, including two powerful lower ventricles. The right ventricle pumps blood to the lungs, while the left ventricle pumps oxygen-rich blood to the rest of the body. In a single ventricle heart, only one of these ventricles functions effectively, meaning it must manage the entire circulatory workload. Conditions like Hypoplastic Left Heart Syndrome (HLHS), tricuspid atresia, or double inlet left ventricle all fall under this umbrella.
In HLHS, the left side of the heart—its ventricle, valves, and aorta—is underdeveloped. This prevents it from effectively pumping oxygenated blood to the body. To compensate, the heart relies on temporary connections present during fetal development, such as the patent ductus arteriosus and the foramen ovale, to maintain blood flow. The right ventricle, which would normally only supply blood to the lungs, is forced to pump blood to both the lungs and the body. This leads to mixed blood (oxygen-rich and oxygen-poor) circulating, causing symptoms like a bluish tint (cyanosis), rapid breathing, and feeding difficulties shortly after birth.
Surgical Pathways to Survival
Survival for those with single ventricle hearts involves a series of staged surgical procedures. This approach aims to re-route blood flow and establish a functional circulation despite having only one effective pumping chamber. The first stage, known as the Norwood procedure, is performed within the first few weeks of life. During this operation, surgeons reconstruct the aorta and connect it to the right ventricle, making it the primary pump for systemic circulation. A shunt is also placed to ensure adequate blood flow to the lungs.
The second stage, the Glenn procedure, usually occurs when the child is between four and six months old. This surgery involves connecting the superior vena cava, which carries oxygen-poor blood from the upper body, directly to the pulmonary artery. This allows upper body blood to flow passively to the lungs, reducing the single ventricle’s workload, and the initial Norwood shunt is removed.
The final stage, the Fontan procedure, is performed between 18 months and three years of age. In this operation, the inferior vena cava, carrying oxygen-poor blood from the lower body, connects directly to the pulmonary artery, often via a conduit. After the Fontan procedure, all oxygen-poor blood flows passively to the lungs, bypassing the heart’s pumping chamber. This allows the single ventricle to concentrate its effort on pumping only oxygen-rich blood to the rest of the body. Medications support these stages, for instance, by keeping certain fetal connections open until surgery.
Daily Life with a Complex Heart
Those who have undergone these surgical corrections can lead active and fulfilling lives. However, living with a single ventricle heart necessitates ongoing medical management and an understanding of limitations. Regular medical check-ups with a cardiologist are essential, often including echocardiograms and stress tests, to monitor heart function and health.
While many patients maintain good activity levels, their exercise capacity is often reduced compared to healthy individuals. They may experience fatigue, shortness of breath, or reduced endurance, especially during strenuous physical activity. Avoiding dehydration and extreme exertion is advised to minimize stress on the cardiovascular system. Patients might also experience symptoms such as swelling (edema) or abnormal heart rhythms, which require careful monitoring and management. Lifelong medications are common to support heart function, manage symptoms, and prevent complications.
The Future for Patients
Lifelong specialized cardiac care is necessary for those with single ventricle hearts. While the staged surgical approach improves survival, it does not create a normal heart, and patients may face various long-term complications. These can include heart failure, which may appear years after the Fontan procedure. Abnormal heart rhythms (arrhythmias) are common and can impact health, sometimes requiring intervention.
Many Fontan patients also develop Fontan-associated liver disease (FALD), where chronic congestion leads to liver fibrosis and, in some cases, cirrhosis. Another complication is protein-losing enteropathy (PLE), where proteins leak from the intestines, causing swelling and nutrient malabsorption. Blood clots (thromboembolic events), kidney issues, and plastic bronchitis are also long-term concerns. Despite these challenges, medical advancements continue to enhance outcomes, but for some, a heart transplant may become necessary if the Fontan circulation can no longer adequately support the body.