In these patients although the left ventricle is able to supply some blood flow to the rest of the body the overall left ventricular systemic output remains inadequate.In all of these cases blood is unable to be pumped to the rest of the body by the left ventricle. The neonate is reliant on blood flowing through an atrial septal defect to mix oxygenated and deoxygenated blood, and on a patent ductus arteriosus to allow blood to reach the aorta and the systemic circulation via the right ventricle. This is what defines HLHS as a "single ventricle" defect.Due to the underdevelopment of the left side of the heart in utero, the increased afterload causes hypertension of the left atrium, pulmonary edema, and therefore lung damage to the fetus before birth. Diagnosis
Hypoplastic left heart syndrome can be diagnosed prenatally or after birth via echocardiography. Typical findings include a small left ventricle and aorta, abnormalities of the mitral and aortic valves, retrograde flow in the transverse arch of the aorta, and left-to-right flow between the atria. It is often recognized during the second trimester of pregnancy, between 18 and 24 weeks gestation. Management
Medical
Without life-prolonging interventions, HLHS is fatal, but with intervention, an infant may survive. A cardiothoracic surgeon may perform a series of operations or a full heart transplant.
While surgical intervention has emerged as the standard of care in the United States, other national health systems, notably in France, approach diagnosis of HLHS in a more conservative manner, with an emphasis on termination of pregnancy or compassionate care after delivery.Before surgery, the ductus must be kept open to allow blood-flow using medication containing prostaglandin. Air with less oxygen than normal is used for infants with hypoplastic left heart syndrome. These low oxygen levels increases the pulmonary vascular resistance (PVR) and thus improve blood flow to the rest of the body due to the greater pressure difference between the lungs and body. Achieving oxygen levels below atmosphere requires the use of inhaled nitrogen. Nitric oxide is a potent pulmonary vasodilator, and thus reduces PVR and improves venous return. Any factor that increases PVR will impede right sided flow. Surgical
Surgical operations to assist with hypoplastic left heart are complex and need to be individualized for each patient. A cardiologist must assess all medical and surgical options on a case-by-case basis.Currently, infants undergo either the staged reconstructive surgery (Norwood or Sano procedure within a few days of birth, Glenn or Hemi-Fontan procedure at 3 to 6 months of age, and the Fontan procedure at 1 1/2 to 5 years of age) or cardiac transplantation. Current expectations are that 70% of those with HLHS may reach adulthood. Many studies show that the higher the volume (number of surgeries performed) at a hospital, the lower the mortality (death) rate.