8.2 Congenital Heart Disease & Cardiac Conditions

Why Infants with Congenital Heart Disease Fail to Thrive

Congenital heart disease (CHD) produces growth failure through three overlapping mechanisms. First, increased energy expenditure: heart failure and tachypnea raise resting metabolic rate, and the work of feeding itself becomes costly. Second, decreased intake: infants fatigue mid-feed, become tachypneic at the breast or bottle, and stop before meeting needs. Third, malabsorption and gut dysfunction: reduced splanchnic perfusion, elevated central venous pressure, and (in Fontan physiology) protein-losing enteropathy impair nutrient absorption. Lesions with pulmonary overcirculation (large ventricular septal defects, single-ventricle physiology) are the highest-risk feeding phenotypes.

Calorie Concentration and Feeding Management

Standard breast milk and formula provide 20 kcal/oz (0.67 kcal/mL); infants with CHD typically need 24-30 kcal/oz. Breast milk is fortified with powdered formula or human milk fortifier; formula is concentrated by adjusting the powder-to-water ratio. Concentration requires careful recipe math: each step raises osmolality and renal solute load, so increases are made gradually (e.g., 22, 24, 26 kcal/oz) while monitoring tolerance — emesis, stool pattern, abdominal distension — and hydration status.

Feeding technique matters as much as the recipe. Offer smaller, more frequent feeds, choose nipple flows that limit work, and cap each oral attempt at about 20-30 minutes — beyond that, the infant expends more energy feeding than the feed provides. When oral intake cannot sustain growth velocity, nasogastric (NG) supplementation (bolus or overnight continuous) is standard; nasojejunal (NJ) feeds are reserved for significant reflux or aspiration risk. Prolonged tube feeding warrants early occupational/speech therapy to prevent oral aversion.

Fluid, Sodium, and Diuretics

Fluid restriction in heart failure creates a dilemma in infants: limiting volume limits nutrition, so the answer is usually to concentrate the feed rather than restrict calories. Loop diuretics such as furosemide waste potassium and can cause hypokalemia, hyponatremia, hypochloremic metabolic alkalosis, and (chronically) hypercalciuria with nephrocalcinosis; potassium supplementation or a potassium-sparing agent is often needed. Thiazides add further sodium and potassium losses. Monitor electrolytes regularly and remember that hyponatremia in CHD is usually dilutional — managed with fluid strategy, not salt loading.

Perioperative Nutrition

Preoperatively, minimize NPO (nil per os) time according to anesthesia fasting guidelines to protect nutritional status. Necrotizing enterocolitis (NEC) risk is elevated in single-ventricle physiology (e.g., hypoplastic left heart syndrome) because of compromised mesenteric perfusion; feeds are advanced cautiously, and human milk is preferred for its protective effect.

Chylothorax — leakage of chyle into the pleural space — complicates a meaningful share of cardiothoracic surgeries, especially those near the thoracic duct. Management is dietary: a medium-chain triglyceride (MCT)-enriched, low long-chain-fat diet (MCTs are absorbed directly into the portal vein, bypassing intestinal lymphatics) using an MCT-predominant formula, or skimmed/defatted human milk fortified appropriately for infants, continued for approximately 6 weeks while the lymphatic injury heals, then re-challenged with a normal-fat diet. Fat-soluble vitamins and essential fatty acids are monitored during prolonged low-fat therapy.

Fontan Physiology and Cardiac Cachexia

After the Fontan operation, systemic venous pressure is chronically elevated, predisposing to protein-losing enteropathy (hypoalbuminemia, edema, lymphopenia) and plastic bronchitis. Cardiac cachexia — the wasting syndrome of end-stage heart failure — combines anorexia, inflammation, and high metabolic demand and responds poorly to calories alone.

Kawasaki Disease

Kawasaki disease is an acute vasculitis of childhood treated with intravenous immunoglobulin (IVIG) 2 g/kg plus aspirin (anti-inflammatory dosing acutely, then low-dose antiplatelet therapy). Nutrition is supportive; monitor for the disease's anorexia and for coronary artery aneurysms that dictate long-term cardiac follow-up.

Transplant Immunosuppression and Nutrition

After heart transplant, nutrition management shifts to immunosuppressant effects. Corticosteroids increase appetite and weight, cause hyperglycemia, reduce bone mineral density, and suppress linear growth. Calcineurin inhibitors — tacrolimus and cyclosporine — are metabolized by CYP3A4, so grapefruit and grapefruit juice are contraindicated; they also cause hyperkalemia and hypomagnesemia. Food safety is essential in the immunocompromised child: avoid unpasteurized dairy and juices, raw or undercooked meats and eggs, and high-risk deli items, and follow safe food-handling practices. Mycophenolate mofetil commonly causes gastrointestinal side effects — nausea, vomiting, and diarrhea — that can masquerade as feeding intolerance or rejection workups.

Interstage Monitoring and Nutrition Assessment

For infants with single-ventricle physiology discharged between staged palliations (the interstage period, classically after the Norwood procedure and before the bidirectional Glenn), structured home monitoring programs track daily weight and oxygen saturation, because poor weight gain and growth failure predict interstage mortality. A typical weight-gain target is roughly 20-30 g/day in early infancy; falling off that trajectory triggers feed concentration increases or NG supplementation. Routine nutrition assessment in CHD includes weight, length/height, and head circumference plotted on appropriate growth charts, weight-for-length or BMI z-score trends rather than single points, a detailed feeding history (volumes, recipe, duration, fatigue behaviors), and review of diuretic-related electrolytes. Pre-transplant, severe malnutrition worsens surgical outcomes, so nutrition optimization is part of transplant listing readiness; post-transplant, catch-up growth is expected but is blunted while steroid doses remain high.