Congestive Heart Failure

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Chapter 16 Congestive Heart Failure

PATHOPHYSIOLOGY

Congestive heart failure (CHF) occurs when the heart cannot pump the blood returning to the right side of the heart, provide adequate circulation to meet the needs of organs and tissues in the body, or a combination of the two. The component factors in CHF include preload and circulating volume, afterload, and contractility. Causes include congenital and acquired heart diseases with pressure and/or volume overload, and myocardial insufficiency.

1. Congenital heart disease with pressure or volume overload is a common cause of CHF in pediatric patients. The timing of onset varies fairly predictably with the type of defect (Table 16-1). It is important to note the following:

a. Children with tetralogy of Fallot (TOF) do not develop CHF unless they have undergone a large aorta-to-pulmonary artery shunt procedure such as a Waterston or Potts operation. These procedures are no longer performed.
b. Atrial septal defects (ASD) rarely cause CHF in children.
c. Large left-to-right shunts such as ventricular septal defect and patent ductus arteriosus (PDA) do not cause CHF before 6 to 8 weeks of age in full-term infants, because pulmonary vascular resistance (PVR) does not fall low enough to allow the left-to-right shunt until this time. However, CHF may occur earlier in premature infants with these lesions as a result of an earlier fall in PVR.

2. Acquired heart disease of various etiologies can result in CHF. The age of onset of CHF is less predictable with acquired heart disease than with congenital heart disease; however, there are some general considerations:

a. Metabolic abnormalities in newborns including severe hypoxia and acidosis, hypoglycemia, and hypocalcemia
b. Endocardial fibroelastosis, a rare primary myocardial disease, causes CHF in infants. In 90% of the cases, signs of CHF are evident in the first 8 months of life.
c. Viral myocarditis can occur in small children, usually over 1 year of age; it may occur in newborns with sudden onset and severe illness.
d. Acute rheumatic carditis is an occasional cause of CHF primarily in school-aged children.
e. Rheumatic valvular diseases with volume overload lesion such as mitral regurgitation (MR) or aortic regurgitation (AR) cause CHF in older children. Uncommon in industrialized countries.
f. Idiopathic dilated cardiomyopathy may cause CHF at any age during childhood and adolescence.
g. Cardiomyopathies associated with muscular dystrophy and Friedreich’s ataxia may cause CHF in older children and adolescents.
h. Doxorubicin-associated cardiomyopathy may occur months to years after completion of chemotherapy in children with malignancies.

3. Other causes:

a. Complete heart block associated with structural heart defects in the newborn period and early infancy.
b. Supraventricular tachycardia (SVT) in early infancy.
c. Severe anemia at any age.
d. Hydrops fetalis in the newborn.
e. Sicklemia beyond the newborn period.
f. Acute hypertension following acute infectious glomerulonephritis in school-aged children. Hypertension is related to fluid retention with poor renal function.
g. Bronchopulmonary dysplasia in premature infants causes predominantly right-sided heart failure in the first few months of life.
h. Acute cor pulmonale due to airway obstruction as seen with large tonsils can cause CHF at any age, but is most common during early childhood.

Table 16-1 Causes of Congestive Heart Failure Due to Congenital Heart Disease According to the Time of Occurrence

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Age or Time of Occurrence Cause
At birth a. HLHS
b. Volume overload lesions (e.g., severe TR or PR, large systemic AV fistula)
First week a. TGA
b. PDA in small premature infants
c. HLHS (with more favorable anatomy)
d. TAPVR, particularly those with pulmonary venous obstruction
1–4 weeks a. COA (with associated anomalies)
b. Critical AS

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