Evaluation of the Infant or Child with Congenital Heart Disease

Chapter 419 Evaluation of the Infant or Child with Congenital Heart Disease



Daniel Bernstein



The initial evaluation for suspected congenital heart disease involves a systematic approach with three major components. First, congenital cardiac defects can be divided into 2 major groups based on the presence or absence of cyanosis, which can be determined by physical examination aided by pulse oximetry. Second, these 2 groups can be further subdivided according to whether the chest radiograph shows evidence of increased, normal, or decreased pulmonary vascular markings. Finally, the electrocardiogram can be used to determine whether right, left, or biventricular hypertrophy exists. The character of the heart sounds and the presence and character of any murmurs further narrow the differential diagnosis. The final diagnosis is then confirmed by echocardiography, CT or MRI, or cardiac catheterization.



Acyanotic Congenital Heart Lesions


Acyanotic congenital heart lesions can be classified according to the predominant physiologic load that they place on the heart. Although many congenital heart lesions induce more than one physiologic disturbance, it is helpful to focus on the primary load abnormality for purposes of classification. The most common lesions are those that produce a volume load, and the most common of these are left-to-right shunt lesions. Atrioventricular (AV) valve regurgitation and some of the cardiomyopathies are other causes of increased volume load. The second major class of lesions causes an increase in pressure load, most commonly secondary to ventricular outflow obstruction (pulmonic or aortic valve stenosis) or narrowing of one of the great vessels (coarctation of the aorta). The chest radiograph and electrocardiogram are useful tools for differentiating between these major classes of volume and pressure overload lesions.



Lesions Resulting in Increased Volume Load


The most common lesions in this group are those that cause left-to-right shunting (see Chapter 420): atrial septal defect, ventricular septal defect (VSD), AV septal defects (AV canal), and patent ductus arteriosus. The pathophysiologic common denominator in this group is communication between the systemic and pulmonary sides of the circulation, which results in shunting of fully oxygenated blood back into the lungs. This shunt can be quantitated by calculating the ratio of pulmonary to systemic blood flow, or Qp : Qs. Thus, a 2 : 1 shunt implies twice the normal pulmonary blood flow.


The direction and magnitude of the shunt across such a communication depend on the size of the defect, the relative pulmonary and systemic pressure and vascular resistances, and the compliances of the 2 chambers connected by the defect. These factors are dynamic and may change dramatically with age: Intracardiac defects may grow smaller with time; pulmonary vascular resistance, which is high in the immediate newborn period, decreases to normal adult levels by several weeks of life; and chronic exposure of the pulmonary circulation to high pressure and blood flow results in a gradual increase in pulmonary vascular resistance (Eisenmenger physiology, Chapter 427.2). Thus, a lesion such as a large VSD may be associated with little shunting and few symptoms during the initial weeks of life. When pulmonary vascular resistance declines in the next several weeks, the volume of the left-to-right shunt increases, and symptoms begin to appear.


The increased volume of blood in the lungs decreases pulmonary compliance and increases the work of breathing. Fluid leaks into the interstitial space and alveoli and causes pulmonary edema. The infant acquires the symptoms we refer to as heart failure, such as tachypnea, chest retractions, nasal flaring, and wheezing. The term heart failure

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Jun 18, 2016 | Posted by in PEDIATRICS | Comments Off on Evaluation of the Infant or Child with Congenital Heart Disease

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