Pediatric Subvalvar Aortic Stenosis Clinical Presentation

Symptoms of SAS are rare in infancy and uncommon in early childhood, even if the stenosis is severe.

Isolated SAS may be diagnosed relatively late in life because of the progressive nature of the lesion and because patients lack symptoms that prompt evaluation. The diagnosis is frequently made during an evaluation for an asymptomatic heart murmur.

When present, symptoms include dyspnea on exertion, effort syncope and presyncope, angina, orthopnea, heart failure, and sudden cardiac death. Most of these symptoms occur in children, adolescents, and young adults aged 10-21 years with moderate or severe left ventricular outflow tract (LVOT) obstruction and peak-to-peak pressure gradients of more than 50 mm Hg.

Exertional dyspnea is the most common symptom, occurring in as many as 40% of symptomatic patients. Exertional dyspnea with orthopnea reflects various degrees of pulmonary venous hypertension due to elevated LV filling pressure resulting from impaired diastolic compliance of the hypertrophied LV.

Effort syncope and presyncope occur more frequently in SAS than they do in stenosis of the aortic valve. Syncope during exertion occurs because cerebral perfusion decreases when arterial pressure declines consequent to systemic vasodilation in the presence of a fixed cardiac output. Presyncope may manifest as a graying-out spell or as dizziness on effort because of exertional hypotension.

In pediatric patients, syncope and presyncope at rest are rare. Their presence may indicate a cardiac arrhythmia, notably transient ventricular arrhythmia.

Angina may occur in as many as 25% of symptomatic patients with an LVOT obstruction that is more than mild. Exertion commonly precipitates the condition, and rest relieves it. Angina occurs in the absence of coronary artery disease. It results from the combination of increased oxygen demand by hypertrophied myocardium and reduced oxygen delivery secondary to excessive compression of coronary vessels.

Symptoms of associated congenital heart defects frequently mask those of SAS. In most patients, in fact, SAS is detected in the course of follow-up care for associated congenital heart defects or during evaluation of a heart murmur.

The physical growth of the child with SAS is usually normal. Peripheral pulses are symmetrical and rarely of small volume, unless severe LVOT obstruction is present.

A prominent a wave in the jugular venous pulse occasionally occurs in children with SAS. This wave reflects reduced right ventricular compliance consequent to a hypertrophied ventricular septum.

A palpable carotid thrill and a left parasternal thrill are present in one third of patients with mild SAS (pressure gradient < 50 mm Hg) and in approximately one half of patients with more-than-mild SAS. A forceful LV apical impulse is present in most patients with moderate or severe SAS.

The first heart sound is normal. The second heart sound can be narrowly split or single because of prolonged LV systole. Paradoxical splitting of the second heart sound, which suggests associated LV dysfunction, may occur in severe SAS.

A low-pitched ejection systolic murmur of 2-4/6 intensity is best appreciated in second and third left parasternal spaces, with radiation to suprasternal notch. This murmur is typically present in all cases of isolated SAS. The length of the murmur is proportional to the degree of obstruction.

An ejection click opening the ejection murmur is absent in isolated SAS. This is an important clue for differentiating this murmur from that of aortic valve stenosis.

A high-pitched, early diastolic murmur of aortic regurgitation in the same area is present in 30-50% of patients. A pansystolic murmur of mitral regurgitation due to dysfunction of the papillary muscle is sometimes heard.