Published on 21/03/2015 by admin
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Chapter 21 HEART MURMUR
Theodore X. O’Connell
As many as 90% of children will have an audible heart murmur at some time, yet the incidence of structural congenital heart disease is estimated to be less than 1% of all live births. A murmur may be heard in 60% of healthy newborn babies. As such, the physician must determine which patients require further evaluation.
Features of concern in infants include feeding intolerance, failure to thrive, respiratory symptoms, or cyanosis. In older children, chest pain (especially with exercise), syncope, exercise intolerance, or a family history of sudden death in young people should raise the physician’s level of suspicion. Other features that increase the likelihood of cardiac pathology include malformation syndromes, increased precordial activity, decreased femoral pulses, abnormal second heart sounds, clicks, a loud or harsh murmur, and increased intensity of the murmur when the patient stands.
The clinical diagnosis of a normal or innocent murmur should occur in the setting of an otherwise normal history, physical examination, and appearance. The innocent systolic murmurs are soft (grade 1 or 2) and ejection in quality. Normal murmurs are never solely diastolic. The intensity of an innocent murmur is grade 3 or less and, consequently, is never associated with a palpable thrill. Most murmurs, both innocent and organic, may be accentuated by fever, anemia, or increased cardiac output.
The pathologic systolic murmur occurs early in systole and can be quite loud. Diastolic murmurs are much less common in children, and the presence of a diastolic murmur indicates that structural heart disease is present and warrants referral. Continuous precordial murmurs in infants are also generally pathologic, with the exception of the venous hum. The venous hum should resolve in the supine position or with gentle compression of the jugular vein. Patients with venous hums do not require pediatric cardiology referral.
Holosystolic murmurs occur when a regurgitant atrioventricular valve is present or in association with most ventricular septal defects. Ejection murmurs may arise from narrowing of the semilunar valves or outflow tracts. Innocent murmurs are almost exclusively systolic ejection in nature. They are generally soft, never associated with a palpable thrill, and vary considerably with positional changes. Early systolic murmurs are associated exclusively with small muscular ventricular septal defects. Mid-to-late systolic murmurs are often heard in association with mitral valve prolapse.
Diastolic murmurs may be associated with regurgitation of the aortic or pulmonary valves, stenosis of an atrioventricular valve, or increased flow across an atrioventricular valve. Early diastolic murmurs arise from either aortic or pulmonary valve insufficiency. Mid-diastolic murmurs occur because of either increased flow across a normal tricuspid valve or mitral valve or normal flow across an obstructed or stenotic tricuspid or mitral valve. Late diastolic or crescendo murmurs are caused by stenotic or narrowed atrioventricular valves.
Most innocent heart murmurs in healthy term infants are related to peripheral pulmonary stenosis, which is reduced in two thirds of cases by 6 weeks of age and in most others by 6 months. The murmur is soft (grade 1 or 2), ejection in quality, and best heard anteriorly at the left upper sternal border with characteristic transmission to the axillae and back bilaterally. No associated signs or symptoms of heart disease are present. The murmur of atrial septal defect may mimic this murmur but is generally heard in later infancy or childhood. Pathologic peripheral pulmonary stenosis is typically more severe, has a louder murmur, and does not regress over time. If peripheral pulmonary stenosis is suspected in the term infant, close follow-up is indicated. If the murmur intensifies or persists after 6 months of age, cardiology referral is indicated.
Isolated ventricular septal defects are the most common congenital heart defect identified through the first three decades of life. Infants with ventricular septal defect can present in different ways, and presentation is determined by the size of the defect and the status of the pulmonary vascular resistance. Most commonly the murmur is detected at 2 to 6 weeks of age. The infant with a small ventricular septal defect may have a loud murmur but appears healthy with normal growth and no cardiac symptoms. The precordial activity is normal, and there typically is no palpable systolic thrill. The infant with a moderate-sized ventricular septal defect often has poor weight gain and may have dsypnea and diaphoresis, particularly with feedings. The murmur is loud, is frequently associated with a systolic thrill, is harsh and holosystolic, and obscures the first and second heart sounds. A prominent third heart sound or diastolic flow murmur can be heard at the cardiac apex. The infant with a large ventricular septal defect has significant clinical symptoms such as feeding problems, failure to thrive, and irritability. The murmur is soft, short, and early systolic. There is a marked right ventricular heave with a loud and single second heart sound. A prominent third heart sound and diastolic rumble are common, and hepatomegaly is usually present. Cardiology referral is indicated for children with suspected ventricular septal defect.
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