Chapter 65 The Newborn With a Murmur (Case 28)
Patient Care
Clinical Thinking
• Check vital signs, including four extremity blood pressure readings and oxygen saturation in the right arm and at least one leg. An oxygen saturation that is dramatically different preductus (right arm) and postductus (other limbs) suggests a serious congenital heart defect (CHD). Blood pressure in the legs that is significantly lower than one taken in the arms strongly suggests coarctation of the aorta. Palpation of the femoral pulses is also important— pulses that are difficult or impossible to palpate should raise your suspicion for coarctation.
History
• Elicit family history of CHD, especially in a parent or sibling. The baseline incidence of CHD across all populations is just under 1%. However, with an affected first-degree relative, the risk for CHD increases to 5% to 10% for the infant.
• Have any infants died shortly after birth? Any late miscarriages or children in the family with chromosome anomalies?
Physical Examination
• Check vital signs (weight, height, head circumference, heart rate, respiratory rate, temperature, four extremity blood pressure readings, and oxygen saturation).
• Perform a complete examination. Focus on the cardiovascular system and any findings suggestive of genetic syndromes. Many genetic syndromes have associations with specific congenital heart defects, such as the correlation between Down syndrome and atrioventricular (AV) canal defects, Turner syndrome and coarctation of the aorta, or Noonan syndrome and pulmonic stenosis.
• Inspect and palpate the precordium for chest wall deformities, cardiac thrills, and the point of maximal impulse. Determine where the murmur is heard best, its timing in the cardiac cycle (systole or diastole), any patterns of radiation, its intensity (1 to 6), and any other defining characteristics. Check pulses in both arms and legs. An infant with diminished or absent femoral pulses has coarctation of the aorta until proved otherwise.
Tests for Consideration
Clinical Entities: Medical Knowledge
| Patent Ductus Arteriosus | |
| Pϕ | The ductus arteriosus, essential to fetal circulation, allows blood to bypass the unused lungs and flow directly from the pulmonary artery to the aorta. This muscular artery functionally closes after birth, usually within the first 24 hours, and should be completely closed by 2 to 3 weeks of age. When closure fails to occur, the ductus remains patent, maintaining a connection between the pulmonary artery and the aorta. With a large ductus there is significant shunting of blood from the aorta to the pulmonary artery because of the higher left-sided pressure. The persistent excessive pulmonary blood flow may lead to congestive heart failure (CHF). |
| TP | Every newborn has a PDA at birth. Many times ductus is audible while closing. This murmur is classically described as a “continuous machinery murmur”; however, it may be heard only in systole. A small persistent PDA is asymptomatic. With a large PDA, CHF may develop, and the infant will develop tachypnea, tachycardia, poor feeding, and failure to thrive. |
| Dx | Definitive diagnosis is made with echocardiogram; however, an experienced pediatrician or pediatric cardiologist can often make this diagnosis based on auscultation of the characteristic continuous machinery murmur heard below the left clavicle. |
| Tx | Treatment depends on the size of the ductus and age of the infant. In most term infants, “watchful waiting” is appropriate, because most PDAs will close spontaneously in the first several weeks. In extremely premature infants, PDAs may be surgically ligated or treated medically with indomethacin. PDAs may also be closed in the cardiac catheterization laboratory in older children. See Nelson Essentials 61 and 143. |
| Ventricular Septal Defect | |
|---|---|
| Pϕ | Ventricular septal defects are most commonly located in the membranous septum just below the aortic and pulmonic valves, or in the muscular septum, and result in left-to-right shunting and increased pulmonary blood flow. A small VSD produces turbulent blood flow, and frequently a loud murmur, but is rarely problematic. A large VSD may be asymptomatic with no murmur in the first few weeks of life until pulmonary vascular resistance drops and the pressure gradient from left ventricle to right increases, resulting in increased blood flow through the defect and an audible murmur. Over the first few months of life, the volume overload to the lungs with a large VSD will lead to CHF. VSDs constitute 20% of all CHD. |
| TP | A small VSD is asymptomatic but produces a harsh holosystolic murmur. With a large VSD, there is often development of CHF over the first few months of life with tachypnea, tachycardia, poor feeding, and inadequate weight gain, in addition to the characteristic murmur. |
| Dx | Diagnosis is made based on clinical findings and echocardiogram. |
| Tx | A small VSD will rarely require treatment, and many close over time. A large VSD with uncontrollable heart failure will require surgical repair. Infants are often treated preoperatively with furosemide and digitalis to improve the heart function and facilitate weight gain and nutritional status before definitive repair. Many defects get smaller with time and eventually close, so watchful waiting is often indicated in the absence of CHF. See Nelson Essentials 143. |
| Coarctation of the Aorta | |
| Pϕ | This obstructive lesion is caused by a narrowing in the aorta, most commonly located at the origin of the ductus arteriosus and involving varying segment lengths of the aorta. It is frequently associated with bicuspid aortic valve. There is diminished lower extremity (LE) blood flow, with decreased LE blood pressure and decreased or absent pulses in the legs with strong upper extremity pulses. In its extreme form there is complete interruption of the aorta, which is a life-threatening, ductal-dependent lesion. |
| TP | There is a systolic murmur along the left sternal border with a loud second heart sound. There are decreased or absent lower extremity pulses with strong upper extremity pulses. A neonate with severe coarctation will have lower extremity hypoperfusion and acidosis when the ductus closes. An infant with strong, easily palpable femoral pulses is unlikely to have coarctation of the aorta. |
| Dx | Diagnosis is made with clinical findings and echocardiogram. |
| Tx | Treatment depends on degree of narrowing. Close monitoring of perfusion and blood pressure is key. An acutely ill neonate requires a prostaglandin E1 infusion to reopen the ductus arteriosus until the child has definitive surgical repair. See Nelson Essentials 143. |
| Pulmonary Valve Stenosis | |
| Pϕ | Pulmonary valve stenosis is caused by narrowing of the pulmonary valve orifice or thickening of the valve leaflets. The valve opens incompletely in systole resulting in right ventricular outflow obstruction in proportion to the degree of narrowing. There is increased right ventricular pressure, with eventual development of right ventricular hypertrophy. |
| TP | There are no symptoms with mild to moderate stenosis. On auscultation there is a harsh systolic ejection murmur heard best at the left upper sternal border and possibly an associated click. |
| Dx | Diagnosis is made with echocardiogram, along with a careful evaluation for rarely associated diagnoses such as Noonan syndrome. |
| Tx | A mild degree of pulmonary valve stenosis is generally well tolerated for many years; however, more severe forms may require early intervention. In its most severe form, pulmonary valve stenosis is a life-threatening, ductal-dependent lesion that requires prompt intervention in the first few days of life, often initially with balloon valvuloplasty. See Nelson Essentials 143. |
| Peripheral Pulmonary Stenosis | |
|---|---|
| Pϕ | Peripheral pulmonary stenosis (PPS) is due to the acute angle that the left and right pulmonary arteries form where they branch from the main pulmonary artery. |
| TP | There are no symptoms, and auscultation reveals a characteristic soft systolic murmur heard best at the left upper sternal border with radiation to both axillae. |
| Dx | Diagnosis is most often clinical, but definite diagnosis is with echocardiogram. |
| Tx | No treatment is required in most cases. This innocent murmur resolves as the infant grows. If a murmur thought to be from PPS persists beyond 6 months of age, cardiology referral should be considered. See Nelson Essentials 143. |
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