Week 24: Peds Cardio and Bonus Back Pain

The classic cyanotic congenital heart diseases can be remembered by the “5 Ts”: truncus arteriosus, transposition of the great vessels, tricuspid atresia, tetralogy of Fallot, and total anomalous pulmonary venous return. Other cyanotic cardiac lesions include Ebstein’s anomaly, pulmonary atresia, severe pulmonary stenosis, hypoplastic left heart syndrome, and hypoplastic right heart syndrome.

Atrial septal defect (A), patent ductus arteriosus (B), and ventricular septal defect (D) are lesions with left-to-right shunts and are associated with an increase in pulmonary blood flow. These acyanotic lesions usually manifest with congestive heart failure, rather than cyanosis, within the first 6 months of life.

Systemic perfusion depends on a patent ductus arteriosus (PDA). The closure of the ductus results in rapid, progressive cardiogenic shock and circulatory collapse. Therefore, administration of prostaglandin E1 (PGE1) will maintain a patent ductus arteriosus and should be given. Because 100% oxygen accelerates ductal closure in HLHS, it is acceptable to decrease the FiO₂ to 21% to increase pulmonary vascular resistance and promote systemic blood flow across the PDA. Controlled hypoventilation and positive end-expiratory pressure may also be utilized to augment systemic perfusion by increasing pulmonary vascular resistance. There is no role for diuretics, such as furosemide.

This newborn has a positive hyperoxia test, indicating probable cyanotic congenital heart disease. Transposition of the great arteries is the only cyanotic congenital heart disease listed. Other common causes of cyanotic congenital heart disease include tetralogy of Fallot, tricuspid atresia, total anomalous pulmonary venous return, and pulmonary atresia or stenosis.

A fever is a common concern of parents prompting many to present for medical care. Fevers are an important clinical symptom caused by a change in the thermoregulatory hypothalamic set point for body temperature. It is frequently a symptom of infection but can also be caused by drugs, immunization reactions, CNS dysfunction, malignancy, and chronic inflammatory conditions. Management is to find and treat the cause of the fever. There is no evidence that reducing a fever decreases the morbidity or mortality of an illness, with the possible exception of patients who are critically ill or cannot tolerate the metabolic demands of a fever. This includes patients with an already elevated metabolic state (shock, burns, and post-operative patients), patients with major head trauma, post-cardiac arrest, or those with underlying neurologic or cardiopulmonary disease such as cardiomyopathy (A).

Coarctation of the aorta usually presents as congestive heart failure and cardiogenic shock in the neonatal period due to increased afterload caused by narrowing of the aorta. In mild cases, patients can develop arterial collateral vesselsthat partially bypass the aortic obstruction. These patients usually remain asymptomatic. The diagnosis is often made when incidental hypertension is noted during the evaluation of other problems such as trauma or routine illness. In older children, adolescents, and adults, coarctation of the aorta is best diagnosed clinically by simultaneous palpation of femoral and brachial pulses. Blood pressure in both arms and one leg must be determined; a pressure difference of more than 20 mm Hg in favor of the arms may be considered evidence of coarctation of the aorta. The chest radiograph in these patients may demonstrate rib notching secondary to collateral vessels.

Referring the patient for follow-up (A) is always a good idea but, in this case, would delay her diagnosis of coarctation of the aorta. Many patients exhibit “white coat hypertension,” and a repeat blood pressure is usually normal. However, hypertension in the pediatric age group may have a secondary cause and mandates a thorough evaluation. Renal artery stenosis due to fibromuscular dysplasia (C) is a secondary cause of hypertension seen most commonly in young female patients. Renal ultrasound may show stenosis of the renal artery. However, patients with this condition will have no pulse or blood pressure discrepancies. Patients with hypertension should be started on antihypertensive medications (D) to reduce the future risk of cardiovascular disease. While this patient may require such therapy in the future, her underlying pathology (i.e., coarctation of the aorta) should first be addressed.

A useful bedside test to determine the etiology of a child’s cyanosis (respiratory versus cardiac) is the hyperoxia test. This test is conducted through use of arterial blood gases and 100% oxygen. With application of 100% oxygen an increase in pO₂ of 220 mm Hg suggests lung disease, a pO₂ of 100 to 220 mm Hg requires an evaluation for congenital heart disease, a pO₂100 mm Hg suggests cyanotic congenital heart disease, and a pO₂ 40 to 50 mm Hg would be likely due to transposition of the great arteries (TGA) with poor mixing. If an ABG is not available, the test can also be performed by measuring the oxygen saturation before and after application of 100% oxygen. The oxygen saturation should increase by at least 10% in the presence of a pulmonary process. Therefore, this patient probably has lung disease, such as bronchiolitis. Of note, bronchiolitis may not be associated with cough, rhinorrhea, or wheezing in infants less than 1 month of age.

Based on the hyperoxia test this newborn has cyanotic congenital heart disease, ruling out critical aortic stenosis and coarctation of the aorta. Based on the chest radiograph and ECG, she most likely has tetralogy of Fallot. Boot shaped heart is a buzz word on the boards for ToF and represents RV hypertrophy. This is also hinted at on the ECG. In concert this likely indicates a TofF. TofF is also more common than other cyanotic congenital lesions (represents 10% of congenital heart defects, while transposition of the great arteries is only 5%).

Recall that transposition of the great vessels produced the “egg on a string” type heart on CXR

The radiograph demonstrates rib notching which is characteristic of coarctation of the aorta. Rib notching occurs secondary to development of collateral arteries that form to bypass the coarctation. Rib notching most often involves ribs four to eight but never involves ribs one or two. Most cases of coarctation are diagnosed in the neonatal period. Adolescents and adults usually present with hypertension. Most persons over 20 years with coarctation will display rib notching. Another radiographic finding is the “figure 3 sign” which represents pre-stenotic dilation of the aortic notch and left subclavian.

TAPVR (B) is diagnosed in the neonatal period. These patients classically exhibit a figure 8 or snowman shaped heart on chest radiograph. Transposition of the great arteries (C) is also diagnosed in the neonatal period and is associated with the classic “egg-on-a-string” chest radiograph that describes the narrow mediastinum from superimposed vessels. An isolated ventricular septal defect (D) is not associated with a characteristic chest radiograph. Minor defects typically go undiagnosed, but larger defects can lead to heart failure if not corrected.

Ventricular septal defect (VSD) is most common, responsible for 25% of all congenital heart defects. Most are small and close spontaneously over time. However, larger lesions may persist, eventually leading to pulmonary hypertension and right-sided heart failure. The classic VSD murmur is holosystolic and best heard at the left lower sternal border.

Atrial septal defects (ASD) (A) are rarely recognized in the neonatal period and typically manifest during adolescence, with dyspnea on exertion or, during adulthood with atrial dysrhythmias. An ASD is associated with a fixed split S2 and a loud S1. Coarctation of the aorta (B) involves a narrowing around the ductus arteriosus. Mild cases usually present later in life with hypertension and a chest radiograph that shows rib notching. The ductus arteriosus (C) usually closes by one week of life. Rarely, it will remain open beyond this, but when it does, a continuous machine-like murmur can be heard at the left upper sternal border.

The most common dysrhythmia in children is paroxysmal supraventricular tachycardia (PSVT). It is differentiated from sinus tachycardia by its abrupt onset, rates >230, the absence of normal P waves, or by little rate variation during stressful activities. Symptoms of PSVT in infants include poor feeding, tachypnea, and irritability. Application of ice to the face has been shown to be an effective method of converting a hemodynamically stable child in SVT to NSR. It is important that when performing this maneuver that you do not occlude the nose or mouth, and apply the ice only over the patient’s forehead, eyes, and bridge of the nose for 10–15 seconds. Adenosine, an AV-nodal blocking agent, can also be administered in stable patients.

It will also cause the patient to cry which will increase intra-abdominal and thoracic pressure, temporarily decreasing venous return, and upon release (for a breath, etc.), there will be venous return that will distend the RA and lead to a greater vagal response. This is an added bonus in infants, as ice to the face alone causes a strong vagal response (ask Dr. Berk).

Applying external ocular pressure (A) is contraindicated in children because it can lead to globe rupture. Having a patient blow on an occluded straw may be an acceptable vagal maneuver, but blowing on the patient’s face with a straw (C) has no benefit. Carotid massage (D) is not recommended in infants or children.