EVAN S. FIELDSTON
HISTORY OF PRESENT ILLNESS
A 5-week-old Caucasian boy presented to the emergency department with worsening cough and respiratory difficulty. Two weeks prior to admission he was evaluated by his primary physician for poor weight gain and periodic emesis. His weight of 3050 g was the same as his birth weight. He had hemoccult positive stool and was diagnosed as being allergic to cow’s milk protein. His formula was changed to a protein hydrolysate formula. One week prior to admission, his weight had increased to 3100 g. However, he began having more frequent episodes of emesis. Three days prior to admission he developed a cough, tachypnea, and audible wheezing. On being evaluated at a nearby hospital he was diagnosed with bronchiolitis, and treated with albuterol. His tachypnea has not improved despite receiving albuterol every 4 hours. His cough has increased in frequency. He is evaluated in the emergency department for worsening cough and continued tachypnea. His parents mention that the infant has always appeared dusky with crying but this color change has occurred more frequently during the past few days. He has also had numerous episodes of posttussive emesis. During the past three days he has taken only 2 ounces of formula every 4 hours. The parents deny ill contacts, diarrhea, and lethargy. Both parents smoke but only outside the home. There are no pets.
The boy was born at 37 weeks gestation after an uncomplicated pregnancy. The mother’s group B Streptococcus colonization status was not known at the time of delivery so she received two doses of ampicillin prior to delivery. The infant’s Apgar scores were 7 and 8 at 1 and 5 minutes, respectively. He had not previously required hospitalization.
T 37.7°C; HR 160 bpm; RR 60/min; BP 78/37 mmHg; SpO2 88% in room air
Weight 3.0 kg (<5th percentile); Length 49 cm (<5th percentile)
Physical examination revealed a cyanotic infant in moderate respiratory distress. The anterior fontanelle was open and flat. There was no conjunctival injection or pallor. There were no oral mucosal ulcerations. Capillary refill was brisk. The heart sounds were normal. Femoral pulses were palpable and equal. There were intercostal retractions. There were rales and wheezes present diffusely. The liver edge was palpable 3 cm below the right costal margin. The remainder of the examination was normal.
Laboratory analysis revealed 10 200 white blood cells/mm3 with 76% segmented neutrophils, 19% lymphocytes, and 3% monocytes. The hemoglobin was 13.0 g/dL and there were 350 000 platelets/mm3. Hepatic function panel was as follows: total bilirubin, 0.3 mg/dL; alanine aminotransferase, 32 U/L; aspartate aminotransferase, 66 U/L. Prothrombin and partial thromboplastin times and fibrinogen split products were normal. Blood cultures were obtained. Chest radiograph revealed diffuse interstitial pulmonary edema but a normal cardiothymic silhouette.
COURSE OF ILLNESS
The patient was treated with ampicillin and cefotaxime for presumed bacterial sepsis. He also received albuterol. His respiratory status progressively worsened. An arterial blood gas revealed a pH 7.22; PCO265 mmHg; PO2 45 mmHg. The patient required endotracheal intubation. Electrocardiogram suggested a possible diagnosis (Figure 1-7A).
FIGURE 1-7A. Electrocardiogram with right axis deviation (QRS axis = 135°) and right ventricular hypertrophy.
DISCUSSION CASE 1-5
In an infant with cyanosis and respiratory distress, bacterial or viral sepsis must be considered. Children with either viral bronchiolitis or pertussis may present with cyanosis, respiratory symptoms, and rapid deterioration. In this child, the history of periodic cyanosis with crying since birth provided a clue to the diagnosis being a congenital cardiac condition. The differential diagnosis includes a large ventricular septal defect (VSD), patent ductus arteriosus (PDA), truncus arteriosus, atrioventricular canal, single ventricle without pulmonary stenosis, and total anomalous pulmonary venous connection (TAPVC). This condition had been called total anomalous pulmonary venous return (TAPVR), but “connection” is deemed anatomically more appropriate for the range of findings. Unlike TAPVC, the other cardiac anomalies listed typically have electrocardiographic evidence of left atrial or left ventricular hypertrophy. Children with TAPVC have right ventricular hypertrophy.
Electrocardiogram (Figure 1-7A) revealed right axis deviation (QRS axis = 135°) and right ventricular hypertrophy. Echocardiogram revealed a large and dilated right ventricle with a moderately hypoplastic left atrium and a patent foramen ovale. The pulmonary veins merged to form a common vein that drained into the portal venous system below the diaphragm. No pulmonary veins entered the left atrium. There were no other cardiac defects. The echocardiogram findings confirmed the diagnosis of infradiaphragmatic total anomalous pulmonary venous connection (TAPVC) (Figure 1-7B).
FIGURE 1-7B. Echocardiogram for infradiaphragmatic total anomalous pulmonary venous connection (TAPVC) shows large and dilated right ventricle with a moderately hypoplastic left atrium and a patent foramen ovale. The pulmonary veins merged to form a common vein that drained into the portal venous system below the diaphragm. No pulmonary veins entered the left atrium.
INCIDENCE AND ETIOLOGY
TAPVC defines an anomaly in which there is no direct connection between the pulmonary veins and the left atrium. Instead, the pulmonary veins merge to form a common pulmonary vein that connects either to one of the systemic veins or directly to the right atrium. During intrauterine life, the malformation does not compromise fetal circulation because pulmonary arterial resistance is high and some blood flows into the systemic circulation through the patent foramen ovale (PFO). The combined systemic and pulmonary blood flow to the lungs is only mildly elevated. After birth, as pulmonary resistance falls, a progressively larger proportion of the mixed venous blood flows to the lungs, causing massive pulmonary overcirculation.
Several classification schemes have been proposed based on physiologic or prognostic implications of the anomalous connections (Figure 1-7B). Generally, the connections are divided by whether the pulmonary veins merge with the coronary sinus of the right atrium (cardiac, 20% of cases) or with the systemic venous circulation above (supracardiac, 50% of cases) or below (infradiaphragmatic, 20% of cases) the diaphragm. Approximately 10% of cases are mixed.
In TAPVC, because all venous blood ultimately returns to the right atrium, a communication between the right and left sides of the heart is necessary to sustain life. It also explains why there is right ventricular hypertrophy. A patent foramen ovale or an atrial septal defect allows free communication between the two atria and, therefore, is considered part of the disorder. Without this connection, the anomaly would be fatal because of lack of systemic blood flow. Other intracardiac anomalies occur in up to one-third of cases and include common atrioventricular canal, transposition of the great arteries, tetralogy of Fallot, and hypoplastic left heart syndrome. Total anomalous pulmonary venous drainage directly into the right atrium occurs in patients with visceral heterotaxy and polysplenia.
The incidence of TAPVC is not clear. TAPVC occurred in 2% of cases in an autopsy series of 800 children with congenital cardiac disease who died in the first year of life. TAPVC also occurred in 41 (1.5%) of 2659 infants with cardiovascular malformations identified in the Baltimore-Washington Infant Study. There is no sex prevalence in TAPVC except for in infradiagphragmatic TAPVC, which is more prevalent in males than in females (3:1).
FIGURE 1-7C. Total anomalous pulmonary venous connection variants. Total anomalous pulmonary venous connection variants. (A) Supracardiac. Both right (RPV) and left (LPV) pulmonary veins join a common pulmonary venous confluence behind the heart that drains via a vertical vein to the undersurface of the left innominate vein and then to the right atrium. (B) Cardiac. The pulmonary venous confluence connects to the coronary sinus (CS) and then to the right atrium via the coronary sinus ostium. (C) Infradiaphragmatic. The pulmonary venous confluence drains inferiorly via a vertical vein to the portal vein (PV) or hepatic veins (HV) and then to the right atrium. (D) Mixed connections. Left pulmonary veins drain to the left innominate vein (LIV) and right pulmonary veins to the coronary sinus in this example. SV, splenic vein; SMV, superior mesenteric vein. (Part C reproduced, with permission, from Fuster V et al. Hurst’s The Heart. 13th ed. New York: McGraw-Hill, 2011.)
Clinical presentation of children with TAPVC depends on the presence or absence of pulmonary venous obstruction. Most children without obstruction present with tachypnea and failure to thrive with gradually worsening cyanosis and congestive heart failure. Approximately 50% of affected infants show symptoms in the first month of life and the remainder in the first year. Physical examination usually reveals cyanosis due to lack of left-sided flow of oxygenated blood, as well as tachpynea and dyspnea owing to pulmonary edema. Cyanosis may be minimal initially but increases as congestive heart failure progresses. Cyanosis occurs because the pulmonary veins carry oxygenated blood to the systemic venous circulation instead of to the left atrium. Congestive heart failure occurs because of increased pulmonary blood flow and pulmonary hypertension. Hepatomegaly and peripheral edema often accompany cardiac failure. There is typically no cardiac murmur, although there may be a systolic ejection murmur at the left upper sternal border. Cardiac examination may reveal right ventricular heave, fixed split S2, and an S3 gallop.
Obstruction is more common in children with infradiaphragmatic TAPVC because of venous compression as the common venous trunk passes through either the esophageal hiatus of the diaphragm or the portal venous circulation. Most children with infradiaphragmatic TAPVC and one-third of children with supracardiac TAPVC present with pulmonary venous obstruction. These infants are usually asymptomatic at birth but develop symptoms within the first few weeks of life. Infants with pulmonary venous obstruction present with rapidly progressive dyspnea, pulmonary edema, cyanosis, and congestive heart failure.
Alteration in the character of the cry (“neonatal dysphonia”) occurs in one-fourth of infants with supracardiac TAPVC because of compression of the left recurrent laryngeal nerve as it passes the dilated common pulmonary vein. Infants with infradiaphragmatic TAPVC may have worsening cyanosis with swallowing, straining, and crying as a consequence of interference of pulmonary venous outflow by increased intraabdominal pressure or impingement of the esophagus on the common pulmonary vein as it exits through the esophageal hiatus. The child in the presented case did not have pulmonary venous obstruction despite having infradiaphragmatic TAPVC. His history of cyanosis with crying is consistent with infradiaphragmatic TAPVC.
The diagnosis should be suspected on the basis of clinical presentation and workup should include the following studies.
Electrocardiogram. A tall peaked P wave in lead II or in the right precordial leads characterizes right atrial enlargement, a feature of TAPVC without obstruction. Right atrial enlargement is not usually present in TAPVC with obstruction because of fulminant presentation very early in life. Right ventricular hypertrophy is manifested by high voltages in the right precordial leads. Right axis deviation is always present because of right-sided hypertrophy (Figure 1-7A).
Chest radiograph. Lung fields reflect increased pulmonary blood flow. The cardiothymic silhouette may be normal, but may reveal cardiomegaly or “figure of 8” or “snowman” sign in supracardiac TAPVC, typically after 4 months of age.
Echocardiogram. Echocardiogram reveals signs of right ventricular volume overload. The right atrium is enlarged. The right ventricle is hypertrophied and dilated, compressing the intraventricular septum. The pulmonary arteries are dilated. The pulmonary veins are seen forming a common vein behind the heart. The size and orientation of the venous confluence are important for surgical planning. Associated intracardiac defects may be identified.
Cardiac catheterization. The accuracy of Doppler echocardiography precludes the routine need for diagnostic catheterization. Right ventricular pressures are usually equal to systemic pressures.
While awaiting surgery, prostaglandin E1 (PGE1) should be administered to maintain patency of the ductus arteriosus. Complete surgical repair should be performed as early as possible. If there is obstruction, the repair should be done emergently. A large side-to-side anastomosis is created between the left atrium and the common pulmonary vein. The distal portion of the common pulmonary vein is occasionally ligated. The foramen ovale or atrial septal defect is also closed. A hypoplastic left atrium may require surgical enlargement.
Postoperative pulmonary venous obstruction complicates the course in approximately 17% of infants. This complication typically occurs within 6 months of the original repair and is associated with poor outcomes. Risk factors for death include earlier presentation after TAPVC repair, diffusely small pulmonary veins at presentation of postoperative pulmonary venous obstruction, and an increased number of lung segments affected by obstruction. Residual stenosis at the left atrialvenous anastomosis created at operative repair develops in 10% of children. This stenosis requires reintervention and patch plasty. Late atrial arrhythmias develop in a small number of patients.
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