A 4 year old male presents in the office for a preschool physical examination. In the course of the interview, his mother mentions that he seems to get short of breath with exercise recently. It is especially noticeable during his swimming lessons when he tires before the other children do in his class. He has otherwise been in good health since his last physical exam in the previous year. His records for the past year show 3 office visits for minor upper respiratory illnesses, and no emergency room visits. He has never had wheezing during his colds.
Exam: T37.5, P92, R25, BP right arm 97/70, oxygen saturation 98% in room air. Height and weight are at the 25th percentile. He is cooperative and well nourished in no distress. HEENT and neck exams are normal. His chest is symmetrical. Heart: No palpable thrill, normal 1st and 2nd heart sounds; no clicks or rubs; grade 1/6 ejection systolic murmur heard along the left sternal border with radiation to the back between the scapulae; no diastolic murmur. Lungs are clear to auscultation. Abdomen without no organomegaly or masses palpable. Genitalia: normal male. Extremities: Femoral pulses are slightly diminished to palpation; no peripheral edema, clubbing or cyanosis of the nail beds. His neurological is normal.
He receives his immunizations, and tuberculin skin test, and because of the new onset heart murmur, a chest x-ray and EKG are ordered. He returns in 3 days to have his skin test read and to review his cardiac tests. Before entering the exam room the nurse remeasures his vital signs and records in his chart: BP left arm 127/86, P88, R24. His chest x-ray shows a cardiac/thoracic ratio of 0.55, normal cardiac configuration, and normal pulmonary vasculature. His EKG has tall R waves of 40 mm in lead V5, and 35 mm in lead V6. An echocardiogram is performed the following day and demonstrates a coarctation of the aorta, and bicuspid aortic valve. A MRI shows a discrete narrowing of the distal aortic arch just beyond the origin of the left subclavian artery and also reveals an aberrant right subclavian artery originating from the proximal descending aorta below the coarctation.
Coarctation of the aorta is classified as an acyanotic congenital heart defect and belongs to that group of cardiac anomalies that is the result of abnormal fetal cardiac formation, that does NOT cause shunting of blood from the venous to the systemic side of the heart (i.e., it does NOT cause right to left shunting), and that may be manifested and clinically detectable some time after birth. With the advent of fetal echocardiography, these lesions are sometimes detected before birth.
A list of the acyanotic lesions can be made by enumerating the structures encountered by the flow of blood through the different parts of the heart beginning with the venous side. The most common anomalies would thus include: tricuspid valve stenosis/regurgitation, Ebstein's anomaly of the tricuspid valve (can be cyanotic in infants), pulmonic valve stenosis/regurgitation, subvalvular and supravalvular pulmonic stenosis, partial anomalous pulmonary venous drainage to the right side of the heart, atrial septal defect (secundum, primum, sinus venosus), mitral valve stenosis/regurgitation, ventricular septal defect, aortic valve stenosis/regurgitation, subvalvular and supravalvular aortic stenosis, patent ductus arteriosus, and coarctation of the aorta.
Acyanotic congenital lesions account for 70% of all congenital heart disease, the most common of which, as isolated lesions, are ventricular septal defects (most common), patent ductus arteriosus, atrial septal defect and pulmonic stenosis. Coarctation of the aorta accounts for (6%) of all congenital heart disease (1). Patients with Turner's syndrome have coarctation more commonly than the general population.
Coarctation of the aorta results from constriction of the tissue of the distal aortic arch at the junction with the descending aorta and near the insertion of the ductus arteriosus. Various theories have been proposed to explain this maldevelopment. One popular theory associates the presence of ductal tissue encircling the aorta at the site of the coarctation suggesting a constrictive effect of the ductile tissue (2).
Although present at birth, coarctation of the aorta may not cause symptoms until early childhood and sometimes not until late childhood, depending on the severity of the coarctation, and the presence of associated cardiac lesions. If a ventricular septal defect is also present and is large, the coarctation of the aorta will cause increased left to right shunting across the defect, producing congestive heart failure within the first few months of life as the pulmonary resistance decreases after birth. A patent ductus arteriosus located proximal to the coarctation would likewise increase pulmonary shunting through the ductus resulting in congestive heart failure. If the ductus is located distal to the coarctation, signs and symptoms may be delayed.
Other anomalies associated with aortic coarctation include a bicuspid aortic valve (85%) (3) that may obstruct left ventricular output, and an aberrant origin of the right subclavian artery distal to the coarctation (1%) (4). The latter will cause the blood pressure of the right arm to be equal to the leg, and may mislead one from the correct diagnosis. It is important to measure the blood pressure in both arms and at least one leg in order to detect the blood pressure differential caused by an aortic coarctation.
If coarctation of the aorta is an isolated lesion, the typical symptoms may include: shortness of breath with exertion, leg pain with exercise, and rarely, chest pain with exercise. Physical findings include: upper extremity hypertension with a blood pressure differential between arm and leg (obtain BP in both arms and one leg), a systolic murmur heard along the left sternal border and especially well over the back between the scapulae, and diminished and delayed pulses in the lower extremities when compared with the upper extremities. A chest x-ray may display cardiomegaly with a left ventricular hypertrophy configuration. In long standing cases, rib notching due to erosion of the lower anterior portion of the rib by dilated collateral arteries can be appreciated. The echocardiogram demonstrates narrowing of the distal aortic arch with increased velocities on pulsed and color Doppler. The pulsed Doppler waveform has a typical prolonged systolic phase extending throughout systole. The MRI produces a static but clearer picture, than the echocardiogram, of the anatomy of the coarctation. An angiogram is sometimes necessary to clarify associated cardiac lesions.
There are several surgical techniques used to repair a coarctation of the aorta. Each technique has had its own proponents at one time or another. If the coarcted segment is short and discrete, resection and end to end anastomosis of the proximal and distal ends is possible. If the coarctation is a long tubular obstruction, resection with interposition of a tube graft would be necessary. Some surgeons favor a longitudinal incision with insertion of a synthetic graft to enlarge the diameter. In the young infant, sacrificing the left subclavian artery, and using the transected blood vessel as a graft by turning it down and sewing it into the aortic wall was popular at one time (5).
Catheter balloon dilatation of native coarctations has not been as successful as dilatation of postoperative restenosis of a coarctation. The former technique has resulted in late appearance of aneurysms. The use of stents to reinforce the arterial wall is now preferred to balloon dilation alone.
A postoperative complication that is now rare is the syndrome of mesenteric arteritis (6), caused by reflex spasm of mesenteric arteries that are suddenly exposed to higher pressures after the coarctation is removed. The spasm can be severe enough to result in bowel ischemia. Patients are being operated on at a younger age now so that the mesenteric arteries do not have as long a period of exposure to low pressures and are therefore less reactive.
Ventricular septal defects (VSD), atrial septal defects (ASD), and patent ductus arteriosus (PDA) account for a large percentage of all congenital heart defects. They share common physiologic hemodynamics and will be discussed together.
These defects represent abnormal communications between the high pressure left side of the heart and the low pressure right side of the heart. The pressure differential results in a left-to-right shunting of blood through the defect. The consequences of this shunting of blood are: turbulence of abnormal blood flow producing a heart murmur in systole and sometimes in diastole; excessive blood flow into the lungs causing shortness of breath and increased pulmonary vascularity on a chest x-ray; and increased volume overload of the myocardium resulting in hypertrophy of myocardium and chamber dilatation.
The murmur of a VSD is located at the lower left sternal border and is dictated by the anatomic location of the defect in relation to the chest wall. Since flow across the VSD occurs as long as there is a pressure differential between left and right ventricles, the timing of the murmur in this lesion is pansystolic. The high pressure turbulence of the shunted blood produces a harsh quality to the murmur. When the pulmonic flow exceeds the systemic flow by a ratio of 2:1, an apical diastolic murmur is produced due to excessive flow during recirculation across the mitral valve. Frequently, a VSD murmur is not heard at birth (day 1 of life) since pulmonary vascular resistance and pulmonary pressure may still be high, limiting left to right shunting through the VSD. As pulmonary vascular resistance drops further, more left to right shunting through the VSD occurs, making the murmur audible on day 2 or day 3 of life.
The murmur of an ASD is produced by excessive flow across the pulmonic and tricuspid valves resulting in a systolic murmur at the second left intercostal space and a mid-diastolic murmur over the lower right sternal area. Note that this is a flow murmur and NOT a murmur due to turbulent flow across the ASD. Flow across the ASD is low velocity and not turbulent and therefore produces no audible murmur itself.
The flow through a PDA is continuous due to the existence of a constant pressure differential between aorta and pulmonary artery in both systole and diastole. The machinery quality of the murmur results from the rhythmic variation of the pressure differentiation during the cardiac cycle. The location of the murmur is at the upper left sternal border.
A small shunt produces only a murmur but no symptoms. With increasing defect size and pulmonary flow, signs and symptoms of congestive heart failure occur: shortness of breath with exertion and in severe cases, also at rest; cough and susceptibility to pulmonary infections; hepatomegaly, splenomegaly, and lower extremity edema result from retrograde extension of the systemic venous congestion into the liver, spleen and legs.
The chest x-ray in a left-to-right shunt lesion will demonstrate congested pulmonary vessels. Enlargement of specific cardiac chambers is due to excessive volume overload. The left atrium and ventricle are dilated in VSD and PDA, and the right heart chamber is dilated in ASD. The EKG reveals hypertrophy of the corresponding cardiac chambers.
Untreated defects with large shunts will eventually result in injury to the pulmonary arterioles, vascular obstruction, and pulmonary hypertension. The development of permanent injury to the pulmonary vessels is a function of the duration of the exposure to excessive blood flow and the anatomy, occurring more rapidly in VSD and PDA than in ASD. If this process is not reversed, Eisenmenger's complex of right to left shunting may occur as the right sided pressures (pulmonary hypertension) exceeds left sided pressures.
Intracardiac repair of a VSD and ASD require cardiopulmonary bypass. Repair of a PDA is extracardiac and is achieved without cardiopulmonary bypass. The intracardiac defects can be closed by primary suturing of the edges of the defect if small, or by covering with a patch material if large. The PDA is usually tied off and divided.
Complete heart block secondary to injury to the conduction system during repair of a VSD may require a pacemaker in the postoperative period. The knowledge of the location of the conduction system in relationship to the defect now makes this a rare complication. The mortality rate in experienced hands should be less than 5% if all ages are considered, with infants carrying a higher mortality rate especially if pulmonary hypertension is present.
1. True/False: Congenital heart disease is always detectable at birth.
2. True/False: Equal blood pressures in the right arm and left leg rule out the diagnosis of coarctation of the aorta.
3. Which are the three most common acyanotic congenital heart lesions?
4. True/False: The presence of palpable femoral pulses rules out the diagnosis of aortic coarctation.
5. True/False: Surgical repair of PDA does not require cardiopulmonary bypass.
6. Explain how a child with an isolated VSD (classified as an acyanotic lesion) could become cyanotic?
7. True/False: Medical students and residents will typically not hear the murmur of a VSD during the initial newborn assessment in the nursery because the murmur of a VSD is subtle and low pitched.
Aortic Coarctation: Goto CS. Wheezing and Respiratory Distress in a 7-Week Old. In: Yamamoto LG, Inaba AS, DiMauro R. Radiology Cases In Pediatric Emergency Medicine, 1995, volume 2, case 6. Available online at: www.hawaii.edu/medicine/pediatrics/pemxray/v2c06.html
Cor Triatriatum: Matsuda JJ. Tachypnea in a 2-Month Old. In: Yamamoto LG, Inaba AS, DiMauro R. Radiology Cases In Pediatric Emergency Medicine, 1995, volume 4, case 3. Available online at: www.hawaii.edu/medicine/pediatrics/pemxray/v4c03.html
1. Keith JE, Rowe RD, Vlad P. Incidence. In: Keith JE, Rowe, RD, Vlad P (eds). Heart Disease In Infancy And Childhood, second edition. 1967, New York: The Macmillan Company, p 3.
2. Brom AG. Narrowing of the aortic isthmus and enlargement of the mind. J Thorac Cardiov Surg 1965;50:166.
3. Duffie Jr. ER, Wilson JF. Coarctation of the Aorta. In: Moss AJ, Adams FH (eds). Heart Disease In Infants, Children, and Adolescents, second edition. 1968, Baltimore: The Williams and Wilkins Company, p. 386.
4. Silander T. Anomalous origin of the right subclavian artery and its relation to coarctation of the aorta. Arch Chir Scand 1962;124:412.
5. Waldhausen JA, Nahrwold DL. Repair of coarctation of the aorta with subclavian flap. J Thorac Cardiovasc Surg 1966;51:532-533.
6. Sealy WC. Indications for surgical treatment of coarctation of the aorta. Surg Gynec Obstet 1953;97:301.
Answers to questions
1. False. The physiologic pulmonary hypertension present in a newborn can prevent blood flow across a septal defect or PDA. These can be detected several hours after birth or several days after birth. Other congenital heart disease lesions may remain occult for longer period of time.
2. False. An aberrant right subclavian artery originating below a coarctation will produce equal pressures in the right arm and leg.
3. VSD, ASD, PDA. Of these, VSD is the most common.
4. False. Development of collateral vessels to the lower body can produce palpable femoral pulses.
6. Congestive heart failure and pulmonary edema may cause hypoxia. If the hypoxia is severe enough, visible cyanosis will result, although this can be overcome with oxygen and other treatments for pulmonary edema and congestive heart failure. Long standing excessive pulmonary blood flow leads to pulmonary hypertension and Eisenmenger's complex, right to left shunting and cyanosis.
7. False. They cannot hear the murmur of a VSD on day 1 because on day 1, pulmonary vascular resistance is still high, which restricts left to right flow through the VSD. On day 2, pulmonary vascular resistance is lower, so left to right shunting through the VSD increases making the murmur louder.