Congenital Complete Heart Block



Pediatric Radiology

Radiographic Findings in 13 Patients Without Associated Defects1 Richard B. Jaffe, M.D., Stephen A. Sherman, M.D., Virgil R. Condon, M.D., Richard E. Romm, M.D., and L. George Veasy, M.D. The radiographic findings in 13 patients with congenital complete heart block without associated anomalies arepresented to illustrate characteristic features. Findings related to the increased stroke volume inthese patients include: (a) simulated shunt vasculature; (b) pulmonary venous hypertension with redistribution of blood flowto the upper lungs, and, inone patient, peribronchial edema; (c) cardiomegaly with right ventricular, pulmonary artery, leftatrial, leftventricular, and aortic enlargement; and (d) variation incardiac size onserial examinations. Less commonly seen were findings related to atrioventricular dissociation with transitory, markedpulmonary venous hypertension present in one patient when left atrial contraction occurred during ventricular systole when themitral valve was closed. INDEX TERMS: Heert.abnormaunes s (Heart, congenital heart block 5[1].1938). Heart, flow dynamics • Heart, valves • Heart, volume Radiology 121:435-439, November 1976





ONGENITAL COMPLETE HEART BLOCK (CCHB) is an uncommon problem of infancy and childhood. but its characteristic radiographic features should be familiar to both pediatricians and radiologists. The radiographic abnormalities noted in this condition are a direct consequence of the hemodynamic alterations and are of interest as they represent the physiologic effects of a pure conduction disturbance without accompanying cardiac disease as is generally encountered in patients with acquired heart block. This study reviews 13 patients with CCHB without associated defects to emphasize typical radiographic features, some previously not reported or discussed.

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PATHOPHYSIOLOGY AND HEMODYNAMIC FINDINGS

Two basic abnormalities can be recognized when studying the electrocardiograms of patients with CCHB: marked ventricular bradycardia and atrioventricular dissociation (Fig. 1). Ventricular rates range from 40 to 100 per minute. The bradycardia present in the neonatal period becomes more pronounced as the patient becomes older (3). Despite these intrinsic abnormalities the cardiac output in CCHB is usually normal (1, 4). The most significant physiologic consequences of ventricular bradycardia are the development of increased stroke volume and increased end diastolic heart volume. The increased stroke volume causes the systolic murmur described in this disorder, and the increased end diastolic heart volume is responsible for the frequently observed cardiomegaly with ventricular enlargement (4). A compensatory response is thus established in which there is ventricular bradycardia and an increased diastolic filling period resulting in an 'increase in end diastolic volume with stretching of the myocardial fibers and augmentation of myocardial contractility (5). The increased stroke volume generated through both the systemic and pulmonary circulatory systems results in elevation of right and left ventricular systolic pressure,

Fig. 1. Electrocardiogram, phonocardiogram, and jugular venous pulse tracing ofpatient with CCHB block. The electrocardiogram (EKG) illustrates atrioventricular dissociation with bradycardia (ventricular rate 38 per minute). The phonocardiogram (middle tracing) atthelower left sternal border demonstrates thevariable firstheart sound (1) and the systolic ejection murmur (SM), both characteristic findings. The jugular venous pulse tracing (JVP) illustrates the intermittant "cannon wavf3s" (arrow) present when atrial contraction occurs during ventricular systole when the atrioventricular valve is closed.

pulmonary and systemic systolic arterial pressure, and pulse pressure (4, 5). On occasion, a small gradient may be present between the right ventricle and pulmonary artery. Because of the increased stroke volume through the pulmonary circulation, the normal mitral valve may be too small in relation to the amount of blood attempting to enter the left ventricle in diastole. The pulmonary arterial wedge pressure reflecting the left atrial pressure may be elevated as a result of this "relative mitral stenosis" (1, 2). Certain radiographic features in CCHB result from the presence of atrioventricular dissociation with asynchronous atrial and ventricular contractions. Both right and left atrial pressures are normal, or mildly elevated in congenital heart block (4). The "a" wave of the atrial pulse tracing varies considerably in amplitude. It is maximal if the peak of atrial systole coincides with isovolumic ventricular systole, and during these accentuated periods they are

1 From the Departments of Radiology, University of Utah Medical Center (RB.J., S.A.S.), and Primary Children's Hospital (V.RC.), and Pediatric Cardiology, Primary Children's Hospital (RE.R,L.G.V.), Salt Lake City, Utah. Accepted for publication inJune 1976. shan

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Fig. 2. A three-year-old boy with CCHB. The large stroke volume through the lungs results in large pulmonary arteries and veins simulating shunt vasculature or other high output states. Cardiomegaly with left ventricular and aortic enlargement can also be noted on this frontal radiograph, while right heart and left atrial enlargement was seen on the accompanying lateral film. Fig. 3. Three-year-old girl with CCHB. Chest radiograph demonstrates pulmonary venous hypertension with upper lobe pulmonary venous distension and redistribution of flow. There is slight enlargement of the left atrial appendage,main pulmonary artery and thoracic aorta. Fig. 4. Four-month-old asymptomatic boy with CCHB heart block. Marked pulmonary venous hypertension is present with indistinct vascular margins, peribronchial edema, and a slight amount of fluid in the minor fissure.

known as "cannon waves." "Cannon waves" are responsible for the irregular shock-like pulsations of the neck veins in patients with congenital heart block (Fig. 1).Similar changes may be present in the pulmonary venous circulation when maximal left atrial contraction occurs during left ventricular systole when the mitral valve is closed (4, 5). CLINICAL MATERIAL

Nine girls and 4 boys from the University of Utah Medical Center and Primary Children's Medical Center form the basis of this report. Patients with associated cardiac lesions were excluded, as were those children in whom the complete heart block was thought to be secondary to primary myocardial disease. Age at presentation ranged from newborn to six years. The maximal period of follow-up has been seven years. Seven patients have had a mean follow-up period of four years. None of the children had a history of congestive heart

failure. Two patients presented with a history of syncope, one complicated by documented ventricular fibrillation. No significant extracardiac abnormalities were noted on physical examination. Cardiovascular examination was characterized by bradycardia, greater than normal pulse amplitude, and periodic "cannon waves" in the venous pulsations of the neck. All patients had a grade 2-3/6 systolic ejection type flow murmur maximal at the left sternal border. Variation in the intensity of the first heart sound was also present. Three patients had a diastolic flow murmur along the left sternal border. Resting electrocardiograms revealed complete heart block with atrial rates ranging from 65 to 104 and ventricular rates from 35 to 78 beats per minute. In 4 patients the ventricular rate increased 10 to 20 beats per minute with exercise or crying. One patient required a permanent pacemaker after an episode of ventricular fibrillation. Another patient had placement of a temporary pacemaker prior to an operation.

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Fig. 5. Nine-year-old boy with CCHB. Two chestradiographs document the effects of atrioventricular dissociation on the pulmonary vasculature. An initial chest radiograph reveals striking pulmonaryvenous hypertension and left atrial appendage enlargement, while a repeat radiograph shortly afterwards demonstrates normal pulmonary vasculature and no evidence of left atrial appendage enlargement. Presumably the initial radiograph was taken when atrial systole coincided with ventricular svstole, and as a result maximal left atrial contraction occurred against a closed mitral valve.

p: A[\~OGRAPHIC FINDINGS The radiographic findings in these 13 patients are summarized in TABLE I. Only 2 patients had a completely normal chest radiograph. Large pulmonary arteries and veins simulating shunt vasculature were noted in 4 patients (Fig. 2). Six patients demonstrated pulmonary venous hypertension. Redistribution of pulmonary blood flow to the upper lungs was noted in 4 of these patients (Fig. 3). One asymptornatlc infant had marked pulmonary venous hy-

penenslon with indistinct vessel margins and peribronchial edema (Fig. 4). Of special interest was the demonstration on chest radiographs of transitory marked pulmonary venous hypertension in an eight-year-old boy (Fig. 5). A chest radiograp~ during a routine clinic visit demonstrated marked pulmonary venous hypertension with left atrial and atrial appendage enlargement not consistent with his asymptomatic clinical state and previous chest radiographs. A repoot

Fig. 6. Five-year-old girl with CCHB. A. Prominent pulmonary vasculature and cardiomegaly with biventricular enlargement are present simulating other high cardiac output states such as arteriovenous malformation,anemia,etc. B. Three years after placement of an epicardial pacemaker, therehasbeena marked reduction in cardiac size. Prominent pulmonary vasculature persists with large pulmonary arteries and veins.

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. Fig. 7.

Eleven-month-old boy with CCHB. Two chest radiographs five minutes apart demonstrate a striking variation in cardiac size which stroke volume in these patients. The initial radiograph has recordedthe heart in ventriculardiastole,andthe secondexposure at the end of ventricular systole. IS relatedto the lar~e

Table I: Radiographic Findings in 13 Patients with Congenital Complete Heart Block Normal chest radiograph Simulated shunt vasculature Pulmonary venous hypertension Mild Marked Cardiomegaly Right heart enlargement Main pulmonary artery enlargement Left atria; enlargement Left ventricular enlargement Aortic enlargement Dramatic variation in cardiac size

2 4 6 4 2 8 8 5 6 4 3

radiograph shortly afterwards was normal. Presumably the init!al radiograph was a fortuitous exposure taken when left atrial contraction had occurred during ventricular systole when the mitral valve was closed, resulting in transitory marked pulmonary venous hypertension. Cardiomegaly was noted in 8 of 13 patients (Fig. 6). Right ventricular, main pulmonary artery, and left atrial enlargement was frequently noted. Less commonly seen was left ventricular and aortic enlargement. When comparing serial chest radiographs, variations in cardiac size were common, with the cardiothoracic ratio often varying from 5 to 10% on subsequent examinations. In one patient, a dramatic variation in cardiac size was noted on exposures five minutes apart (Fig. 7). A marked reduction in cardiac size was noted in one patient three years after placement of an epicardial pacemaker (Fig. 6, B). DISCUSSION

The radiographic features of CCHB are a direct reflection of the increased stroke volume and the presence of atrioventricular dissociation seen in this abnormality. More common were those findings related to increased stroke volume. The large stroke volume through the pulmonary

vasculature resulted in the simulation of shunt vasculature on chest radiograph, or other high output states such as anemia or arteriovenous malformation. Pulmonary venous hypertension with upper lobe venous distension was probably secondary to "relative mitral stenosis" (1, 2). Occasionally, the pulmonary venous hypertension was more marked with peribronchial edema present (1). Cardiomegaly was frequently noted with left and/or right ventricular and left atrial enlargement, and was often associated with dilatation of the pulmonary artery and thoracic aorta. These findings are in contrast to those of Eisen et al. (1). who reported pulmonary venous hypertension and cardiomegaly with left ventricular enlargement in their 7 cases of uncomplicated congenital heart block. However, none of their cases showed evidence of "right heart," main pulmonary artery, or left atrial enlargement. The 5 to 10% variation in cardiac size on serial chest radiographs presumably was related to exposures during different phases of the cardiac cycle. The dramatic variation in cardiac size illustrated in Figure 7 demonstates the remarkable volume changes between ventricular diastole and systole as a result of the large stroke volume. Less common, but equally dramatic, were the radiographic abnormalities related to atrioventricular dissociation. Marked pulmonary venous hypertension occurs momentarily when left atrial contraction occurs during left ventricular systole when the mitral valve is closed. Enlargement of the left atrium and atrial appendage becomes more apparent during these periods. Variations in cardiac size on serial examinations also may be related in part to differences in ventricular filling that occur as a consequence of atrioventricular dissociation. ACKNOWLEDGMENTS: The authors wish to thank J. DouglasRidges, M.D., Latter Day Saints Hospital, Salt Lake City, Utah for providing illustrative material used in Figure 1, and Ms. Suzanne L. Key for secretarial assistance.

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REFERENCES 1. Eisen S, Schiebler GL, Elliott LP: The roentgenologic findings in congenital complete heart block without associated defects. Radiology 91:905-909, Nov 1968 2. Jouve A, Gerard R, Torresani J, et al: Les blocs auriculo-ventriculaires conqenitaux complets. Mal Cardiov 7:271-291, 1966 3. Nakamura FF, Nadas AS: Complete heart block in infants and children. New Engl J Med 270:1261-1268,11 Jun 1964 4. Paul MH, Rudolph AM, Nadas AS: Congenital complete atrio-

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ventricular block: problems of clinical assessment. Circulation 18: 183-190, Aug 1958 5. Scarpelli EM, Rudolph AM: The hemodynamics of congenital heart block. Prog Cardiovasc Dis 6:327-342, Jan 1964

Richard B. Jaffe, M.D. Department of Radiology University of Utah Medical Center Salt Lake City, Utah 84132

Congenital complete heart block. Radiographic findings in 13 patients without associated defects.

• Congenital Complete Heart Block • Pediatric Radiology Radiographic Findings in 13 Patients Without Associated Defects1 Richard B. Jaffe, M.D., S...
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