Pediatric Examination and Board Review (8 page)

17.
(A)
The most common cause of congenital complete AV block is maternal lupus. The pathogenesis is thought to be a result of maternal transfer of lupus antibodies (anti-Ro or anti-La) to the fetus and subsequent damage of the developing conduction system. In patients with congenital AV block, the chances of their mother having anti-Ro or anti-La antibodies are approximately 60-70%. For mothers with lupus, there is a 5% incidence of having a child with complete AV block. Other causes of AV block in the neonate include structural heart disease, myocarditis, and metabolic disease.

18.
(A)
In patients with congenital AV block and symptomatic bradycardia, the treatment of choice is pacemaker implantation. No other therapy has been shown to affect long-term outcome in these patients. Medications are not consistently effective for prevention of bradycardia and therefore are not recommended for chronic therapy. Other indications for pacemaker implantation in patients with complete heart block include a wide QRS escape rhythm, a prolonged QT interval, an asymptomatic infant with a heart rate less than 55 bpm, an asymptomatic child with a heart rate less than 50 bpm, and asymptomatic complete heart block with a heart rate less than 75 bpm associated with congenital heart disease.

19.
(C)
The ECG in
Figure 2-7
demonstrates a prolonged QT interval. The QT interval is usually corrected for heart rate (QTc) and normal limits vary with age and gender. Palpitations associated with this ECG would most likely be a result of a polymorphic ventricular tachycardia known as torsades de pointes. The ventricular arrhythmia may be selflimited or result in symptoms of dizziness, syncope, or death. The occurrence of torsades de pointes is associated with exercise or activity; however, in some cases it may occur at rest.

20.
(D)
Congenital long QT syndrome is most commonly inherited in an autosomal dominant manner (Romano-Ward). It is a result of a defect in 1 of 5 known genes that affect potassium and sodium ion channels in the heart. A specific gene defect has been identified in 50% of patients with clinical long QT syndrome. A less common mode of inheritance is autosomal recessive (Jervell and Lange-Nielsen syndrome). In these patients, there is often associated conductive hearing loss and a higher risk for ventricular arrhythmias and sudden death. Finally, some cases of congenital long QT syndrome occur because of spontaneous mutations. The risk for sudden death in patients with long QT syndrome who present with symptoms of dizziness or syncope is approximately 20% in 1 year, if untreated. The use of beta-blockers decreases the risk of sudden death to < 5%. Therefore, beta-blockers have become the mainstay of therapy as well as avoidance of strenuous activities, especially swimming. Pacemaker implantation is occasionally required for patients with either baseline bradycardia or those who develop bradycardia following treatment with betablockers. Implantable cardioverter defibrillators are now used more frequently in patients who continue to become symptomatic despite medical therapy with a beta-blocker or for those in whom there is a strong family history of sudden death.

21.
(B)
Acquired long QT syndrome can occur with head trauma, myocardial infarction, cardiomyopathy, or as a result of drugs or medications. This list of drugs/medications associated with the acquired prolonged QT syndrome is extensive and updated regularly. Some of the more common medications on this list include amitriptyline or other tricyclic antidepressants, erythromycin, and cisapride.

S
UGGESTED
R
EADING

Allen HD, Driscoll DJ, Shaddy RE, Feltes TF, eds.
Moss and
Adams Heart Disease in Infants, Children and Adolescents.
7th ed. Philadelphia, PA: Williams and Wilkins; 2007.

Braunwald E, Zipes DP, Libbey P, eds.
Braunwald: Heart Disease: A Textbook of Cardiovascular Medicine.
7th ed. Philadelphia, PA: WB Saunders; 2004.

Keane JF, Fyler DC, Lock JE, eds.
Nadas’ Pediatric Cardiology.
2nd ed. Philadelphia, PA: Hanley and Belfus; 2006.

Park M, ed.
Pediatric Cardiology for Practitioners.
5th ed. St. Louis, MO: Mosby; 2007.

CASE 3: A 7-YEAR-OLD WITH A HEART MURMUR

A 7-year-old boy with no significant past medical history is noted to have a heart murmur heard for the first time during a routine physical evaluation by his lifelong pediatrician. The physical examination is significant for a grade 2/6 vibratory systolic murmur heard best at the lower left sternal border with no radiation. The remainder of the physical examination is normal.

SELECT THE ONE BEST ANSWER

1.
What is the most likely diagnosis of this heart murmur?

(A) Still murmur

(B) ventricular septal defect

(C) atrial septal defect

(D) peripheral pulmonary stenosis

(E) venous hum

2.
What supporting evidence would help to confirm the diagnosis of an innocent Still murmur?

(A) a fixed, split second heart sound

(B) the murmur is louder in the supine position compared to the sitting or standing position

(C) a diastolic rumble

(D) the murmur is associated with a precordial thrill (grade IV)

(E) radiation to the back and axilla

3.
Which test would not be indicated for this patient at this time?

(A) ECG

(B) echocardiogram

(C) chest radiograph

(D) cardiac catheterization

(E) four extremity blood pressure determination

4.
What would be the appropriate advice to give the family regarding a child with this murmur?

(A) endocarditis prophylaxis is needed

(B) rigorous sports should be avoided

(C) sports participation is allowable

(D) annual echocardiograms are required

(E) other family members should be screened for heart disease

5.
A 6-week-old infant presents with a heart murmur and a history of poor feeding, diaphoresis, and tachypnea. On examination, he is playful but tachypneic with a grade 2/6 systolic regurgitant murmur heard best in the mid left sternal border, with hepatomegaly, rales, intermittent wheezes, cool extremities with normal distal pulses, and an active precordium. What is the likely diagnosis of this patient?

(A) chronic lung disease

(B) acute upper respiratory infection

(C) congestive heart failure

(D) dehydration

(E) hyperthyroidism

6.
Which test would not be helpful in evaluating this patient?

(A) an echocardiogram

(B) an ECG

(C) a chest radiograph

(D) a throat culture

(E) a physical examination

7.
What heart lesion is least likely to present with congestive heart failure symptoms and signs at age 6 weeks?

(A) ventricular septal defect

(B) patent ductus arteriosus

(C) atrial septal defect

(D) aortopulmonary window

(E) large coronary artery fistula

8.
Which feature may help to distinguish heart failure from an anomalous left coronary artery arising from the pulmonary artery versus heart failure secondary to a ventricular septal defect?

(A) extreme irritability and crying at the onset of feeding

(B) diaphoresis

(C) weight loss

(D) decreased frequency of wet diapers

(E) tachypnea

9.
Which therapy would not be indicated for the acute management of congestive heart failure because of a left-to-right shunting lesion?

(A) digoxin

(B) oxygen supplementation

(C) dobutamine

(D) furosemide

(E) enalapril

10.
A 2-year-old patient presents with symptoms of heart failure. An echocardiogram demonstrates no intracardiac lesion but a dilated, poorly functioning left ventricle. What is the least likely cause of the dilated cardiomyopathy in this patient?

(A) myocarditis

(B) metabolic disease

(C) idiopathic

(D) myocardial ischemia

(E) tachycardia-induced cardiomyopathy

11.
Which of the following would be supportive evidence of the diagnosis of myocarditis?

(A) an endomyocardial biopsy showing fibrosis

(B) an endomyocardial biopsy showing fibrosis and inflammation

(C) systolic flow murmur

(D) an S3 gallop on cardiac examination

(E) hepatomegaly

12.
What is the most common cause of myocarditis?