Pediatric Examination and Board Review (7 page)

(E) prolonged episode of unconsciousness

15.
Which of the following is true regarding tilt table testing for syncope?

(A) tilt table testing should be performed for every patient with syncope

(B) the results of tilt table testing are highly reproducible for an individual

(C) tilt table testing is reserved for complicated cases where the diagnosis of syncope is uncertain

(D) tilt table testing is useful for predicting response to medications

(E) tilt table testing should be performed before initiation of medical therapy

16.
A newborn baby presents with a heart rate of 45 beats per minute (bpm), a normal blood pressure, and good perfusion. The ECG rhythm strip is shown in
Figure 2-6
. What is the diagnosis?

(A) first-degree AV block

(B) second-degree AV block (type 1)

(C) second-degree AV block (type 2)

(D) third-degree AV block

(E) sinus bradycardia

17.
What is the most likely cause of congenital AV block in newborns?

(A) maternal lupus

(B) maternal rubella

(C) maternal use of lithium

(D) maternal diabetes mellitus

(E) maternal use of alcohol

18.
The patient from Question 16 subsequently develops signs of heart failure with poor perfusion and tachypnea. What is the most appropriate long-term therapy for this patient?

(A) pacemaker implantation

(B) digoxin

(C) theophylline

(D) atropine

(E) caffeine

19.
A 10-year-old patient with history of palpitations is found to have the ECG rhythm strip shown in
Figure 2-7
. What is the most likely diagnosis of the palpitations?

(A) myocardial ischemia

(B) orthodromic reentry tachycardia

(C) ventricular arrhythmias

(D) premature atrial beat

(E) premature junctional beats

FIGURE 2-7.

20.
What are the known modes of inheritance for congenital long QT syndrome?

(A) autosomal recessive inheritance

(B) autosomal dominant inheritance

(C) spontaneous mutation

(D) all of the above

(E) it is not known

21.
Which of the following medications is associated with drug-induced long QT syndrome?

(A) propranolol

(B) amitriptyline

(C) metoclopramide

(D) amoxicillin

(E) ibuprofen

ANSWERS

1.
(C)
Palpitations are a common complaint in young patients reported by 16% of patients in a survey at a large primary care clinic. Palpitations are associated with acute arrhythmias in less than 5% of cases when evaluated with long-term monitoring. Palpitations associated with symptoms of dizziness or syncope or in the setting of a family history of arrhythmias or sudden cardiac death would increase the suspicion of an underlying cardiac disorder. Although the echocardiogram, stress test, and chest radiograph are often used to exclude significant cardiac disease, they are unlikely to determine the specific etiology of the palpitations. In this situation, an event recorder could be used to record an ECG rhythm strip during symptoms. An event recorder is a long-term monitoring device used for patients with symptoms that occur infrequently.

2.
(B)
The ECG in
Figure 2-1
shows normal sinus rhythm with a premature ventricular contraction. Premature ventricular contractions are a less common finding in young patients occurring with an incidence of approximately 5-10%. They are usually benign; however, they may rarely be associated with significant heart disease. Therefore, the evaluation often includes an echocardiogram or stress test to assess for associated cardiac disease. Premature ventricular contractions that are not associated with significant heart disease do not require therapy unless they are associated with significant symptoms of discomfort or palpitations.

3.
(C)
The ECG in
Figure 2-2
shows sinus tachycardia. The more common etiologies of sinus tachycardia at this age include anxiety or emotion, hyperthyroidism, anemia, postural orthostatic tachycardia syndrome, and dehydration. It is the most common cause of palpitations in young patients.

4.
(D)
The ECG in
Figure 2-3
shows sinus arrhythmia. This is a benign finding associated with an irregular heart rhythm heard during auscultation. It may vary with respiration and can be pronounced in children. There is no association with significant heart disease.

5.
(A)
The ECG in
Figure 2-4
demonstrates normal sinus rhythm with a single premature atrial contraction. Premature atrial contractions are a common benign finding in young patients occurring with an incidence of approximately 17-25%. They are usually not associated with significant cardiac disease. Because of the benign nature of the premature atrial contractions, they do not require further investigation.

6.
(A)
The most likely cause of supraventricular tachycardia at this age is orthodromic, reciprocating tachycardia because of an accessory bypass tract (“concealed” in this case based on the normal resting ECG). AV node reentry tachycardia is less common at this age; however, this becomes the predominant mechanism of tachycardia in young adults. Ectopic atrial tachycardia and atrial flutter occur with a low incidence throughout childhood. Atrial flutter is more commonly seen in patients who have congenital heart disease.

7.
(D)
Acceptable therapy for orthodromic, reciprocating tachycardia that occurs because of a concealed bypass tract includes DC cardioversion, IV adenosine, or vagal maneuvers. Other antiarrhythmic drugs such as calcium channel blockers can also be used. The determination of which therapy is used is based on the patient’s clinical status at the time of presentation. In patients with stable tachycardia and vital signs, vagal maneuvers or IV adenosine may be first-line treatment. In patients with unstable tachycardia, DC cardioversion may be the first-line therapy. Of note, IV calcium channel blockers are not recommended for use in infants younger than 1 year of age secondary to an increased risk for hypotension.

8.
(B)
First-line medical therapy for chronic treatment of supraventricular tachycardia includes digoxin, calcium channel blockers, and beta-blockers (eg, atenolol). Amiodarone, flecainide, and sotalol are all effective drugs for treatment of SVT but have a higher incidence of side effects (proarrhythmia). Thus they are usually reserved for cases that are resistant to first-line medications.

9.
(D)
Ectopic atrial tachycardia is a rare tachycardia occurring with an incidence of approximately 10% throughout childhood. In some cases of automatic atrial tachycardia, the heart rate is only slightly higher than sinus rhythm; thus the tachycardia may go undetected for months to years. Patients with ectopic tachycardia are at risk for ventricular dysfunction and heart failure. Unlike orthodromic, reciprocating tachycardia and AV node reentry tachycardia, ectopic atrial tachycardia arises from a single atrial focus that does not depend on the AV node. Therefore, adenosine, vagal maneuvers, and DC cardioversion are ineffective. Appropriate acute therapy includes IV beta-blockers, calcium channel blockers, or amiodarone.

10.
(B)
The ECG in
Figure 2-5
demonstrates ventricular preexcitation (short PR interval and slurred upstroke of the QRS or delta wave) because of an accessory bypass tract. When associated with tachycardia, this is known as the Wolff-Parkinson-White (WPW) syndrome. The incidence of WPW syndrome is approximately 0.3%. The mechanism of tachycardia is orthodromic, reciprocating tachycardia similar to that in patients with concealed bypass tracts.

11.
(A)
There is an increased risk of sudden cardiac death (approximately 1 in 1000 patient-years) in WPW syndrome. Sudden cardiac death occurs because of rapid conduction over the accessory bypass tract during atrial tachycardia resulting in ventricular compromise. Patients with WPW syndrome are not at increased risk for ectopic atrial tachycardia or tachycardia-induced cardiomyopathy, but there is an increased incidence of atrial fibrillation in this population.

12.
(C)
First-line chronic medical therapy for patients with WPW syndrome includes beta-blockers or other antiarrhythmic medications such as flecainide or amiodarone. The use of digoxin and/or verapamil is contraindicated in these patients because these agents may potentiate rapid antegrade conduction over the accessory pathway and may increase the risk for sudden death.

13.
(D)
The most common etiology of syncope in young patients is neurocardiogenic or vasovagal syncope. This occurs in up to 20% of the population. Other possibilities include neurologic (eg, seizures), metabolic (eg, anemia, dehydration), or cardiac (eg, arrhythmia) causes.

14.
(D)
Typical features of neurocardiogenic syncope include preceding symptoms of nausea, dizziness, diaphoresis, or blurred vision. The episodes are related to position and usually occur when sitting or standing. Loss of consciousness is brief and resolves spontaneously. The other features mentioned are suggestive of syncope because of a seizure.

15.
(C)
Tilt table testing (
Figure 2-8
) is a simple test used to reproduce neurocardiogenic syncope. However, the low sensitivity and specificity as well as the lack of reproducibility of the test limit its usefulness. It is usually reserved for difficult situations where the etiology of syncope is uncertain. It is not recommended for all patients with syncope and is not useful for predicting response to medications.

FIGURE 2-8.
Tilt table with footboard support. (Reproduced, with permission, from Prystowsky EN, Klein GT. Cardiac Arrhythmias: An Integrated Approach for the Clinician. New York: McGraw-Hill; 1994:353.)

16.
(D)
The ECG rhythm strip in
Figure 2-6
demonstrates third-degree AV block. This is defined as complete dissociation of the atrial and ventricular electrical activity.