34.The answer is b.(Zareba, 2005.)Long QT syndrome (LQTS) is a con-
genital disorder characterized by a prolongation of the QT interval on ECG
and a propensity to ventricular tachydysrhythmias, which may lead to syn-
cope, cardiac arrest, or sudden death in otherwise healthy individuals. The
QT interval on the ECG, measured from the beginning of the QRS complex
to the end of the T wave, represents the duration of activation and recovery
of the ventricular myocardium. In general, HR corrected QTc values above
440 msec are considered abnormal. LQTS has been recognized as the
Romano-Ward syndrome (ie, familial occurrence with autosomal dominant
inheritance, QT prolongation, and ventricular tachydysrhythmias) or the
Jervell and Lang-Nielsen syndrome (ie, familial occurrence with autosomal
recessive inheritance, congenital deafness, QT prolongation, and ventricu-
lar arrhythmias). Patients with LQTS usually are diagnosed after a cardiac
event (eg, syncope, cardiac arrest) already has occurred. In some situations,
LQTS is diagnosed after sudden death in family members. Some individuals
are diagnosed with LQTS based on an ECG showing QT prolongation.
β-Blockers are drugs of choice for patients with LQTS. The protective effect
ofβ-blockers is related to their adrenergic blockade diminishing the risk of
cardiac arrhythmias. Implantation of cardioverter-defibrillators appears to
be the most effective therapy for high-risk patients.
(a)WPW Syndrome is characterized by a shortened PR interval
(< 120 msec), a slurred upstroke of the QRS complex (delta wave), and a
wide QRS complex (> 120 msec). It is caused by an accessory pathway (bun-
dle of Kent) that predisposes individuals to tachydysrhythmias. (c)LGL syn-
drome is classified as a preexcitation syndrome (similar to WPW) in which a
bypass tract is present. LGL is characterized by an individual who is prone to
tachydysrhythmias and has a PR interval less than 120 msec. Unlike WPW,
the QRS complex is normal (no delta wave). (d)Complete heart block is
characterized by the absent conduction of all atrial impulses resulting in
complete electrical and mechanical AV dissociation. (e)Atrial flutter is dis-
tinguished by a sawtooth pattern seen on ECG. It is typically a transitional
rhythm between sinus rhythm and atrial fibrillation.
35.The answer is d.(Tintinalli, pp 136-138.)Automatic implantable
cardioverter—defibrillators (AICD) are placed in patients who are at high
risk for fatal dysrhythmias (eg, ventricular tachycardia and fibrillation) and
sudden death. In these patients, AICDs decrease the risk of sudden death
from approximately 40% per year to less than 2% per year. Occasionally, it
may become necessary to temporarily deactivate an AICD, as in the case of
42 Emergency Medicine