Page 175 - Clinical Pearls in Cardiology

Ischemic Heart Disease 163

an ectopic rhythm with three or more consecutive
premature ventricular beats at a rate faster than the
normal ventricular intrinsic escape rate of 30 to 40 beats/
minute, but slower than that of classical VT (i.e 100 to
120 beats/minute). The occurrence of slow ventricular
tachycardia or AIVR in patients with acute myocardial
infarction is considered as a specific marker of successful
reperfusion following thrombolysis.
15. What is tachycardia-bradycardia syndrome?
Sick sinus syndrome comprises a variety of conditions
involving sinus node dysfunction and commonly affects
elderly persons. Sick sinus syndrome has multiple
manifestations on electrocardiogram, including sinus
bradycardia, sinus arrest, sinoatrial block and the
tachycardia-bradycardia syndrome. The tachycardia-
bradycardia syndrome is a common manifestation of
sinus node dysfunction where episodes of paroxysmal
atrial fibrillation, flutter or tachycardia are followed
by severe sinus bradycardia, sinoatrial block or sinus
arrest, resulting in symptoms of low cardiac output (e.g.
dizziness, confusion, fatigue, Stokes-Adams attacks, heart
failure, etc). The diagnosis of the ‘sick sinus syndrome’
is made if there is less than a 25% increase in heart rate
with intravenous atropine (the normal response is an
increase in heart rate by 50–60%). Treatment for this
disorder, if symptomatic, usually requires a pacemaker,
although initial management with theophylline 200–400
mg/day may be of benefit.
16. How do you differentiate between broad complex
tachyarrhythmias?
When confronted with a patient who has palpitation
and a tachyarrhythmia with a broad QRS complex,
it is important that we differentiate between a