Cardiovascular
Medicine - Education Center
Sinus bradycardia:
In sinus bradycardia, the heart rate is
below 60 beats/min and each QRS complex is preceded by a P wave.
This
is usually associated with respiratory sinus arrhythmia. It occurs as
a normal phenomenon in athletes. Sinus bradycardia is accentuated by
digitalis and vagotonic procedures such as carotid sinus compression.
It may also be associated with myxedema, obstructive jaundice (direct effect of bile salts
on the sino-atrial node), uremia,
increased intracranial pressure and glaucoma (increased and persistent oculocardiac reflex).
The administration of beta-blockers is a common iatrogenic cause. After these causes have been
excluded, the presence of structural sino-atrial node disease must be considered since this may be one of
the manifestations of the "sick sinus syndrome".
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