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Patient
83-year-old man, hypertensive treated by beta-blocker, hospitalized in the setting of repeated lightheadedness with a fall; evidence of a prolonged pause during entry electrocardiogram;
Trace
The rhythm is initially sinus (positive P waves in leads II, V5, V6 and negative in aVR, low voltage in lead I) with bradycardia of 43 bpm; narrow QRS; normal QTc interval; occurrence of a prolonged sinus pause of 6 seconds and then resumption of the sinus rhythm with bradycardia of 45 bpm;
Exergue
When in the presence of a paroxysmal bradycardia, two types of diseases must be differentiated: sinus node dysfunction and atrioventricular block; indeed, the presence of a ventricular pause (sudden slowing of the ventricular rate) in an initially sinus patient may result from:
1) a paroxysmal sinus node dysfunction: absence of P waves on the tracing;
2) a complete paroxysmal atrioventricular block: presence of blocked P waves on the tracing.
This patient presents a sinus node dysfunction with presence of paroxysmal, prolonged, symptomatic pauses. The total absence of atrial activity leads to the diagnosis of sinoatrial arrest and not of an atrioventricular block (the pause would have been related to blocked P waves).