Atrial Arrhythmias

Atrial Fibrillation

– Chaotic irregularly irregular rhythm
– Either no P waves or coarse fibrillatory P waves that can be seen in V1
– Narrow QRS complex < 120ms unless pre-existing bundle branch block, accessory pathway, or rate-related aberrant conduction
– Variable R-R interval
– Ventricular rate usually ranges from 80 to 180 BPM

Atrial Flutter

– Regular rhythm
– Narrow complex tachycardia, QRS < 120 ms
– Ventricular rate depends on conduction ratio and degree of AV block such as 2:1 (most common) or 3:1, 4:1 etc

Typical atrial flutter or Type I atrial flutter (Anticlockwise reentry)

Typical atrial flutter or Type I atrial flutter (Clockwise reentry)

Atypical atrial flutter or Type II atrial flutter

Atrial Premature Beat

– Non-sinus, morphologically different P waves
– Shorter P-P interval compared to previously normal P-P of sinus beat as PAC occur prematurely
– Usually followed by a normal QRS complex (< 120 ms) or mostly RBBB pattern if aberrantly conducted
– Identical PACs originate from single focus in the atrium
– Multiple P-wave morphologies indicated > 2 foci of origin
– PACs can present as bigemini, trigemini and so on based on their frequency

Focal Atrial Tachycardia

– Arise from a single site within the left or right atrium outside the SA node
– Atrial rate during focal AT is between 110 and 250 BPM
– P waves are assessed in lead V1 and lead II. All P waves are identical (unifocal)
– Left atrium origin: +ve P wave in V1 or biphasic with an initial negative deflection
– Right atrium origin: -ve P wave in V1 or biphasic with an initial positive deflection
– AV conduction is 1:1 (every P wave is followed by QRS)
– QRS is usually narrow unless beat is aberrantly conducted

Multifocal Atrial Tachycardia

– P waves have >= 3 forms
– Atrial rate: 100 to 200 bpm
– Irregular rhythm
– Variable P-P interval, P-R duration, and R-R interval
– Isoelectric baseline between P waves
– Differential: Afib with coarse P waves, Aflutter with variable block, sinus tach with frequent PACs

Sinus tachycardia

– Heart rate > 100 BPM
– Sinus, upright P waves in lead I and II
– Normal PR interval and QRS duration
– Regular rhythm

Sinus Bradycardia

– A resting heart rate of 60 beats per minute or less
– Sinus rhythm with upright and regular P waves
Regular rhythm