ECG: Atrial Dissociation

ECG OF THE WEEK

DR.Prof.K.H.Noorul Ameen’s unit(M4)

Dr.S.Dhileepan

History

• 70 yr old male,• k/c HT,CAD for 20 years,• Had cardiac transplantation 6 months back.

ECG shows

• HR-140/min,• Rhythm –regular,• PR interval -0.28 sec,• Axis +60-90 degree,• Incomplete RBBB• Two sets of P waves, independent to each

other and one being always conducted.

DIAGNOSIS

ATRIAL DISSOCIATION

Atrial dissociation

• First reported by Wenkeback in 1906. It has been suggested that inatrial dissociation each atrium beats separatelyand independently as a result of blockage orinterruption of an interatrial pathway (Bachmann'sbundle). The sinus pacemaker controlsone atrium and the ectopic pacemaker controlsthe other atrium. The two pacemakers donot interfere with each other as a result of interatrial block or presence of preferential exit block

Differential diagnosis

1)Atrial parasystole-conducted, - normal P wave.2)Artefact –rhythmic muscular twitchings, electrical disturbance from adjacent person.

causes

• RHD• SHT• CCF• Sudden neurogenic stimuli• Uremia• Diphtheria

Atrial dissociation in transplanted heart

• Heart transplantation- orthotropic, - heterotropic . • In orthotropic transplantation posterior wall

of recipient heart is retained but denervated.• It produces impulse but not conducted as it is

blocked by suture line.• In heterotrophic transplantation 2 sets of

complexes are produced.

Orthotropic transplantation

Heterotropic transplantation

Heterotrophic transplantation

ECG shows

• Varying PP,PR,RR interval,• P wave inverted and gradually become normal

when heart rate speeds up.

Wandering pacemaker

causes

• Phyisiologic-deep sleep• Young adults with high vagal tone• Digitalis • Sick sinus syndrome

WANDERING PACEMAKER.

• This variant of sinus arrhythmia involves passive transfer of the dominant pacemaker focus from the sinus node to latent pacemakers that have the next highest degree of automaticity located in other atrial sites (usually lower in the crista terminalis) or in AV junctional tissue. The change occurs in a gradual fashion over the duration of several beats; thus, only one pacemaker at a time controls the rhythm, in sharp contrast to AV dissociation.

• Precursor of MAT

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