This ECG shows atrial dissociation in a 70-year-old male with a history of hypertension, coronary artery disease, and cardiac transplantation 6 months prior. Atrial dissociation is seen as two independent sets of P waves with varying PP and PR intervals. Atrial dissociation occurs when each atrium beats separately due to blockage of the Bachmann's bundle interatrial pathway. It can occur in orthotopic and heterotopic heart transplant patients as the posterior atrial wall is retained but denervated after orthotopic transplant.

1. ECG OF THE WEEK DR.Prof.K.H.Noorul Ameen’s unit(M4) Dr.S.Dhileepan

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

4. 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.

5. DIAGNOSIS ATRIAL DISSOCIATION

6. Atrial dissociation First reported by Wenkeback in 1906. It has been suggested that in atrial dissociation each atrium beats separately and independently as a result of blockage or interruption of an interatrial pathway (Bachmann's bundle). The sinus pacemaker controls one atrium and the ectopic pacemaker controls the other atrium. The two pacemakers do not interfere with each other as a result of interatrial block or presence of preferential exit block

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

8. causes RHD SHT CCF Sudden neurogenic stimuli Uremia Diphtheria

9. 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.

10. Orthotropic transplantation

11. Heterotropic transplantation

12. Heterotrophic transplantation

15. ECG shows Varying PP,PR,RR interval, P wave inverted and gradually become normal when heart rate speeds up.

16. Wandering pacemaker

17. causes Phyisiologic-deep sleep Young adults with high vagal tone Digitalis Sick sinus syndrome

18. 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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