This ECG shows a 58-year-old female patient who presented with chest pain. The ECG reveals sinus rhythm with 5:4 second-degree sinoatrial exit block, where every fifth impulse is blocked at the SA junction. This type of SA block is characterized by no change in P-R interval before the pause and a pause interval that equals approximately two to four times the normal P-P cycle length. SA node dysfunction can be intrinsic, due to degenerative causes like fibrosis, or extrinsic, due to autonomic influences or drugs that suppress the SA node. Diagnosis is usually clinical or via ECG and pacemaker implantation may be indicated for symptomatic patients.

1. Prof.S.SUNDAR’s unit Dr.G.Rengaraj.PG ECG OF THE WEEK

4. Rhythm strip

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