The patient presented with chest pain for 3 hours and a history of hypertension. An ECG showed an atrial rhythm originating from the coronary sinus with a heart rate of 100 bpm and inverted P waves in leads II, III, and aVF. The diagnosis was a coronary sinus rhythm with an inferior-posterior wall myocardial infarction based on ST elevations in leads II, III, and aVF with T wave inversions and ST depressions in leads V2-V4.

1. ECG of the week By Dr. C. R. Rajakumar M5 unit Prof. P. Vijayaraghavan’s unit

2. Patient presented with c/o Chest pain for the past 3 hrs He was a known hypertensive on drugs for the past 5yrs. ECG was taken

4. ECG findings Heart rate 100 per minute. Inverted P waves in leads II, III, aVF. PR interval 140ms (3 ½ small squares) QRS Duration normal Axis 30º ST elevation in II, III, aVF (III>II) with T wave inversion ST depression in V2-V4 with tall R and upright T wave

5. Diagnosis Coronary sinus rhythm with Infero posterior wall MI

6. Atrial Rhythms Atrial rhythm resembles sinus rhythm, but origins from a different atrial focus. It can be recognised by the abnormal configuration of the p-wave

7. Characteristics of atrial rhythm Atrial Rhythms Atrial frequency 50 – 100 bpm Ventricular frequency 1:1 Regularity Regular Origin Atrium P wave Present but differs form sinus rhythm Effect of adenosine Slows down

8. FREQUENCY OF ECTOPIC SITE

9. Frequency of atrial ectopic sites

10. Algorithm to identify site of atrial rhythm

11. Coronary sinus rhythm; inverted p waves in lead 2 ,3 aVF and PR interval normal

12. Which chamber? Right atrial A negative or biphasic (positive, then negative) P-wave in lead V 1 was associated with a 100% specificity for a tachycardia arising from the RA. Left atrial A positive or biphasic (negative, then positive) P-wave in lead V 1 was associated with a 100% sensitivity for a tachycardia originating in the LA.

13. Superior or inferior location of ectopic impulse? In general, the polarity of leads II, III, aVF is deeply negative for an inferiorly located ectopic impulse. Low amplitude, positive, or biphasic for a superiorly located ectopic impulse.