Drug Abuse Follows a Broken Heart

ANSWER
This ECG shows sinus tachycardia at a rate of 110 beats/min, evidenced by the presence of a P wave for every QRS complex with regular R-R intervals. Left atrial enlargement is evident from the presence of P waves ≥ 110 ms (admittedly difficult to see in this example) and a terminal negativity of the P wave in lead V₁ ≥ 1 mm². A rightward axis is evidenced by the presence of an R-wave axis of 96°; however, it does not meet criteria for a true right-axis deviation 
(≥ 105°). Nonspecific T-wave abnormalities are observed in leads V₅ and V₆. 

The most intriguing aspect of this ECG is observed in lead V₃. Note the abrupt disruption of R-wave progression between leads V₂ and V₄. This was due to incorrect placement of the ECG electrode for V₃, which occurred in the haste to obtain the ECG prior to the CT scan. This illustrates the importance of correct electrode placement for an accurate tracing.