Practice ECG 7
Here is a patient who was probably in NSR and subsequently developed a junctional rhythm with retrograde conduction of the Ps. Look at the morphology change in II from upright to inverted P waves. Lead aVF shows P waves that are completely negative, representing the junctional origin of the rhythm.
Can you see any reason why he would be developing a junctional rhythm? Are those ST segments in V1 to V5 caused by early repolarization changes? If you answered yes, go back to Chapter 6 (page 44), Chapter 11: ECG 11-29 (pages 215-216), and the beginning of Chapter 14 (page 310) in your textbook and review the concept. If you thought they were secondary to a big anteroseptal MI with lateral extension, proceed to the next ECG.
This ECG captures the rhythm change beautifully. What is the cause of the rhythm change in this patient? We would have to say ischemia, ischemia, ischemia! We hope you were able to see the small (sarcastically written for your amusement) ST elevation in V1 to V5 associated with Q waves in V1 to V4.
Does the height of the ST segment correlate with the size of the infarct? No. You can have a relatively small infarct with large ST segment changes or vice versa. The key is that any infarct is bad.
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