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Practice 12-Lead ECG #1
Practice ECG 1 (click for a larger image):
Take a look at the ECG and try to figure out what is going on with the P waves. In the review ECGs, we want you to try to make determinations for yourself and then look up the answers to verify your findings.
Have you isolated the P waves? Have you looked at them closely in all leads? Do you remember the leads in which the P wave is supposed to be positive, and the one in which it should be negative? If you don't recall, go back and review the concept in Chapter 9. In this ECG, the P waves are abnormal in leads II, III, and aVF. We saw one of these rhythms before. This is a junctional rhythm with retrograde conduction of the P waves, which appear before the QRS complexes.
The patient has slurred S waves in leads I and V6 as well as an RSR'-like complex in V1. The problem is that the first R wave is missing. This is because the R wave was lost due to a Q-wave infarct. The result is a QR' complex, not an RSR'. Because of an old anteroseptal AMI, the poor rabbit cannot keep his right ear up and it flops over. Remember that the morphology of the RSR' complex in V1 can vary greatly, as we see in this example. Make the diagnosis of RBBB by looking at the slurred S waves in leads I and V6 primarily, and then for the rabbit ears-or at least a positive complex-in V1.