Practice ECG 9
The P waves are notched and measure exactly 0.12 seconds, and the distance between the humps is more than 0.04 seconds. This meets the criteria for P-mitrale. The biphasic P in V1 is also compatible with LAE.
The rhythm is a second-degree Mobitz I (Wenckebach). Note the grouped beats, the lengthening of the PR interval, and the dropped QRS complex after the final P of the group. The grouping is variable, with the third, fourth, and fifth QRS complexes forming one set, and the sixth and seventh forming another. The first and last groups cannot be determined.
The presence of rabbit ears (RSR') in V1 with a QRS width less than 0.12 seconds makes this an incomplete right bundle branch block (IRBBB). This has no clinical relevance except that there is a tendency to progress to a complete RBBB in the future.
The early transition with a Z-axis of 15 degrees anteriorly is highly suggestive of RVH. Infarction is a possibility; an old ECG and clinical correlation would be helpful in making the diagnosis.
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