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All ECG 60

There are regular P waves at a rate of 60 beats per minute. The QRS complexes show “grouped beating.” Three of the first four P waves are conducted with increasing PR intervals; the first beat is conducted with a right bundle branch block (RBBB)/left anterior fascicular block (LAFB) pattern; the others show only RBBB. The 4 beat is not conducted (blocked). This is consistent with type 1 second-degree atrioventricular block (4:3). P waves 5, 6, and 7 show a similar pattern with a relatively short PR conducted with RBBB/LAFB, a longer PR conducted with only RBBB, and then a blocked beat (3:2). The final complex shows 2:1 block.

Related Topic Reviews: Second Degree Type I AV Block, Right Bundle Branch Block, Left Anterior Fasicular Block, Left Atrial Enlargement