Tracing D was recorded a day later. The atrial rate remains about 88 (PP intervals of 0.64-0.68 seconds) but there is now 2:1 AV conduction with a prolonged PR interval (0.24 seconds) in the conducted beats.
Tracing E, recorded 2 days after tracing D, now reveals a slower atrial rate with PP intervals that vary from 0.70 to 0.92 seconds (rate = approximately 70} and type I 2nd degree AV block with Wenckebach periodicity and groups of 4 and 5.