PMC5420023_01
Presenting 12-lead electrocardiogram.
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Prior to the procedure an electrocardiogram (ECG) (Figure 1) was performed, owing to an irregular pulse. Figure 1 demonstrates her presenting ECG at her ophthalmologist's office upon the ophthalmologist's noticing her pulse to be "irregular." Upon admission, alternating or "grouped beating" and intervals of progressive PR shortening were noted on telemetry.
Continuous rhythm strip.
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Upon return to her room a continuous rhythm strip was performed (Figure 2), which again illustrated progressive PR interval shortening, as previously seen on telemetry.
Fast pathway initially disengaged by a premature ventricular contraction (PVC1), subsequently engaging the slow pathway with the same premature ventricular contraction (PVC1), and reengaging the fast pathway once again (PVC2). Slow pathway conduction demarcated by long PR interval marked by brackets [ ] with transition to fast pathway conduction indicated by asterisks *.
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Close inspection of a repeat ECG (Figure 3) demonstrates abrupt shortening and lengthening of the PR interval ("PR alternans") with engagement and disengagement of the slow and/or fast pathway.