The ECG reveals group beating with groups of two and each QRS complex is preceded by a P wave. The P waves are uniform in shape and appear to be of sinus origin. The PR interval of the first beat in each group is 0.20 seconds and that of the second is 0.24 sec. The interval of 1.3 seconds between the groups is less than twice the RR interval of the two beats within each group (0.88 x 2 =1.76). There are no P waves, either sinus or ectopic, between the groups. This is an example of 3:2 SA block with an S-S interval of 0.88 - 0.90 seconds.
The ladder diagram below the tracing depicts sino-atrial (SA) conduction and illustrates the lengthening of the S-A interval prior to the blocked sinus impulse. This defines the rhythm as type 1 2nd degree SA block with Wenckebach periodicity. Note the lengthening of the PR interval in the second beat of each group. This suggests the possibility of type 1 2nd degree AV block as well. This patient is a candidate for cardiac pacing unless there is a reversible cause for the SA block such as treatment with drugs such as digitalis, or unless another cause for the “funny spells” can be determined.