Another example of atrial flutter with group beating is shown here. In this example, the flutter rate is 270 and there are repetitive groups of three QRS complexes. This is explained by 2:1 block in the upper portion of the AV node and 4:3 block in the lower. As in the other examples of type 1 2nd degree AV bloc, the duration of the RR interval enveloping the pause (0.80 seconds) is less than twice the preceding RR interval (2 x 0.44 = 0.88 seconds).