A teacher announced to his pupils that on exactly one of the days of the following school week (Monday through Friday) he would give them a test. But it would be a surprise test; on the evening before the test they would not know that the test would take place the next day. One of the brighter students in the class then argued that the teacher could never give them the test. "It can't be Friday...

Congenital complete AV block (CAVB) affects 1 in 20 000 live-born infants2 and is commonly associated with an immune-related cause associated with maternal collagen vascular disease or structural cardiac disease.3 Other causes of CAVB have been described, including infections, myopathies, and genetic disorders such as the Hunter and Hurler syndromes. Still, the specific cause of CAVB remains el...