2:1 AV block is a form of second-degree AV block that can be type I or type II. If the PR interval of the conducted beat is prolonged and the QRS complex is narrow, then it is most likely second ...

The one case of second/third-degree and two cases of third-degree AV block were diagnosed by urgent echocardiogram more than 17 to 72 hours from a previously normal FHRM episode.