Medicine C.V.S a0321efd Wenckebachk phenomenon is defined as - A Progressive lengthening of PR B Slurred QRS complex C Irregular hea rate & permature ventricular beats D Shoened ST intervals High-Yield Explanation wenkebach phenomenon is the progressive lengthening of PR i nterval seen in mobitz type 1 AV block. Ref Harrison 20th edition pg 1436