The incomplete left bundle branch block.

(ILBBB) has received scant attention in the literature as an elec-trocardiographic entity, seemingly due to its multiple etiologies and its superficial resemblance to left ventricular preponderance (LVP) ,** and left ventricular is-chemia. In a review of current texts, Fried-berg,1 Lipman and Massie,2 Wolff3 and Levine4 stress the difficulty in electrocardio-graphically differentiating the ILBBB from left ventricular hypertrophy (LVH). Grant' questions it as an electrocardio-graphic entity and Goldberger6 and Plotz7 fail to describe it. It is hoped that these current data, supported by a review of previous pertinent works,'' " will more firmly establish the ILBBB as a fairly common electrocardio-graphic pattern. Most certainly, it is a frequent cause for electrocardiographic misinterpretation .