left posterior fascicular block

It is much more common than left posterior fascicular block.

Left posterior fascicular block.

There are also partial blocks of the left bundle branch: "left anterior fascicular block" (LAFB) and a "left posterior fascicular block" (LPFB).

A left posterior fascicular block (LPFB) is a condition where the left posterior fascicle, i.e. the backside part of the left cardiac bundle, does not conduct the electrical impulses from the atrioventricular node.

A subset of individuals with the triad of first-degree heart block, right bundle branch block, and either left anterior fascicular block or left posterior fascicular block (known as trifascicular block) may be at an increased risk of progression to complete heart block.