Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ ECG Findings ++ QRS duration normal or slightly prolonged Right axis deviation (without any other reasons for rightward axis on ECG) Small R wave and large S wave in the lateral leads (I, aVL) Small Q with a large R wave in the inferior leads (II, III, aVF) +++ Pearls ++ In left posterior fascicular block (LPFB) the conduction through the left posterior fascicle is blocked, which causes the conduction of the inferior portion of the left ventricle to occur in a delayed fashion, as conduction spreads from the intact left anterior fascicle and the right bundle branch. This causes a typical rightward axis deviation. In contrast to the LAFB, this is rarely a normal variant. The posterior fascicle receives its blood supply from both the left coronary and right coronary arteries; hence, if an LPFB is present, this may indicate multi vessel coronary artery disease. ++ FIGURE 23.22A Left Posterior Fascicular Block. (ECG contributor: James V. Ritchie, MD.) Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ FIGURE 23.22B Small R waves and large S waves in leads I and aVL (arrows). Graphic Jump LocationView Full Size||Download Slide (.ppt) Your Access profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free a profile for additional features.