Sections View Full Chapter Figures Tables Videos 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|Favorite Figure|Download Slide (.ppt) ++ FIGURE 23.22B Small R waves and large S waves in leads I and aVL (arrows). Graphic Jump LocationView Full Size|Favorite Figure|Download Slide (.ppt) GET ACCESS TO THIS RESOURCE Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth Get Free Access Through Your Institution Contact your institution's library to ask if they subscribe to McGraw-Hill Medical Products. Access My Subscription GET ACCESS TO THIS RESOURCE Subscription Options Pay Per View Timed Access to all of AccessEmergency Medicine 24 Hour $34.95 (USD) Buy Now 48 Hour $54.95 (USD) Buy Now Best Value AccessEmergency Medicine Full Site: One-Year Individual Subscription $595 USD Buy Now View All Subscription Options