Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content +++ ECG Findings ++ ST-segment depression in leads V1-V3 Upright T waves in V1-V3 Tall R waves with an R-wave/S-wave ratio greater than 1 in lead V1-V3, most often seen in V2-V3, developing over the course of hours +++ Pearls ++ Note that some authors refer to “posterior” infarction as “inferolateral” infarction, based on echocardiographic data that show that the involved portion of the left ventricle in question is actually inferolateral rather than truly posterior in location. This diagnosis is often missed as the posterior portion of the left ventricle has no ECG electrodes directly overlying it. This means that posterior MI will only reflect as reciprocal changes that are most common in V1-V3. Instead of ST elevations, one will find ST depressions, and instead of Q waves, one will see tall R waves. Posterior involvement may be confirmed with posterior leads. V7 is located in the left posterior axillary line; V8 is located at inferior tip of left scapula; V9 is positioned between V8 and the spine, all in the same horizontal plane as V6. Frequently, an inferior MI is also present with a posterior MI, since the right coronary artery serves both areas. ++ FIGURE 23.5A Acute Posterior Myocardial Infarction. (ECG contributor: R. Jason Thurman, MD.) Graphic Jump LocationView Full Size|Favorite Figure|Download Slide (.ppt) ++ FIGURE 23.5B This tracing demonstrates injury in the posterior LV, manifesting as acute ST depression in V2 (arrow). Graphic Jump LocationView Full Size|Favorite Figure|Download Slide (.ppt) ++ FIGURE 23.5C Flipping the ECG upside down and looking through the paper with a backlight shows an ST-elevation injury pattern (arrow). A posterior ECG can help distinguish between posterior STEMI and anterior ischemia. Graphic Jump LocationView Full Size|Favorite Figure|Download Slide (.ppt) ++ FIGURE 23.5D The R-wave amplitude approximates that of the S wave (arrow), and the R-wave duration is significant (>4 ms). This is actually an “inverted Q wave” from a posterior infarction. 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