Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ ECG Findings ++ PR interval greater than 200 ms (normal 120-200 ms) with no significant variation in PR intervals between beats. Each P wave is followed by a QRS complex. +++ Pearls ++ This type of heart block usually does not affect heart function and can be considered nonpathologic (especially in athletes or patients with higher vagal tone). First-degree block may also occur due to heart disease (myocarditis, rheumatic fever), drugs (digoxin, amiodarone, β-blockers, calcium channel blockers), or as a normal part of aging. ++ FIGURE 23.14A First-Degree AV Block. (ECG contributor: James V. Ritchie, MD.) Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ FIGURE 23.14B The PR interval is fixed (double arrows) and is longer than 0.2 seconds, or five small blocks. 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 select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process 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 Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in 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 profile for additional features.