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 MyAccess 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 Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth