Use of calipers to assess heart rhythm Use of calipers to assess heart rhythm. Note that once the R-R interval is obtained the calipers are simply “marched out” across the tops of the remaining R waves. This ECG reflects a grossly irregular rhythm. (Used with permission from J. Huff, ECG Workout: Exercises in Arrhythmia Interpretation, 3rd ed., Lippincott Williams & Wilkins, 1997.) Source: Chapter 11. Electrocardiography, Cardiovascular and Pulmonary Physical Therapy: An Evidence-Based Approach, 2e Citation: DeTurk WE, Cahalin LP. Cardiovascular and Pulmonary Physical Therapy: An Evidence-Based Approach, 2e; 2011 Available at: https://accessphysiotherapy.mhmedical.com/DownloadImage.aspx?image=/data/books/detu2/detu2_c011f006.jpg&sec=39699175&BookID=456&ChapterSecID=39695854&imagename= Accessed: November 01, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved