1. Counterpoint: M cells do not have a functional role in the ventricular myocardium of the intact heart 
Michiel J. Janse, MD, PhD, Ruben Coronel, MD, PhD, Tobias Opthof, PhD 
Heart Rhythm 
Volume 8, Issue 6, Pages (June 2011)
DOI: /j.hrthm
Copyright © 2011 Heart Rhythm Society Terms and Conditions

2. Figure 1
Top: Strength-interval curves for cathodal stimuli for 9 terminals of an intramural plunge electrode (terminals 2 to 10). Dots indicate the end of the absolute refractory period (ARP), functional refractory period (FRP), and total refractory period (TRP). Bottom: Temporal relation during activation and recovery of excitability (experiment of February 1, 1956). Note early recovery of excitability in midmural layers. Also note that the sum of activation time and refractory period (which corresponds to repolarization time) is longest in the epicardium.
Reproduced with permission from Van Dam and Durrer.4
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions

3. Figure 2
Activation time (AT) versus activation-recovery interval of the canine left ventricle (A) and versus repolarization time (B). C: Activation and repolarization sequence of the same heart. See text for discussion.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions

4. Figure 3
Activation maps of a premature beat (S2). Top: Diagrams. Bottom: Activation map of a perfused pig heart in which a large repolarization gradient was created. See text for discussion.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions