Supplemental Figure 3.

(A) Survival curves in rats and humans. (B, C, D) Heart weight, body weight and heart weight/body weight ratio in young (n=6) and old rats (n=6). * shows p value <0.05. (E,F) Bipolar recording from the AV node preparation. (E) Photograph of preparation. Once the His bundle had been identified the other three electrodes were positioned. Electrode 1 was positioned at the site of earliest activation (the SN). Electrode 2 was positioned at the atrial septum, electrode 3 was at the His electrode and electrode 4 was positioned between the coronary sinus and the tricuspid valve annulus. (F) Bipolar recordings from the 4 electrodes marked in E. Earliest activation was at electrode 1 and latest at electrode 4. This represents rapid atrial activation spreading from the SA node (marked with white dashed arrows). At the His signal (electrode 3) there was a discrete pause which was followed by a second smaller sharp deflection. This second deflection is the His signal. The time between the atrial and His signal is the AH interval. Adapted from Temple.¹²