Figure 7. Fractionated upstroke of the optical action potentials indicated two distinct tissue layers.

(A) Upstroke during sinus rhythm (SR) and induced by stimulation (Stim). (B) Vertical alignment of optical action potentials on the dorsal side of the alligator heart. (C) Principle component analysis (PCA) illustrating the different morphology of the upstroke with and without fractionation. (D) shows local electrograms recorded from the dorsal and ventral side of the heart shown in Figure 7—figure supplement 1. (E-F) In vivo heating of anaesthetized 2-year-old alligators leads to an increase in heart rate and a decrease in ventricular activation time as assessed by QRS duration (points are averages, error bars are standard deviation). The QRS duration of warm alligators never approach the much shorter QRS duration of eutherian mammals (Detweiler, 2010).

Figure 7—figure supplement 1.

(A) Activation maps from the dorsal and ventral surfaces of the ventricle based on the first and second deflection of the upstroke. (B) Representative optical action potentials used in A. This figure is based on a typical example. LV, left ventricle; RV, right ventricle; OFT, outflow tract.