Figure 3.

A: Intracardiac electrophysiology study was used to determine the SAN function. Representative ECG recordings (B) and quantification of corrected SAN recovery time (cSNRT, corrected by intrinsic CL= cycle length) (C). D: Histogram of the circadian oscillation of heart rate during day (left) and night (right). Individual standard derivation of heart rate was used as a measure of heart rate variability (HRV). N = 10 animals in each group. E: Survival analysis of control and HFpEF rats until 18 weeks of age. F: Representative image of electrodes placement surrounding the ex vivo SAN/atrial tissue loaded with a voltage-sensitive dye (left). Overdriving suppression of SAN for assessing the cSNRT was achieved by rapid pacing from the right atrium (RA). cSNRT was quantified before (baseline) and after treatment with adenosine (1 μM) for 10 min (middle). Representative optical action potential traces during RA pacing and time taken to recover the sinus rhythm (right). G: Overview of HFpEF SAN maps uncover the presence of conduction blocks. Data are expressed as mean ± SEM. Unpaired Student t-test (C and D). Log-rank test (E). RM-ANOVA followed by Bonferroni post hoc test (F). Fisher’s exact test (G). *P < .05,**P < .01, and ***P < .001.