Table 1 Differential effects of sex on the supraventricular electrophysiology and atrial arrhythmic susceptibility of unanesthetized rats

Parameter	Male (n = 13)	Female (n = 16)	P value
Animal weight (g)	386.5 ± 6.7	278.0 ± 5.3	<0.001***
RR interval (ms)	182.2 ± 4.21	168.6 ± 3.48	0.019*
PR interval (ms)	49.96 ± 1.15	46.99 ± 0.9	0.049*
CSNRT (ms)	20.29 ± 1.87	23.15 ± 1.69	0.267
AERP 70 CL (ms)	26.22 ± 1.45	31.56 ± 1.43	0.019*
AERP 100 CL (ms)	27.33 ± 1.48	31.10 ± 1.54	0.098
AERP 120 CL (ms)	26.11 ± 1.26	30.40 ± 1.59	0.053
AVERP 100 CL (ms)	75.08 ± 0.97	73.75 ± 1.67	0.534
AVERP 110 CL (ms)	73.31 ± 0.92	72.75 ± 1.78	0.797
AVERP 120 CL (ms)	73.38 ± 1.06	72.25 ± 1.73	0.602
AVERP 130 CL (ms)	71.92 ± 1.14	71.25 ± 1.57	0.742
AV 2:1 block (ms)	75.83 ± 1.72	70 ± 1.49	0.021*
AV Wenckebach block (ms)	90.83 ± 2.03	82.5 ± 1.34	0.004**
Regular SVT induction (%)	12.31 ± 2.69	10.63 ± 3.22	0.420
Regular SVT duration (s)	236.98 ± 140.37	125.55 ± 105.04	0.177
AF induction (%)	30.77 ± 6.72	9.69 ± 3.04	0.010*
AF duration (s)	48.57 ± 28.83	5.54 ± 1.89	0.016*
Mean CR	1.22 ± 0.03	1.1 ± 0.02	0.009**
Arrhythmic CR (%)	39.34 ± 5.83	16.81 ± 4.30	0.009**

Comparison between the supraventricular electrophysiological parameters of male and female rats obtained in the UAS 4 weeks after right-atrial quadripolar electrode implantation. Note the reduced AERP and markedly increased AF susceptibility in males compared with females. Mean CR refers to the average CR of the first 5 s post-induction bursts. The results of 20 induction bursts were averaged for each animal. Arrhythmic CR (%) refers to the percentage of post-burst windows with a CR greater than the arrhythmic threshold (1.236). For additional details, see the Methods. Values are given as the mean ± s.e.m. Statistical analysis: for the electrophysiological parameters, the Student’s t-test was applied; for arrhythmic parameters, the Mann–Whitney test was applied. *P < 0.05, **P < 0.01, ***P < 0.001.

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