Fig. 6

Figure 6. Abnormal sinoatrial node (SAN) function in adult Isl1^ΔISE/ΔISE mice.A, Average hourly heart rate in adult Isl1^ΔISE/ΔISE (red, n=3 for female and n=6 for male) and wild-type (WT) littermate mice (black, n=6 for female and n=5 for male). Error bars denote SEM. The low activity period is highlighted in gray (B) Heart rates were averaged over 1-minute intervals for each mouse studied in (A; n=11 WT and 9 Isl1^ΔISE/ΔISE, analyzed separately by sex), and then binned into 10 bpm bins for generation of heart rate histograms for WT and Isl1^ΔISE/ΔISE females (top) and males (bottom) Vertical scale bar=25 counts. Comparison was made between WT and Isl1^ΔISE/ΔISE for total counts <400 bpm (male) or 500 bpm (female) for each mouse. *P<0.05 for Mann-Whitney test. C, A 2-second ECG tracing from a WT mouse (top) and with 2 examples of sinus arrhythmias observed in 2 different Isl1ΔISE/ΔISE mice: a sinus pause (middle tracing), and an episode of bradycardia (bottom tracing). D, Quantification of numbers of sinus arrhythmias recorded per hour over a 24-hour period in n=11 WT and n=9 Isl1^ΔISE/ΔISE mice. E, Quantification of total percentage of time spent with heart rate <250 bpm (bradycardia) for 11 WT and 9 mutant mice. Comparison of WT and Isl1^ΔISE/ΔISE distribution were made with a Mann-Whitney test with the P value shown.