Aerobic Interval Training Prevents Age-Dependent Vulnerability to Atrial Fibrillation in Rodents

Figures

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  Figure 1. Exercise capacity and cardiac chamber size measured after the 16 week intervention period. (A) Maximal oxygen uptake. (B) Echocardioraphic measurements of: Upper: Left atrial diameter. Lower: Left ventricular internal diameter in diastole. LAD, Left atrial diameter; LVIDd, Left ventricular internal diameter in diastole; Old-ex, Older exercised animals; Old-sed, Older sedentary animals; Young-sed, Younger sedentary animals; VO2max, Maximal oxygen uptake. *p < 0.05; **p < 0.01; ***p < 0.001; vs. old-sed.

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  Figure 2. AF vulnerability after the 16-week intervention period. AF vulnerability measured by in vivo electrophysiology after the 16-week intervention period. (A) Surface ECG (top) and intra-atrial ECG (bottom) recordings from in vivo electrophysiology in; Upper: Young-sed with SR. Middle: Old-sed with sustained AF. Lower: Old-ex with non-sustained AF. (B) Left: Inducibility of AF by in vivo electrophysiology. Right: Number of AF induced episodes per animal. (C) Left: Duration of the longest AF episode in each animal. Right: Duration of all recorded AF episodes for all animals, showing intra-group variation. Number refers to different animals in each group. AF, Atrial fibrillation; ECG, electrocardiogram; NSAF, Non-sustained AF; SAF, Sustained AF; SR, Sinus rhythm. *p < 0.05 vs. old-sed. Error bars are only shown one-sided where crossing 0.

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  Figure 3. Ex vivo electrophysiology after the 16-week intervention period. (A) CV probe on isolated perfused heart, and example recording from CV measurements. (B) Right atrial CV (young-sed n = 5, old-sed n = 7, old-ex n = 6). (C) AP rise time (10-90%) measured in RA at a cycle length of 175 ms (young-sed n = 5, old-sed n = 7, old-ex n = 6). (D) APD at 90% repolarization at a cycle length of 175 ms for right atrium (young-sed n = 5, old-sed n = 7, old-ex n = 6). (E) Example AP recordings of old-ex and old-sed animals. (F) AP amplitude alternans (left) and APD alternans magnitude (right) at a stimulation cycle length of 60 ms in the right atrium. APD, Action potential duration; CL, Cycle length; CV, Conduction velocity. *p < 0.05 vs. old-sed.

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  Figure 4. Atrial fibrosis. (A) Examples of Massons' Trichrome staining from the right atrium in: Left: Young-sed. Middle: Old-sed. Right: Old-ex animals. The endocardial and perivascular fibrosis seen in the images were excluded from analyses. Insets at higher magnification for better visualization of fibrosis. Arrows denote fibrotic areas. (B) Amount of interstitial fibrosis in the right (young-sed n = 11, old-sed n = 8, old-ex n = 11) and left atrium (young-sed n = 10, old-sed n = 9, old-ex n = 9). **p < 0.01 vs. old-sed.

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  Figure 5. Connexin 43 at immunohistochemistry. (A) Photomicrographs of cx-43 stained samples at immunohistochemistry. Upper: Young-sed. Middle: Old-sed. Lower: Old-ex. Arrows denotes lateralization of cx-43. (B) Upper: Total cx-43 at the cell surface. Lower: Proportion of cx-43 at the lateral cell margin. Cx-43 = Connexin 43; old-ex (n = 9); old-sed (n = 9); young-sed (n = 11). **p < 0.01. ***p < 0.001 vs. old-sed.