Regional and temporal progression of atrial remodeling in angiotensin II mediated atrial fibrillation

FIGURE 1. Time course of the effects of Ang II on systolic blood pressure. Systolic pressure was measured at baseline, 3 days, 10 days and 21 days of Ang II infusion. *p < 0.05 vs baseline; + p < 0.05 vs Ang II (3 days) by one-way repeated measures ANOVA with a Holm-Sidak posthoc test; n=5 mice per group.

FIGURE 2. Susceptibility to atrial fibrillation after Ang II infusion. (A) Representative surface (top) and intracardiac (bottom) ECGs illustrating the induction of AF after burst pacing in the right atrium in a mouse infused with Ang II. The recordings on the right are magnified regions of the recordings on the left showing the ECGs during AF and the spontaneous reversion back to sinus rhythm (SR). (B) Inducibility of AF in mice infused with saline for 21 days or Ang II for 3, 10 and 21 days. Numbers in parentheses indicate the number of mice induced into AF. *p < 0.05 vs saline; + p < 0.05 vs Ang II (3 days) by Fisher’s exact test. (C) Duration of AF in the mice that were induced into AF as shown in panel B.

FIGURE 3. Time course of the effects of Ang II on atrial electrophysiology (A) Representative ECGs in mice infused with saline for 21 days or Ang II for 3, 10 and 21 days. (B) Overlay of ECGs showing a single beat in saline infused mice and mice infused with Ang II for 3, 10 and 21 days. Colors are as shown in panel (A) (C) Summary of P wave duration in mice infused with saline or Ang II for 3, 10 and 21 days. (D) Summary of AERP in mice infused with saline or Ang II for 3, 10 and 21 days. For panels (C and D) *p < 0.05 vs saline, + p < 0.05 vs Ang II (3 days), ^ p < 0.05 vs Ang II (10 days) by one-way ANOVA with a Holm-Sidak posthoc test; n=19 mice for saline, 15 for Ang II (3 days), 15 for Ang II (10 days) and 13 for Ang II (21 days).

FIGURE 4. Time course of the effects of Ang II on right and left atrial AP morphology. (A) Representative APs in isolated right atrial myocytes from mice infused with saline for 21 days or Ang II for 10 and 21 days. (B) Representative APs in isolated left atrial myocytes from mice infused with saline for 21 days or Ang II for 3, 10 and 21 days. (C–J) Summary of cell capacitance (C), resting membrane potential (RMP, (D), AP upstroke velocity (Vmax, (E), AP overshoot (F), AP duration at 20% repolarization (APD20, (G), APD50 (H), APD70 (I) and APD90 (J) in right and left atrial myocytes from mice infused with saline or Ang II for the specified durations. *p < 0.05 vs saline, + p < 0.05 vs Ang II (3 days), ^ p < 0.05 vs Ang II (10 days) by one-way ANOVA with a Holm-Sidak posthoc test. For right atrial myocytes, n=14 for saline, 19 for Ang II (10 days) and 31 for Ang II (21 days). For left atrial myocytes, n=10 for saline, 15 for Ang II (3 days), 16 for Ang II (10 days) and 13 for Ang II (21 days).

FIGURE 5. Comparison of action potential morphology in left and right atrial myocytes after 21 days of Ang II infusion. (A–H) Summary of cell capacitance (A), RMP (B), Vmax (C), overshoot (D), APD20 (E), APD50 (F), APD70 (G), and APD90 (H) in mouse right (RA) and left (LA) atrial myocytes at 21 days of Ang II. *p < 0.05 vs RA by Student’s t-test; n=31 myocytes for RA and 13 myocytes for LA.

FIGURE 6. Time course of the effects of Ang II on left atrial sodium current. (A) Representative INa recordings in left atrial myocytes from mice infused with saline for 21 days or Ang II for 3, 10 and 21 days. INa voltage clamp protocol shown below recordings. (B) INa IV curves for left atrial myocytes isolated from mice infused with saline or Ang II for 3, 10, and 21 days. (C) INa steady-state activation curves for left atrial myocytes isolated from mice infused with saline or Ang II for 3, 10 and 21 days. (D) Summary of INa V1/2(act) for left atrial myocytes isolated from mice infused with saline or Ang II for 3, 10 and 21 days. (E) Summary in INa slope factor (k) for left atrial myocytes isolated from mice infused with saline or Ang II for 3, 10 and 21 days. For panels (B and C) *p < 0.05 vs saline, + p < 0.05 vs Ang II (3 days) at indicated membrane potentials by two-way repeated measures ANOVA with a Holm-Sidak posthoc test. For panels (D and E) *p < 0.05 vs saline by one-way ANOVA with a Holm-Sidak posthoc test; n=12 myocytes for saline, 17 for Ang II (3 days), 9 for Ang II (10 days) and 13 for Ang II (21 days).

FIGURE 7. Time course of the effects of Ang II on total right and left atrial potassium currents. (A) Representative total IK recordings in right and left atrial myocytes isolated from mice infused with saline for 21 days or Ang II for 3, 10 and 21 days. Voltage clamp protocol shown beside recordings. (B) Summary IK IV curves measured at the peak of the IK recordings for right atrial myocytes isolated from mice infused with saline or Ang II for 10 and 21 days. *p < 0.05 vs saline, + p < 0.05 vs Ang II (10 days) by two-way repeated measures ANOVA with a Holm-Sidak posthoc test. (C) Summary IK IV curves measured at the peak of the IK recordings for left atrial myocytes isolated from mice infused with saline or Ang II for 3, 10 and 21 days. *p < 0.05 vs saline at indicated membrane potentials by two-way repeated measures ANOVA with a Holm-Sidak posthoc test. For right atrial myocytes n=12 for saline, 14 for Ang II (10 days) and 21 for Ang II (21 days). For left atrial myocytes n=11 for saline, 15 for Ang II (3 days), 17 for Ang II (10 days) and 12 for Ang II (21 days).

FIGURE 8. Time course of the effects of Ang II on right and left atrial potassium currents after an inactivating pre-pulse. (A) Representative IK recordings following a pre-pulse to inactivate Ito in right and left atrial myocytes isolated from mice infused with saline for 21 days or Ang II for 3, 10 and 21 days. Voltage clamp protocol shown beside recordings. (B) Summary IK IV curves, measured at the peak of the IK recordings following a pre-pulse, for right atrial myocytes isolated from mice infused with saline or Ang II for 10 and 21 days. (C) Summary IK IV curves, measured at the peak of the IK recordings following a pre-pulse for left atrial myocytes isolated from mice infused with saline or Ang II for 3, 10 and 21 days. *p < 0.05 vs saline at indicated membrane potentials by two-way repeated measures ANOVA with a Holm-Sidak posthoc test. For right atrial myocytes n=12 for saline, 14 for Ang II (10 days) and 21 for Ang II (21 daysay). For left atrial myocytes n=11 for saline, 15 for Ang II (3 days), 17 for Ang II (10 days) and 12 for Ang II (21 days).

FIGURE 9. Time course of the effects of Ang II on the transient outward potassium current in right and left atrial myocytes. (A) Representative recordings showing the difference currents from IK recordings with and without a pre-pulse (shown in Figure 6, Figure 7) in right and left atrial myocytes isolated from mice infused with saline for 21 days or Ang II for 3, 10, and 21 days. These difference currents represent Ito in each condition. (B) Ito IV curves in right atrial myocytes isolated from mice infused with saline or Ang II for 10 and 21 days. (C) Ito IV curves in left atrial myocytes isolated from mice infused with saline or Ang II for 3, 10 and 21 days. *p < 0.05 vs saline at indicated membrane potentials by two-way repeated measures ANOVA with a Holm-Sidak posthoc test. For right atrial myocytes n=12 for saline, 14 for Ang II (10 days) and 21 for Ang II (21 days). For left atrial myocytes n=11 for saline, 15 for Ang II (3 days), 17 for Ang II (10 days) and 12 for Ang II (21 days). (D) Comparison of Ito density at +50 mV in right atrial (RA) and left atrial (LA) myocytes after 21 days of Ang II infusion. *p < 0.05 vs RA by Student’s t-test; n=21 myocytes for RA and 12 myocytes for LA.

FIGURE 10. Time course of the effects of Ang II on right and left atrial fibrosis. (A) Representative images demonstrating interstitial fibrosis (collagen fibres stained red) in the right and left atria in mice infused with saline for 21 days or Ang II for 3, 10 and 21 days of Ang II. (B–C) Summary of interstitial fibrosis in the right (B) and left (C) atria of mice infused with saline or Ang II for 3, 10 and 21 days. *p < 0.05 vs saline, + p < 0.05 vs Ang II (3 days), ^ p < 0.05 vs Ang II (10 days) by one-way ANOVA with a Holm-Sidak posthoc test. For right atrium n=8 saline, 8 Ang II (3 days), 6 Ang II (10 days) and 5 Ang II (21 days). For left atrium n=8 for saline, 9 for Ang II (3 days), 6 for Ang II (10 days), 6 for Ang II (21 days). (D) Comparison of fibrosis in the right (RA) and left (LA) atria of mice after 21 days of Ang II infusion. *p < 0.05 vs RA by Student’s t-test; n=5 for RA and 6 for LA.

FIGURE 11. Expression of angiotensin II type 1 receptor in the right and left atria of mice. Comparison of mRNA expression of AT1R in the right and left atria of untreated wildtype mice. Data analyzed by Student’s t-test; n=7 for right atrial and 7 for left atrial groups.