IL-1β and IL-6 effect on arrhythmia substrates. Panel A shows the effect of IL-1β (n=6) and IL-6 (n=5) on average Ca2+ alternans (Ca2+ ALT), APD50 and APD90 when administered to hCM alone. Levels of significance are compared to hCM where * p < 0.001 (for Ca2+ ALT, n=23), * p = 0.002 (for APD50, n=6), * p < 0.02 (for APD90, n=6). Panel B shows ELISA results for IL-1β (left) and IL-6 (right) in separate populations of bone marrow (BM) hMSCs, non-failing cardiac hMSCs, failing cardiac hMSCs, and hCM alone (n=4). Levels of significance are compared to BM hMSC where * p < 0.001 (for IL-1β), * p = 0.008 (for IL-6). Panel C shows the rescue of Ca2+ alternans induced by failing hMSCs (n=18) with anti-IL-6 (n=18) treatment. Levels of significance are compared to hCM (n=12) where * p < 0.001.