Fig. 1.

Critical observations related to mitochondrial dynamics and the etiology of HF. (A) Schematic diagram showing the spatial distribution of mitochondrial Ca²⁺ signaling components in heart. The ends of each intermyofibrillar mitochondrion are in close proximity (∼100 nm) to the Ca²⁺ release units (CRUs) that are located between the transverse-tubule (TT) and junctional SR (jsr) membranes [also see Williams et al. (24)]. (B) Venn diagram highlighting key differences and similarities in WT mice and mice with leaky RyRs (S2808D) and how these properties develop during HF. Observations related to the critical questions (outlined here) provoked by Santulli et al. (1) are bolded.