Abstract Body: Heart failure (HF) is a major cause of death and disability worldwide, affecting over 64 million people across the globe. Its development is a complex sequelae subsequent to reduced ventricular function. To maintain adequate perfusion, the heart employs complex mechanisms to regulate contractile strength across a range of timescales, including regulation of ionic currents and growth (hypertrophy). The coordination of signaling events that direct these changes has profound effect on the systemic impact of this remodeling. While the mechanisms by which cardiac myocytes sense and respond to changes in demand are subject to intense study across the field, the mechanisms guiding spatial and temporal control of cardiac remodeling are unclear. Previous work has identified a role for the cytoskeletal protein β_IV-spectrin(β_IV) in membrane targeting and modulation of the two-pore mechanosensitive K+ channel TREK-1 with implications for both short-term changes in electrophysiology and longer-term remodeling. To test the hypothesis that β_IV drives cardiac remodeling in part by altering TREK-1 ion permeability, we measured intracellular Ca2+ and contractility using an IonOptix system in myocytes isolated from cardiac-specific β_IV knockout mice (β_IV cKO) as well as a double conditional knockout animal (β_IV^f/f x Kcnk2^f/f x αMHC-Cre (β_IV/TREK-1 cKO)). Interestingly, myocytes isolated from β_IV cKO hearts exhibit increased Ca2+ transient amplitude and peak sarcomere shortening compared to WT, which were normalized in the β_IV/TREK-1 cKO myocytes. These unanticipated findings support the hypothesis that β_IV regulates ion homeostasis in part by modulating TREK-1 activity with potential implications for cardiac remodeling in response to stress.