Transverse (T)-tubules are vital for the synchronous rise of systolic calcium. Heart failure (HF) results in atrial t-tubue loss and dyssynchronous calcium release. In the ventricle, recovery from HF is associated with t-tubule restoration and normalisation of systolic calcium. The mechanisms that control atrial t-tubules however, remain largely unknown, thus we aim to determine; i) if atrial t-tubule loss in HF can be recovered, ii) the effect of atrial t-tubule restoration on systolic calcium, iii) proteins involved in t-tubule recovery. Isoflurane anaesthetized (2-4% v/v in oxygen) sheep were instrumented with a pacemaker and pacing lead. Post-operative analgesia (meloxicam 0.5 mg/kg) and antibiosis (enrofloxacin 2.5 mg/kg) were provided for 48 hours. HF was induced by ventricular pacing at 210 bpm and, in a subset of animals pacing was terminated and the sheep allowed to recover for 5 weeks. Atrial myocytes were isolated and tissue samples taken from control, HF and recovered sheep following euthanasia with pentobarbitone (200 mg/kg iv; n=9 per group). T-tubule density was assessed using di-4-ANEPPS and intracellular calcium measured by confocal microscopy of Fluo-8AM loaded cells. To determine the involvement of specific proteins in t-tubule recovery, vectors encoding t-tubule proteins were transiently expressed in neonatal rat ventricular myocytes (NRVM). Data presented as mean ±S.E.M and statistical significance taken as p<0.05, determined using mixed model analysis. Atrial t-tubules were lost in HF (reduced by -81±5.6%, p<0.001) and the initial rise of systolic calcium was restricted to the surface sarcolemma. Cessation of tachypacing resulted in recovery of cardiac function and recovery of atrial tubule density to control values. The organization of recovered tubules was altered however, with recovered tubules being predominately longitudinally orientated, longer and more branched. Despite structural changes, the recovered tubules were functional; calcium was firstly released along the tubules, followed by propagation to the rest of the cell. Expression of t-tubule associated proteins BIN1, Tcap and MTM1 was decreased in heart failure (-24.8±8.6%, -49.4±9.6%; -24.5±7.9% respectively; p<0.05), with both Tcap and MTM1 fully restored to control levels following recovery from HF (p<0.01). BIN1 trended towards recovery with expression being no different to control. 48hrs transfection with BIN1 in NRVM led to the development of tubules, the structure of which was altered by coexpression with MTM1 and Tcap (n=7 litters). Atrial t-tubules are lost in a sheep model of HF; this is associated with dyssynchronous rise of systolic calcium. T-tubule proteins BIN1, MTM1 and Tcap also decrease during HF. Recovery of HF leads to upregulation of these proteins and restoration of atrial tubules, which are once again the main site for the rise of systolic calcium. Furthermore our data suggest Tcap and MTM1 play a role in shaping BIN1 induced tubule structures in NRVMs.