INTRODUCTION: Type 2 diabetes (T2DM) is associated with cardiovascular death, including sudden cardiac death due to arrhythmias. Patients with an implantable cardioverter-defibrillator (ICD) are also at high risk of developing a clinically significant ventricular arrhythmia. It has been reported that sodium-glucose cotransporter 2 (SGLT2) inhibitors can reduce cardiovascular deaths; however, the physiological mechanisms of this remain unclear. It is, however, well known that SGLT2 inhibitors increase blood ketone bodies, which have been suggested to have sympatho-suppressive effects. Empagliflozin (EMPA) is an SGLT2 inhibitor. The current clinical trial titled "Placebo-controlled, double-blind study of empagliflozin (EMPA) and implantable cardioverter-defibrillator (EMPA-ICD) in patients with type 2 diabetes (T2DM)" was designed to investigate the antiarrhythmic effects of EMPA. METHODS: The EMPA-ICD study is a prospective, multicenter, placebo-controlled, double-blind, randomized, investigator-initiated clinical trial currently in progress. A total of 210 patients with T2DM (hemoglobin A1c 6.5-10.0%) will be randomized (1:1) to receive once-daily placebo or EMPA, 10 mg, for 24 weeks. The primary endpoint is the number of clinically significant ventricular arrhythmias for 24 weeks before and 24 weeks after study drug administration, as documented by the ICD. The secondary endpoints of the study are the change from baseline concentrations in blood ketone and catecholamine 24 weeks after drug treatment. CONCLUSION: The EMPA-ICD study is the first clinical trial to assess the effect of an SGLT2 inhibitor on clinically significant ventricular arrhythmias in patients with T2DM and an ICD. TRIAL REGISTRATION: Unique trial number, jRCTs031180120 ( https://jrct.niph.go.jp/latest-detail/jRCTs031180120 ).