This project plans to design a randomized controlled clinical trial to evaluate the effect of dapagliflozin on ventricular arrhythmia in the participants with heart failure with reduced ejection fraction after ICD implantation by collecting and analyzing the data of ECG, cardiac ultrasound and ICD programming. This project will explore the anti-ventricular arrhythmia effect of dapagliflozin in HFrEF patients.

This is a single-center, randomized, controlled, double-blind study in Chinese heart failure participants with ICD implantation. This trial aims to investigate the effect of dapagliflozin on ventricular arrhythmias in participants with HFrEF. This trial includes a screening period, a treatment period and a follow-up period. Total duration of each subject's participation in the trial is approximately 1 year. During the screening period, 120 participants with HFrEF with ICD implanted in the investigator's department were recruited. The participants should sign the informed consent and be randomly divided into 2 groups. All participants will receive the best anti-heart failure treatment for 6 months before enrollment, including ACEI/ARB/ARNI, β-blockers, spironolactone, diuretics, and digitalis. One group was randomized to receive dapagliflozin (10 mg qd) and another group received place. Participants were then enrolled in a 1-year clinical trial and investigators will record the participants' QT interval, QTc interval, frequency and mode of ICD electrical therapy, cardiac function, symptoms, signs and other indicators before and after treatment to evaluate the occurrence of ventricular arrhythmia.

Inclusion Criteria:

patients received ICD therapy with HFrEF, including: ischemic cardiomyopathy, non-ischemic cardiomyopathy, LVEF ≤35% and optimized anti-HF therapy for at least 6 months.

Exclusion Criteria:

1. Type 1 diabetes or a history of repeated diabetic ketoacidosis.
2. Those who strictly restrict carbohydrate intake.
3. Genital infection.
4. Low blood pressure.
5. SGLT2i allergy.
6. Severe renal impairment or end-stage renal disease (eGFR<30ml/(min•1.73m^2)) or dialysis.
7. The water-electrolyte and acid-base balance disorders have not been corrected.
8. Bladder cancer.
9. Those taking other antiarrhythmic drugs except beta-blockers.
10. Other diseases cause the patient's life expectancy to be less than 1 year.