Feasibility and Effectiveness of a Ring-Type Blood Pressure Device (CART-BP) Compared With 24-Hour Ambulatory Blood Pressure Monitoring in HFrEF

Inclusion Criteria: 1. Age ≥ 19 years (male or female) 2. Diagnosed with heart failure and currently under treatment 3. Left ventricular ejection fraction (LVEF) ≤ 40% confirmed by echocardiography performed within 1 year prior to enrollment 4. Able to undergo both 24-hour ambulatory blood pressure monitoring and ring-type blood pressure measurement 5. Voluntarily provided written informed consent to participate in this clinical study Exclusion Criteria: 1. Office blood pressure: SBP \< 90 mmHg, or DBP \< 50 mmHg, or SBP \> 180 mmHg, or DBP \> 100 mmHg 2. Unable to perform 24-hour ambulatory blood pressure monitoring 3. Unable to wear or use the ring-type blood pressure device 4. Variability in three consecutive resting cuff blood pressure measurements ≥ 20 mmHg (SBP) or ≥ 10 mmHg (DBP) 5. Insufficient valid ABPM readings: \< 25 daytime or \< 12 nighttime measurements per ESH criteria; or \< 25 daytime or \< 12 nighttime valid readings from the ring-type device 6. Pregnant, suspected pregnancy, or breastfeeding 7. Judged by the investigator to be legally or mentally unfit to participate in the clinical study