Efficacy of Transcutaneous Auricular Vagus Nerve Stimulation on Alleviating Major Depressive Disorder in Patients With Acute Coronary Syndrome After Percutaneous Coronary Intervention:A Prospective, Double-Blind,Randomized Controlled Study

Inclusion Criteria: * Age ≥18 years * Meeting the diagnostic criteria for ACS * 14 days to 12 months after successful PCI, with stable vital signs * Meeting the diagnostic criteria for depression according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) * HAMD-17 score ≥7 and \<24 (mild-to-moderate depression), with HAMA score \<HAMD score; * Refusal of psychiatric consultation, antidepressant medication, or psychological therapy by the patient or their legal representative after full informed consent * Voluntary participation in the study and signing of the informed consent form Exclusion Criteria: * Severe heart failure (New York Heart Association \[NYHA\] class ≥III) * Uncontrolled hypertension (systolic blood pressure ≥180 mmHg and diastolic blood pressure ≥110 mmHg) * Electrocardiographic abnormalities (first-degree atrioventricular block with PR interval ≥0.20 s, second-degree type II or third-degree atrioventricular block at any time, 24-hour average heart rate ≤50 beats per minute, RR interval ≥3 s) or a history of syncope unrelated to the current ACS * Dialysis-dependent patients * Previous renal sympathetic denervation or vagal ganglion ablation * Expected survival time \<4 months * Pre-PCI diagnosis of severe mental illnesses, including schizophrenia, severe intellectual disability, or substance abuse * Current use of antipsychotic medications * High suicide risk * Pregnant or lactating women * Left ear diseases, acute exacerbation of asthma or chronic obstructive pulmonary disease, or other conditions precluding taVNS treatment * Implanted cardiac pacemaker, implantable cardioverter-defibrillator (ICD), or other implantable stimulators (e.g., vagus nerve stimulator, deep brain stimulator)