The goal of this clinical trial is to learn if preoperative intranasal dexmedetomidine works to reduce perioperative myocardial injury and myocardial infarction in patients undergoing elective percutaneous coronary intervention (PCI). It will also learn about the safety of intranasal dexmedetomidine. The main questions it aims to answer are:

Does preoperative intranasal dexmedetomidine lower the incidence of perioperative myocardial injury and myocardial infarction after PCI? Does intranasal dexmedetomidine cause safety concerns in patients undergoing PCI? Researchers will compare intranasal dexmedetomidine to a placebo (a look-alike substance that contains no drug) to see if intranasal dexmedetomidine works to protect the heart during PCI.

Participants will:

Receive either intranasal dexmedetomidine (100 μg) or a placebo (normal saline) 15 minutes before the PCI procedure Undergo blood tests to measure cardiac troponin levels before and after the procedure Be followed for up to 30 days after the procedure to record any heart-related events or side effects

Coronary heart disease (CHD) remains a major global health burden. Percutaneous coronary intervention (PCI) has become a cornerstone treatment for CHD, effectively reducing mortality. Despite its success, perioperative myocardial injury (PMI) is a frequent complication, occurring in 5-30% of patients, depending on the definition and sensitivity of cardiac biomarkers. PMI ranges from a mild, asymptomatic increase in high-sensitivity cardiac troponin (hs-cTn) to overt myocardial infarction. Even minor elevations in troponin are independently associated with increased 30-day and long-term major adverse cardiovascular events (MACE), as well as higher rates of stent thrombosis and restenosis. The pathophysiology of PMI is multifactorial, including distal embolization, side-branch occlusion, coronary dissection, and, importantly, an imbalance between myocardial oxygen supply and demand during the procedure.

Sedation is commonly used during PCI to relieve anxiety, pain, and stress; however, the choice of sedative and its impact on myocardial outcomes remain controversial. Dexmedetomidine, a highly selective α2-adrenoceptor agonist, provides sedation with minimal respiratory depression and has shown potential cardioprotective effects in preclinical and clinical studies, possibly through reducing sympathetic tone, decreasing myocardial oxygen consumption, and attenuating inflammatory and oxidative stress responses. Intranasal administration offers a non-invasive, convenient route with rapid absorption, making it an attractive option for premedication. Nevertheless, robust evidence from large-scale, multicenter randomized controlled trials is lacking.

This trail is designed to evaluate whether preoperative intranasal dexmedetomidine reduces the incidence of perioperative myocardial injury and myocardial infarction in patients undergoing elective PCI compared with placebo.

Inclusion Criteria:

• 18 years ≤ age ≤ 85 years;
• Patients scheduled to undergo elective coronary angiography or percutaneous coronary intervention (PCI);
• Classified as American Society of Anesthesiologists (ASA) physical status I-III (ranging from patients with mild systemic disease to those with more severe systemic disease that limits normal physical activity but who remain able to perform light daily tasks);
• Informed consent obtained.

Exclusion Criteria:

• Allergy or contraindication to dexmedetomidine, such as severe bradycardia (resting heart rate <50 beats/min), sick sinus syndrome, second-degree or higher atrioventricular block without a pacemaker;
• Severe cardiac dysfunction (left ventricular ejection fraction <35% or New York Heart Association functional class III-IV), cardiogenic shock, or hemodynamically unstable patients;
• Uncontrolled hypertension (systolic blood pressure >180 mmHg or diastolic blood pressure >110 mmHg) or hypotension (systolic blood pressure <90 mmHg);
• Sleep apnea-hypopnea syndrome or Body Mass Index >30 kg/m²;
• Use of alpha-2 adrenergic receptor agonists (e.g., clonidine) or antagonists, or tricyclic antidepressants, which may affect the action of the study drug, within 1 month before the procedure;
• Language, visual, or hearing impairment that may affect cognitive assessment;
• Hepatic or renal insufficiency (Alanine Aminotransferase/Aspartate Aminotransferase/Creatinine >3 times the upper limit of normal);
• Anatomical abnormalities of the nasal cavity affecting intranasal drug administration;
• Pregnant or breastfeeding women.