Role of the Kallikrein-kinin System in Septic Cardiomyopathy

Inclusion Criteria: 1. Age \>= 18 years old. 2. Admitted to the Intensive Care Unit (ICU) with an anticipated length of stay exceeding 24 hours. 3. Patient or legally authorized representative provides written informed consent prior to enrollment. 4. Categorized into one of the following three mutually exclusive cohorts within 24 hours of ICU admission: * Cohort 1 (Non-sepsis Controls): Admitted for definitive non-infectious etiologies (e.g., severe trauma, major non-cardiac surgery) with no clinical or microbiological evidence of infection throughout the ICU stay. * Cohort 2 (Sepsis without SIC): Diagnosed with sepsis according to the Sepsis-3 criteria (acute change in SOFA score \>= 2 points driven by infection), but with normal cardiac troponin levels and preserved cardiac function. * Cohort 3 (Sepsis-Induced Cardiomyopathy, SIC): Diagnosed with sepsis according to the Sepsis-3 criteria, accompanied by new-onset myocardial injury (elevated cardiac troponin above the upper limit of normal) and/or echocardiographic evidence of myocardial dysfunction directly attributable to sepsis. Exclusion Criteria: 1. Pre-existing severe chronic cardiac conditions, including history of cardiac surgery, severe pre-existing heart failure (NYHA Class III or IV), persistent severe arrhythmias, or known primary cardiomyopathy (e.g., hypertrophic or dilated cardiomyopathy). 2. Acute non-infectious cardiovascular or cerebrovascular events prior to or upon ICU admission, such as acute myocardial infarction (Type 1), acute ischemic/hemorrhagic stroke, or cardiac arrest. 3. Severe end-stage comorbidities, including end-stage renal disease (ESRD) requiring chronic maintenance dialysis prior to this illness, Child-Pugh Class C hepatic cirrhosis, or advanced malignant tumors with a life expectancy \< 3 months. 4. History of paraquat poisoning or other toxic ingestions known to directly cause profound myocardial or pulmonary toxicity. 5. Pregnant or breastfeeding women. 6. Indeterminate or ambiguous infectious status (e.g., cases treated with empiric antibiotics for suspected infection but where infection could neither be confirmed nor ruled out), excluded to prevent misclassification bias. 7. Intellectual, psychological, or neurological disorders that preclude necessary clinical examinations or compliance with study procedures.