Prognostic Value of 2026 AHA/ACC Clinical Categorization in Acute Pulmonary Embolism Patients Presenting to the Emergency Department

Background: The 2026 American Heart Association/American College of Cardiology (AHA/ACC) Pulmonary Embolism Guideline (Creager et al., Circulation 2026) introduced a novel five-category (A-E) clinical classification system with subcategories and an R modifier, replacing prior risk stratification frameworks. Prospective validation of this classification system using composite clinical outcomes is lacking. Objective: To evaluate the prognostic value of the 2026 AHA/ACC clinical categorization (Categories A-E plus R modifier) for predicting 30-day Major Adverse Pulmonary Embolism Events (MAPEE) in emergency department (ED) patients with acute pulmonary embolism (PE). Methods: Prospective observational cohort study conducted at Marmara University Faculty of Medicine Emergency Department, enrolling 600 consecutive adult patients with confirmed acute PE by computed tomography (CT) pulmonary angiography between April 2026 and January 2027. Primary outcome: MAPEE composite (all-cause mortality OR hemodynamic deterioration OR treatment escalation OR cardiopulmonary resuscitation) within 30 days. Secondary outcomes include area under the receiver operating characteristic curve (AUC) comparison with the European Society of Cardiology (ESC) 2019 risk stratification (exploratory), negative predictive value (NPV) of low-risk categories (A+B) for safe discharge, MAPEE trend across C1/C2/C3, and R modifier odds ratio. Statistical analysis: Jamovi v2.x. Reporting follows the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) 2007 checklist.

Inclusion Criteria: 1. Age \>=18 years 2. Confirmed acute PE on CT pulmonary angiography (CTPA) within 24 hours of ED presentation 3. Informed consent obtained 4. Ability to complete 30-day follow-up Exclusion Criteria: 1. Chronic thromboembolic pulmonary hypertension (CTEPH) 2. Age \