RDW and RV-PA Coupling in Acute PE

Consecutive adults admitted via the emergency department or transferred to the participating center with confirmed acute PE will be screened by the study team.

• Demographic and clinical

• Age, sex, body mass index and Smoking status.
• Comorbidities: hypertension, diabetes mellitus, coronary artery disease, heart failure, Chronic Obstructive Pulmonary Disease, chronic kidney disease, prior venous thromboembolism, active cancer, recent surgery, recent immobilization, history of COVID -19 infection and vaccination.
• Current medications relevant to erythropoiesis or hemodynamics (ACE inhibitors/ARBs, beta-blockers, diuretics, iron supplementation, erythropoiesis-stimulating agents, anticoagulants on admission).
• Laboratory

• Complete blood count: hemoglobin, MCV, MCH, RDW-CV, RDW, white cell count and differential, platelet count, mean platelet volume.
• Renal and hepatic function: creatinine, eGFR, AST, ALT, total bilirubin.
• Cardiac biomarkers: high-sensitivity troponin. 3 Imaging
• CTPA: anatomic location of thrombus (main, lobar, segmental, subsegmental), presence of saddle embolus, RV/LV diameter ratio on axial imaging.

4.Echocardiography

All echocardiograms will follow a standardized acquisition protocol based on the American Society of Echocardiography and European Association of Cardiovascular Imaging recommendations for RV assessment. Key elements:

• Left lateral decubitus position when tolerated; semi-recumbent if dyspneic.
• ECG-gated digital loops of at least three consecutive cardiac cycles for each view.
• Mandatory views: parasternal long-axis and short-axis; apical four-chamber, RV-focused four-chamber, two-chamber, and three-chamber; subcostal four-chamber and IVC.
• M-mode through the lateral tricuspid annulus for TAPSE.
• Continuous-wave Doppler across the tricuspid valve for peak TR velocity (multiple windows attempted; agitated saline contrast may be used to improve TR signal at operator discretion).
• Tissue Doppler at the lateral tricuspid annulus for S'.
• Speckle-tracking acquisition optimized for RV strain (frame rate 50-80 fps). Studies will be acquired on a single ultrasound platform (or ≤2 platforms with documented inter-platform agreement) and analyzed offline using vendor-neutral software where possible. Studies failing image-quality criteria for the primary outcome will be flagged and the participant excluded from the primary analysis

Inclusion criteria

Age ≥ 18 years. Acute PE confirmed by computed tomography pulmonary angiogram (CTPA) performed within 24 h of presentation.

CBC obtained within 24 h of admission and before any blood transfusion. Transthoracic echocardiography feasible within 24 h of admission. Written informed consent.

Exclusion criteria

• Active hematologic malignancy or recent chemotherapy with myelosuppressive intent.
• Red blood cell transfusion within the preceding 90 days.
• Known hemoglobinopathy (e.g., sickle cell disease, thalassemia major).
• Chronic dialysis or eGFR < 15 mL/min/1.73 m².
• Pre-existing severe pulmonary hypertension (resting mean PAP ≥ 35 mmHg by prior right heart catheterization or echocardiographic PASP ≥ 60 mmHg before this admission), severe left-sided valvular disease, or known severe biventricular dysfunction.
• Hemodynamic instability requiring vasopressors at the time of echocardiography, as their hemodynamics may distort RV-PA coupling estimates.
• Inadequate echocardiographic image quality precluding measurement of TAPSE and a quantifiable TR jet for PASP estimation.
• Inability to provide informed consent.