Chamber-specific long-term prognosis of intracardiac thrombus: a 21-year propensity-matched cohort study

Background The prognostic impact of intracardiac thrombus varies by cardiac chamber, yet large-scale comparative long-term outcome data across all four chambers remain limited. Methods In this retrospective propensity-matched cohort study using the Chang Gung Research Database (2001–2022), we identified 1,541 patients in the final propensity-matched analytic cohorts with echocardiographically confirmed single-chamber intracardiac thrombus [left atrial (LA) n = 619, left ventricular (LV) n = 774, right atrial (RA) n = 125, right ventricular (RV) n = 23]. Patients were 1:4 matched with controls without thrombus for demographics, comorbidities, and medications. Primary outcomes included ischemic stroke/systemic embolism, pulmonary embolism, myocardial infarction, heart failure, cardiac death, and major adverse cardiovascular events (MACE; composite of the above). Follow-up continued until the first event, death, or December 31, 2022. Findings Compared with matched controls, LA thrombus was associated with increased risks of ischemic stroke/systemic embolism (hazard ratio, HR = 1.85), heart failure (HR = 1.30), cardiac death (HR = 2.02), and MACE (HR = 1.61). LV thrombus was associated with increased risks of ischemic stroke/systemic embolism (HR = 1.38), myocardial infarction (HR = 1.58), heart failure (HR = 1.40), cardiac death (HR = 1.32), and MACE (HR = 1.36). RA thrombus was associated with pulmonary embolism (HR = 4.63), heart failure (HR = 1.70), and MACE (HR = 1.63), whereas cardiac death was not significantly increased (HR = 1.96). RV thrombus was rare and showed no significant associations with any outcome. Left atrial appendage thrombus did not confer additional risk compared with non-appendage LA thrombus. Conclusions The prognostic impact of intracardiac thrombus is strongly location-dependent. LV and LA thrombi carried the broadest cardiovascular risks, RA thrombus was disproportionately linked to pulmonary embolism and mortality, and RV thrombus had limited long-term impact. These findings support chamber-specific risk stratification and management strategies for patients with echocardiography-detected intracardiac thrombus.