Abstract Body (Do not enter title and authors here): Background: Right atrial (RA) function contributes 15 - 30% to right ventricular stroke volume. However, limited studies have evaluated RA function in the setting of submassive pulmonary embolism (PE). We investigated whether the severity of right atrial dyssynchrony was associated with short-term mortality in patients with submassive PE.

Methods: We performed a retrospective cohort study of 251 patient with submassive PE. Strain analysis was applied retroactively using TomTec software. 201 patients had images sufficient for RA strain analysis. RA dyssynchrony was defined as absolute max opposing wall delay (maxOWD) which was the time interval between peak lateral and septal wall strain in RA (Figure1) The primary outcome was 30-day all-cause mortality. The severity of dyssynchrony was defined according to max OWD and divided into four groups; no delay, first tertile (mild), second tertile (moderate), and third tertiles (severe).

Results: The patient groups were defined as follows: no delay (0 ms; n = 40), first tertile/mild delay (> 0 ms, ≤ 4.49 ms; n = 52), second tertile/moderate delay (> 4.49 ms, ≤ 13.1 ms; n = 51), and third tertile/severe delay (> 13.1 ms; n = 52). Of 201 patients, 23 patients (11 %) died within 30 days after diagnosis. Kaplan-Meier curves showed significant difference among the four groups (p < 0.001). Additionally, there were significant differences between no delay and moderate delay groups (p = 0.0321) and between moderate and severe delay groups (p=0.010). (Figure2) Moreover, patients with severe RA dyssynchrony had 7.3 times higher risk of 30-day mortality compared to patients in other groups (p < 0.001).

Conclusions: The severity of RA dyssynchrony on presentation was associated with mortality in patients with submassive PE. Assessment of RA dyssynchrony on presentation could risk stratify patients with submassive PE.