Abstract Body (Do not enter title and authors here): Introduction/Background:
Loeys-Dietz syndrome (LDS) is a rare autosomal dominant aortic aneurysm syndrome characterized by arterial tortuosity resulting in arterial aneurysms and dissections, with unique craniofacial and skeletal features including bifid uvula, cleft palate and hypertelorism. While the presence of atrial fibrillation (Afib) and arrhythmias have been reported in LDS patients, limited investigation has been completed regarding the associated risk and severity of vascular complications in relationship to these arrhythmias1,2.

Research Questions/Hypothesis:
Are there any differences in vascular outcomes in patients with LDS when experiencing various forms of tachyarrhythmia?

Goals/Aims:
To evaluate the relationship between various types of arrhythmias and vascular outcomes in patients with LDS, including arterial dissection, stroke, revascularization, and death.

Methods/Approach:
A large sample of LDS patients (n=436) from a single tertiary referral center was assessed for ICD-10 diagnoses of arrhythmia and outcomes of interest. Arrhythmias assessed included Afib, atrial flutter (AFL), premature ventricular contractions (PVCs), and supraventricular tachycardia (SVT). Outcomes were arterial dissection, hemorrhagic and ischemic stroke, revascularization, and all-cause mortality.

Results/Data:
Our cohort (n=436) had an average age of 47 and was 57.8% female. A total of 26 patients had a documented history of tachyarrhythmia: 16 (3.4%) Afib, 2 (0.5%) AFL, 6 (1.4%) SVT, and 2 (0.5%) PVC. LDS patients with Afib were at significantly higher risk of arterial dissection (25% vs 6.0%, OR: 5.3, p<0.01), revascularization (18.8% vs 3.3%, OR: 8.1, p<0.01), stroke (25% vs 3.6%, OR: 9.0, p<0.001), and death (25% vs 4.3%, OR: 7.4, p<0.01) compared to those without a documented history of arrhythmia. Other arrhythmia types evaluated were not significant. Predictors of any arrhythmia type included hypertension (78% vs 31%, OR: 1.5, p<0.001) and heart failure (39% vs 5.0%, OR: 2.3, p<0.001).

Conclusion:
Although rare, Afib in LDS patients is associated with adverse vascular outcomes and mortality compared to those without a history of arrhythmia. Furthermore, the magnitude of increased risk is striking. Early identification and management of Afib in LDS patients may be critical in mitigating the risk of potential vascular complications.