Abstract Body (Do not enter title and authors here): Background
Giant cell myocarditis (GCM) and cardiac sarcoidosis (CS) are rare inflammatory diseases of the myocardium with poor prognosis. Cardiovascular outcomes among both the disease have not been well studied with limited literature.

Objective
This study aims to investigate the cardiovascular outcomes among patients with GCM and CS.
Method
We queried the TriNeTX Global Collaborative Network for adult patients with Giant cell myocarditis and Cardiac sarcoidosis between January 2000 to May 2023 and created two groups: one with Giant cell myocarditis and second with Cardiac Sarcoidosis. Both the groups were followed for 6 months and 12 months. Propensity score matched analysis (PSM) was done for age, gender, race, BMI, hypertension, diabetes mellitus, chronic kidney disease, hemoglobin level, low-density lipoproteins level, left ventricular ejection fraction and various drugs including beta blockers, ACEi, ARBi, and statins. The primary outcome was all-cause mortality (ACM), while secondary outcomes were heart failure, heart transplant, ventricular tachycardia (VT), AV nodal block, and atrial flutter and fibrillations.

Result
After PSM, amongst the 4804 patients (2402 patients in each group), the mean age of patients was 57.1 and 57.6 years in GCM and CS groups respectively. PSM analysis showed that primary outcomes i.e., ACM was significantly higher in GCM both after 6 months (RR, 2.332 (95% CI: 1.645-3.305), P<0.001) and 1 year follow up (RR, 1.547 (95% CI: 1.209-1.981), P<0.001) as compared with CS group. However, secondary outcomes i.e., Heart failure at 6 month (RR 0.668, 95% CI: 0.523-0.854), P=0.001), and at 1 year (RR 0.604, 95% CI: 0.498-0.733), P<0.001), VT at 6 months (RR 0.342, 95% CI: 0.254-0.461), P<0.001), and at 1 year (RR 0.328, 95% CI: 0.257-0.419), P<0.001), AV nodal block at 6 month (RR 0.454, 95% CI: 0.336-0.613), P<0.001), and at 1 year (RR 0.437, 95% CI: 0.342-0.557), P<0.001), and atrial flutter and fibrillation at 6 months (RR 0.674, 95% CI: 0.484-0.942), P=0.020), and at 1 year (RR 0.592, 95% CI: 0.457-0.767), P<0.001) were found significantly lower in GCM group as compared with CS. On the other hand, heart transplant incidence was comparable between both the groups.
Conclusion
These findings suggest that giant cell myocarditis patients were having high risk of mortality and lower risk of heart failure, ventricular tachycardia, AV nodal block, and atrial flutter and fibrillation compared with cardiac sarcoidosis.