Abstract 13147: Non-invasive Identification of Carditis in Acute Rheumatic Fever and Rheumatic Heart Disease

Abstract

Background: The pathogenesis of acute rheumatic fever (ARF) and its evolution into rheumatic heart disease (RHD) is poorly understood. We aimed to identify carditis in patients with ARF and RHD using cardiac magnetic resonance (CMR) tissue characterisation with T1 mapping. We hypothesised that prolonged native T1 time on CMR, would be present in ARF and RHD patients. Methods: We prospectively recruited 62 patients. We recruited 16 patients fulfilling the Jones Criteria for the diagnosis of ARF, 15 controls with an inflammatory condition and 10 healthy controls. We also recruited 11 patients with echocardiographic evidence of RHD and 10 matched controls. All patients underwent CMR with assessment of non-contrast myocardial T1 mapping. The myocardial T1 time, as an index of myocardial inflammation from carditis, was compared between the groups. All T1 times were converted to Z-scores, to enable comparison with different CMR systems. Findings: Patients with ARF had evidence of carditis demonstrated by markedly elevated mean myocardial T1 times. The mean Z score was 2.76(95% CI 1.34-4.17) for patients with ARF compared to 0.32(95% CI -0.25-0.88) for those with non-cardiac inflammatory conditions and 0.00(95% CI -0.72-0.72) for healthy controls, P=0.004. A myocardial T1 Z score greater than 1.4 showed excellent diagnostic performance as a single test for the diagnosis of ARF (AUC = 0.85[0.67-0.99], P=0.001, sensitivity = 82 %, specificity = 92%, Youden’s J = 0.74). Patients with RHD also demonstrated significantly elevated native T1 time compared to matched controls. The mean Z score for RHD patients was 2.79(95% CI 1.3-4.3) compared to 0.00(95% CI -0.72-0.72) in controls, P=0.002. Interpretation: Patients with ARF and RHD have markedly elevated myocardial T1 Z-scores on CMR, consistent with carditis. Incorporating CMR T1 mapping into the diagnostic algorithm for ARF may improve diagnostic certainty and lead to more effective delivery of secondary penicillin prophylaxis.