Reduced regional and global functions of the left atrium are related to both regional replacement and diffuse myocardial fibrosis processes. PurposeTo investigate the association between left atrial (LAleft atrium) function and left ventricular myocardial fibrosis using cardiac magnetic resonance (MR) imaging in a multi-ethnic population.Materials and MethodsFor this HIPAA-compliant study, the institutional review board at each participating center approved the study protocol, and all participants provided informed consent. Of 2839 participants who had undergone cardiac MR in 2010–2012, 143 participants with myocardial scar determined with late gadolinium enhancement and 286 age-, sex-, and ethnicity-matched control participants were identified. LAleft atrium volume, strain, and strain rate were analyzed by using multimodality tissue tracking from cine MR imaging. T1 mapping was applied to assess diffuse myocardial fibrosis. The association between LAleft atrium parameters and myocardial fibrosis was evaluated with the Student t test and multivariable regression analysis.ResultsThe scar group had significantly higher minimum LAleft atrium volu...

Objectives The strain relaxation index (SRI), a novel diastolic functional parameter derived from tagged magnetic resonance imaging (MRI), is used to assess myocardial deformation during left ventricular relaxation. We investigated whether diastolic function indexed by SRI predicts heart failure (HF) and atrial fibrillation (AF) over an 8-year follow-up. Methods As a part of the multi-ethnic study of atherosclerosis, 1544 participants free of known cardiovascular disease (CVD) underwent tagged MRI in 2000–02. Harmonic phase analysis was used to compute circumferential strain. Standard parameters, early diastolic strain rate (EDSR) and the peak torsion recoil rate were calculated. An SRI was calculated as difference between post-systolic and systolic times of the strain peaks, divided by the EDSR peak. It was normalized by the total interval of relaxation. Over an 8-year follow-up period, we defined AF ( n = 57) or HF ( n = 36) as combined ( n = 80) end-points. Cox regression assessed the ability of SRI to predict events adjusted for risk factors and markers of subclinical disease. Integrated discrimination index (IDI) and net reclassification index (NRI) of SRI, compared with conventional indices, were also assessed. Results The hazard ratio for SRI remained significant for the combined HF and AF end-points as well as for HF alone after adjustment. For the combined end-point, IDI was 1.5% ( P < 0.05) and NRI was 11.4% ( P < 0.05) for SRI. Finally, SRI was more robust than all other existing cardiovascular magnetic resonance diastolic functional parameters. Conclusion SRI predicts HF and AF over an 8-year follow-up period in a large population free of known CVD, independent of established risk factors and markers of subclinical CVD.