Diastolic function assessed from tagged MRI predicts heart failure and atrial fibrillation over an 8-year follow-up period: the multi-ethnic study of atherosclerosis

Abstract

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.

Trial registration: ClinicalTrials.gov NCT00005487.

Keywords: Atrial; Diastole; Fibrillation; Heart failure; Magnetic resonance imaging.

Figures

Figure 1

This figure illustrating the calculation of the proposed SRI from the circumferential strain and strain rate curves. More negative strain values indicate greater circumferential shortening. SRI is calculated as the ratio of the duration of very early relaxation to that of the diastolic interval, divided by the early diastolic strain rate peak. The myocardial relaxation as imagined with a hypothetical pressure curve and electrocardiograph for reference. SRI: strain relaxation index; RR int: RR interval; S peak: peak systolic strain rate; IVCT: isovolumic contraction time; IVRT: isovolumic relaxation time; E peak: peak early diastolic strain rate; A peak: peak atrial-diastolic strain rate; Tsys: time of occurrence of peak systolic strain; Tpos: time of occurrence of post-systolic strain peak.

Figure 2

This figure show the Kaplan–Meier survival curves for combined (A), HF (B), and AF (C), end-points across tertiles of log(SRI). Individuals were free of AF or HF at baseline. log(SRI) expressed as median (minimum, maximum) across three tertiles were Q1: 0.119 (−0.2.239, 0.544), Q2: 0.805(0.544, 1.034), and Q3: 1.378(1.034, 3.471). P < 0.001 for all trends.