Quantification of left atrial strain and strain rate using Cardiovascular Magnetic Resonance myocardial feature tracking: a feasibility study

Abstract

BackgroundCardiovascular Magnetic Resonance myocardial feature tracking (CMR-FT) is a quantitative technique tracking tissue voxel motion on standard steady-state free precession (SSFP) cine images to assess ventricular myocardial deformation. The importance of left atrial (LA) deformation assessment is increasingly recognized and can be assessed with echocardiographic speckle tracking. However atrial deformation quantification has never previously been demonstrated with CMR. We sought to determine the feasibility and reproducibility of CMR-FT for quantitative derivation of LA strain and strain rate (SR) myocardial mechanics.Methods10 healthy volunteers, 10 patients with hypertrophic cardiomyopathy (HCM) and 10 patients with heart failure and preserved ejection fraction (HFpEF) were studied at 1.5 Tesla. LA longitudinal strain and SR parameters were derived from SSFP cine images using dedicated CMR-FT software (2D CPA MR, TomTec, Germany). LA performance was analyzed using 4- and 2-chamber views including LA reservoir function (total strain [?s], peak positive SR [SRs]), LA conduit function (passive strain [?e], peak early negative SR [SRe]) and LA booster pump function (active strain [?a], late peak negative SR [SRa]).ResultsIn all subjects LA strain and SR parameters could be derived from SSFP images. There was impaired LA reservoir function in HCM and HFpEF (?s [%]: HCM 22.1?±?5.5, HFpEF 16.3?±?5.8, Controls 29.1?±?5.3, p?<?0.01; SRs [s?1]: HCM 0.9?±?0.2, HFpEF 0.8?±?0.3, Controls 1.1?±?0.2, p?<?0.05) and impaired LA conduit function as compared to healthy controls (?e [%]: HCM 10.4?±?3.9, HFpEF 11.9?±?4.0, Controls 21.3?±?5.1, p?<?0.001; SRe [s?1]: HCM ?0.5?±?0.2, HFpEF ?0.6?±?0.1, Controls ?1.0?±?0.3, p?<?0.01). LA booster pump function was increased in HCM while decreased in HFpEF (?a [%]: HCM 11.7?±?4.0, HFpEF 4.5?±?2.9, Controls 7.8?±?2.5, p?<?0.01; SRa [s?1]: HCM ?1.2?±?0.4, HFpEF ?0.5?±?0.2, Controls ?0.9?±?0.3, p?<?0.01). Observer variability was excellent for all strain and SR parameters on an intra- and inter-observer level as determined by Bland-Altman, coefficient of variation and intraclass correlation coefficient analyses.ConclusionsCMR-FT based atrial performance analysis reliably quantifies LA longitudinal strain and SR from standard SSFP cine images and discriminates between patients with impaired left ventricular relaxation and healthy controls. CMR-FT derived atrial deformation quantification seems a promising novel approach for the study of atrial performance and physiology in health and disease states.

Cardiovascular Magnetic Resonance Myocardial Feature Tracking

“…Both hypertrophic cardiomyopathy and heart failure with preserved EF patients show impaired LA reservoir and conduit function when compared with healthy controls. 22 In theory, similar assessments of right atrial physiology can be derived from the 4-chamber view, which is however more susceptible to breathing motion with associated higher variability. 43 …”

“…20,21 The study of atrial physiology using strain and SR imaging has recently been explored. 11,22 CMR-based deformation assessments of all cardiac chambers have become possible with FT, which could not reliably be achieved with myocardial tagging for the relatively thin-walled right ventricular (RV) and atrial myocardium.…”

“…Our group has identified different patterns of LA impairment associated with different diseases. 22 Patients with hypertrophic cardiomyopathy exhibit an increased contractile (booster pump) function, whereas patients with heart failure with preserved EF show impaired booster pump function compared with healthy controls. Both hypertrophic cardiomyopathy and heart failure with preserved EF patients show impaired LA reservoir and conduit function when compared with healthy controls.…”

“…11 Inoue et al 58 demonstrated the potential of CMR-FT-derived LA dynamics to improve risk stratification of cerebrovascular events in patients with atrial fibrillation. Because the assessment of CMR-FT-based atrial performance analysis has only recently been validated, 22,43 widespread prognostic information is currently lacking and future studies are awaited. Notwithstanding these considerations, the data from our group demonstrate reasonable agreement between STE and CMR-FT-derived ventricular GLS.…”

“…11,22 This methodology permits derivation of quantitative strain and SR parameters for each of the 3 functional components of atrial physiology: (1) the reservoir phase is characterized by collection of pulmonary venous return during ventricular systole, and reservoir function is indicated by global peak longitudinal total strain (ε s ) and global peakpositive SR (SRs). (2) Conduit phase describes the passage of blood to the LV during early ventricular diastole.…”