Synopsis

Restrictive cardiomyopathy (RCM) is a rare form of heart muscle disease that is characterized by restrictive ventricular filling. The overall prognosis of RCM is poor with progression to heart failure and mortality. The primary aim of this study is to evaluate the association between myocardial strain and major RCM adverse events, such as death. The secondary aim is to assess the difference of MRI variables in RCM between women and men. The results demonstrated that decreased left-atrial longitudinal strain is significantly associated with mortality in RCM, independent of other MRI and clinical measures and beyond the need for gadolinium administration.

INTRODUCTION

Restrictive cardiomyopathy (RCM) represents a spectrum of disorders with a common physiology, but divergent etiologies, half of which may not be identified [1,2]. RCM is a rare form of heart muscle disease that is characterized by restrictive filling of the ventricles. In this disease, systolic function is usually normal, but the relaxation of the heart during diastole is very abnormal. The overall prognosis of RCM is poor with progression to heart failure and increased mortality, especially with positive findings in late gadolinium enhancement imaging.

However, in the era of unknown long-term effects of the gadolinium, attempts have been made to find other imaging biomarkers associated with RCM without the need for gadolinium injection. In this respect, myocardial strain showed to be an early marker of the development of several cardiovascular diseases [3]. Specifically, the recently developed MRI Feature Tracking technique showed potential for evaluating heart mechanics with results comparable to those obtained by standard MRI tagging, besides the advantages of not increasing scan time or requiring complicated post-processing [3].

The primary aim of this study is to evaluate the association between MRI-derived ventricular and left-atrial strain and major adverse cardiac events, such as death, in RCM. The secondary aim is to assess the difference of MRI imaging variables in RCM between women and men.

METHODS

Ninety eight patients with RCM (30 women and 68 men); age 61 ± 13 years referred to MRI from 2007 to 2015 were included in the study. All patients were followed to date to evaluate major adverse cardiac event and deceased status. The MRI exam consisted of: 1) cine images (horizontal, vertical, and left ventricular outflow tract long-axes and a stack of parallel short-axis slices covering the heart); and 2) late gadolinium enhancement (LGE) images. The cine imaging parameters were as follows: steady state with free precession (SSFP) pulse sequence, TR = 3.1 ms, TE = 1.55 ms, flip angle = 50⁰, Matrix = 256x256, slice thickness = 8mm, and bandwidth = 1127 Hz/pixel. The LGE imaging parameters were as follows: Inversion recovery (IR) sequence, TR = 6 ms, TE = 3 ms, flip angle = 25⁰, Matrix = 256x256, slice thickness = 8 mm, and bandwidth = 249 Hz/pixel. TI was adjusted based on a Look-Locker sequence to null signal from normal myocardium.

The images were post-processed using Medis software. The cine images were used for measuring indexed left ventricular (LV) mass, ventricular volume, ejection fraction (EF), and ventricular and left-atrial (LA) strain (Figures 1). The LGE images were used for assessing myocardial scar.

Univariate and multivariate logistic regression analysis with stepwise elimination of variables adjusted for cardiovascular disease risk factors were performed to identify MRI variables associated with mortality (p < .05 was considered significant).

RESULTS

Fifty patients (51%) had multiple myeloma and 39 (40%) had amyloidosis. 46 (47%) patients demonstrated signal enhancement on the LGE images and 35 (36%) experienced death. While mortality in patients with RCM was significantly associated with lower body mass index (p = .03) and higher indexed LV mass (p = .05), only LA longitudinal strain (p = .001) (Figure 2), older age (p = .05), and presence of amyloid and diabetes (p = .02 and .05) remained significantly associated after adjustment in the regression analysis (Table 1). The presence of LGE was not associated with mortality (p = .29).

Women with RCM demonstrated higher LV circumferential strain peak (mean ± SD = 7.4 ± 1.7 versus 6.5 ± 1.6, p = .03), smaller indexed ventricular end-diastolic volumes (p = .005 and .01 for LV and RV, respectively), and smaller LA volume (p = .05). Mortality in women was not significantly different than in men (p = .36).

DISCUSSION and CONCLUSION

MRI Feature Tracking is a valuable technique for evaluating cardiac strain in RCM patients beyond the need for gadolinium administration. Compared to different MRI strain imaging techniques, e.g. MRI tagging [4], SENC [5], and DENSE [6], MRI Feature Tracking is a valuable technique for measuring global atrial strain without the need for additional scan time or complicated post-processing, which makes it an ideal candidate for measuring strain in thin structures like the atria.

In conclusion, decreased LA longitudinal strain is significantly associated with mortality in patients with RCM, independent of other MRI and clinical measures.

Acknowledgements

References

1. Modesto et al, Prog Cardiovasc Dis; 57:111-124

2. Cecchi et al, Global Cardiol Sci Pract; 4:1-11

3. Ibrahim, Heart Mechanics. MRI; CRC Press; 2017.

4. Axel et al, Radiology; 171:841-845

5. Osman et al, Magn Reson Med; 46:324-334

6. Aletras et al, Magn Reson; 140:41-57