CMR-Verified Diffuse Myocardial Fibrosis Is Associated With Diastolic Dysfunction in HFpEF
What is the relationship between diffuse myocardial fibrosis and left ventricular (LV) systolic and diastolic dysfunction?
Cardiac magnetic resonance (CMR) was performed in 40 patients with systolic heart failure (SHF), 62 patients with heart failure with preserved ejection fraction (HFpEF), and 22 patients without heart failure (non-HF) in this study. CMR included cine imaging and measurement of diffuse myocardial fibrosis by calculation of extracellular volume fraction (ECV) using T1 mapping. The relationships between ECV and LV function were evaluated.
Groups were similar in age, although there were significant differences in gender, hypertension, coronary artery disease, and myocardial infarction (p < 0.05 for each). In comparison to the median (interquartile range) ECV in non-HF patients (27.9% [26.2-29.4%]), the ECV in those with HFpEF was higher (28.9% [27.8-31.3%], p = 0.006), and patients with SHF had higher ECV (31.2% [29.0-34.1%]) than both the non-HF (p < 0.001) and HFpEF cohorts (p < 0.05). Median (interquartile range) peak filling rate (a CMR measurement of diastolic function) was highest in non-HF patients (3.86 s-1 [3.34-4.48]), and was significantly lower in both individuals with HFpEF (2.89 s-1 [2.13-3.50], p < 0.001) and SHF (1.00 s-1 [0.79-1.49], p < 0.001). In patients with HFpEF, there were significant correlations between ECV and LVEF (r = -0.54, p < 0.01), and ECV and peak filling rate (r = -0.39, p < 0.01); no significant correlations were observed between these pairs of variables in non-HF patients or those with SHF.
Patients with SHF and HFpEF have increased diffuse myocardial fibrosis as compared to non-HF patients. There is a significant correlation between myocardial fibrosis and diastolic dysfunction in those with HFpEF.
While several studies have implicated diffuse myocardial fibrosis in diastolic dysfunction, this remains difficult to study in vivo. CMR techniques, such as measurement of ECV by T1 mapping, provide a promising means to determine the severity of diffuse myocardial fibrosis in a noninvasive manner. This study demonstrates that patients with HFpEF have increased diffuse myocardial fibrosis as compared to non-HF patients, although there was a significant overlap in observed interquartile ranges, which may make discrimination between groups challenging. The correlation between diffuse myocardial fibrosis and diastolic dysfunction by CMR supports a relationship between increased diffuse myocardial fibrosis and more severe diastolic dysfunction. However, the correlation was only moderate (r = -0.39), suggesting that these CMR measurements do not provide the entire picture.
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