Risk stratification in nonischemic dilated cardiomyopathy: the role of T1/T2 mapping and extracellular volume

Background Risk stratification in nonischemic dilated cardiomyopathy (NIDCM) remains challenging. Cardiac magnetic resonance (CMR) not only aids in identifying underlying etiology but also offers a noninvasive means of myocardial tissue characterisation, which might be a valuable tool for prognostic assessment - through late gadolinium enhancement (LGE), parametric mapping, and extracellular volume (ECV). While recent studies have focused on the presence and extent of LGE, parametric mapping remains less explored but may provide complementary insights into diffuse interstitial fibrosis. Purpose To explore the predictive value of cardiovascular magnetic resonance (CMR) findings - T1, T2 mapping and ECV - for heart failure (HF) and arrhythmia-related events in NIDCM patients. Methods In this retrospective cohort study, patients diagnosed with NIDCM who underwent CMR at our center were included. All CMR images were acquired using a 1.5-T scanner. T1 mapping was quantified within the septal myocardium in areas without LGE enhancement (T1 native) and ECV was calculated using pre, post-contrast T1 and synthetic haematocrit. The primary outcomes were HF hospitalisation and arrhythmia-related events (defined as appropriate ICD therapy or sustained VT/VF or non-sustained VT). Results Among the 53 patients with NIDCM, 40% were women, with a median age of 64 years [IQR 52-69], the median LV ejection fraction was 40% [IQR 30-47] and 15% had an implantable device. During a median follow-up of 17 months [IQR 9-27], 6 patients (11%) had a HF hospitalisation and 11 patients (35%) had an arrhythmia-related event. ECV was similar across NYHA class (p=0.33), ECV was correlated with both NT-proBNP value (p=0.001), LV ejection fraction (p=0.001), as well as the presence of LGE (p=0.019, Figure 1). In univariable Cox regression analysis, although T1 mapping (HR=1.01, [95% CI, 0.99-1.02], p=0.3) and T2 mapping (HR=1.01, [95% CI, 0.83-1.23], p=>0.9) were not associated with higher risk of HF hospitalisation, patients with higher ECV had higher risk of HF hospitalisation (HR=1.11, [95% CI, 1.01-1.22], p=0.03, Table 1). Furthermore, neither CMR parameter was associated with increased risk of an arrhythmia-related event (Table 1). In multivariable Cox regression analysis, including age, gender and LV ejection fraction, ECV remain an independent predictor of HF hospitalisation (HR=1.13, [95% CI, 1.00-1.28], p=0.046, Table 1). Conclusions In this cohort of patients diagnosed with NIDCM, only extracellular volume was an independent predictor of HF hospitalisation. Arrhythmia-related risk was not associated with any of the CMR parameters.Uni- and Multivariable Cox regression Correlation between ECV and LGE presence