A risk stratification model based on cardiac magnetic resonance (CMR) results demonstrated moderate prognostic performance in excessive trabeculation of the left ventricle (ETLV), driven primarily by adverse LV remodeling and fibrosis, according to research published Oct. 7 in JACC: Cardiovascular Imaging. Trabeculation metrics only modestly improved discrimination, with low-risk individuals demonstrating a favorable prognosis regardless of trabeculation extent.

In the retrospective, longitudinal study, investigators Guillem Casas, MD, et al., conducted a core-laboratory CMR analysis of 589 patients (mean age 43 years; 43% women; mean LVEF 48%) with ETLV across 17 centers in Europe and North America. Participants were eligible if they had a noncompacted-to-compacted (NC/C) ratio >2.3 and/or trabeculated myocardial mass percentage (TM%) >20%; 12% had late gadolinium enhancement (LGE). Patients were randomly assigned to derivation (n=412) or validation (n=177) cohorts.

Patients were stratified into risk tertiles using a prediction model derived from morphofunctional CMR parameters, including indexed LV end-diastolic volume, LV global longitudinal strain and LGE extent.

At a median follow-up of 3.6 years, 121 patients (21%) experienced the primary endpoint, a composite of major adverse cardiovascular events, including heart failure (11%), ventricular arrhythmia (9%), systemic embolism (3%) or all-cause death (2%) – an incidence rate of 5.83 events per 100 person-years. These patients more frequently exhibited LV dilatation and had lower LVEF and a higher prevalence of LGE.

The prediction model demonstrated moderate prognostic performance (C-statistic, 0.77 in derivation and 0.70 in validation) and improved discrimination beyond LVEF- and LGE-based risk stratification (ΔC-statistic, 0.04). Associations remained significant after adjustment for age and sex.

Adding TM% modestly improved discrimination (C-statistic, 0.79 in derivation, p=0.012; 0.72 in validation) while adding NC/C or maximal apical fractal dimension did not. An exploratory, hypothesis-generating cutoff of TM% ≥28% identified higher-risk patients (adjusted hazard ratio, 2.55; p<0.001), although the authors caution that this threshold requires external validation. This was driven by higher event rates in the intermediate- and high-risk tertiles; it was not predictive in the low-risk tertile among individuals with normal indexed LV end-diastolic volume, preserved LV global longitudinal strain and minimal LGE.

Casas and colleagues also analyzed a control cohort of 197 patients with dilated cardiomyopathy (mean age 55 years; 34% women; mean LVEF 35%; 41% with LGE). After propensity-score matching based on demographic and CMR parameters, prognosis was comparable between the two groups (6.34 vs. 6.98 events per 100 person-years; p=0.557).

"The comparable outcomes support the concept that prognosis in ETLV is primarily determined by the underlying morphofunctional phenotype rather than the trabeculation itself," write the authors. "This supports a phenotype-based interpretation of ETLV, in which trabeculation burden is clinically relevant mainly when accompanied by LV dilation, systolic dysfunction, abnormal deformation or myocardial fibrosis."