The Nondilated Left Ventricular Cardiomyopathy Phenotype: Arrhythmic Prognosis and Differences With Dilated Cardiomyopathy

Nondilated left ventricular cardiomyopathy (NDLVC) has emerged as a new entity within the spectrum of nonischemic cardiomyopathies, characterized by impaired left ventricular (LV) systolic function in the absence of LV dilatation. This study aimed to compare baseline differences in characteristics between NDLVC and dilated cardiomyopathy (DCM), and to identify predictors of heart failure (HF) and sustained ventricular arrhythmias (VA) (VT/VF) hospitalization within the NDLVC subgroup. Patients with both DCM and NDLVC were eligible in this prospective observational cohort, with diagnostic classification being performed via cardiac magnetic resonance-derived volumes. Univariable and multivariable logistic regression models were used to identify differences in baseline characteristics and indices associated with HF and VA hospitalization. There were 122 patients in the study (NDLVC [n = 60], DCM [n = 62]). Compared to DCM, NDLVC patients had significantly smaller left-ventricular end-diastolic volume index (91 vs 103 ml/m², p = 0.015), shorter QRS duration (104 vs 115 ms, p = 0.02), and were more often in New York Heart Association class I (70% vs 45%, p = 0.004). In multivariable models, the NDLVC phenotype was independently associated with late potentials (odds ratio [OR] 2.82, 95% confidence intervals [CI] [1.25,6.69], p = 0.015), lower left-ventricular end-diastolic volume index (OR 0.97, 95% CI [0.95,0.99], p = 0.005), and shorter QTc (OR 0.98, 95% CI [0.96,0.99], p < 0.001). Among NDLVC patients and after a median follow-up of 41 months, 6/60 (10%) experienced HF, and 10/60 (17%) VA hospitalization. In multivariable models, HF hospitalization was associated with worse New York Heart Association class (OR 19.9, 95% CI [2.14,108.9] p = 0.006), reduced right ventricular ejection fraction (OR 0.81, 95% CI [0.60,0.95] p = 0.006), and lower indexed right-ventricular end-diastolic volume (OR 0.87, 95% CI [0.71,0.98] p = 0.014). VA hospitalization was independently associated with premature ventricular complexes >1,000/24 hours (OR=20.1, 95% CI [2.66,336], p = 0.002), right ventricular ejection fraction ≤45% (OR 0.85, 95% CI [0.71,0.96], p = 0.008) and prolonged QTc (OR 1.06, 95% CI [1.01,1.12], p = 0.005). In conclusion, NDLVC represents a distinct cardiomyopathy phenotype with preserved LV geometry and favorable functional status compared to DCM, yet a significant subset remains at-risk for adverse events, particularly VA. RV dysfunction and arrhythmic burden are key risk markers in NDLVC and warrant focused monitoring.