Idiopathic Ventricular Arrhythmias in the Absence of Structural Heart Disease are Associated with Concealed Structural Abnormalities as Detected by Speckle Tracking Strain Echocardiography

Abstract

Background: Idiopathic ventricular arrhythmias (IVA) are thought to occur in patients without overt heart disease. Mechanical dispersion (MD) and delta contraction duration (DCD), both reflecting myocardial heterogeneity and subclinical fibrosis, have been shown to predict ventricular arrhythmias. Hypothesis: We hypothesised that IVA patients may have abnormal MD and DCD indices indicating subclinical fibrosis. Methods: 2D strain analysis was performed (in sinus rhythm, exclusion of ectopic beats) in 23 consecutive patients with IVA (no structural heart disease by cardiac magnetic resonance imaging (MRI); Group A) prior to electrophysiological mapping/ablation, and compared to 23 age/gender matched healthy controls (Group B). Results: Baseline characteristics were similar for age and left ventricular [LV] ejection fraction (EF) (p = 0.1 for both) (Table 1). LV global longitudinal strain (GLS) was significantly lower (p = 0.03) and LV MD was significantly prolonged (p = 0.002) in the IVA group. DCD was also increased in patients compared to controls (p = 0.04). Despite an overlap, GLS < −18% and MD of >46 ms identified 14/23 (61%) of IVA patients. Using a MD >42 ms, there was a specificity of 87% and a sensitivity of 52% in identifying IVA patients from controls; MD >46 ms had 100% specificity but low sensitivity (35%).Table 1Age (years)LVEF (%)LV GLS (%)LV MD (ms)DCD (ms)IVA (Group A)44 ± 1661 ± 5−19.9 ± 3*p<0.05.44 ± 12*p<0.05.120 ± 47*p<0.05.Controls (Group B)40 ± 1364 ± 7−21.2 ± 233 ± 8.683 ± 29* p < 0.05. Open table in a new tab Conclusion: Despite demonstratable absence of electrical and structural abnormalities with state-of-the-art mapping and cardiac MRI, 2D strain can detect subtle changes in myocardial heterogeneity. This may indicate the presence of subclinical fibrosis and the need to follow these patients long-term. Further study is needed to examine if these changes are reversible with ablation.