Prolonged Electromechanical Interval Unmasks Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy in the Subclinical Stage

INTRODUCTION: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is characterized by high incidence of ventricular arrhythmias. Overt ARVD/C is preceded by a subclinical stage with lack of detectable ECG and structural abnormalities. Activation delay is present before structural abnormalities and is a hallmark of arrhythmogenesis. Deformation imaging may unmask activation delay in the subclinical stage.

METHODS: Three groups were compared: (1) mutation-positive definite ARVD/C-patients fulfilling 2010 Task Force criteria (TFC) (n = 44); (2) asymptomatic mutation carriers not fulfilling TFC and without history of ventricular arrhythmias (n = 31); and (3) controls (n = 30). All underwent ECG and echocardiographic deformation imaging. As a surrogate for local activation delay the electromechanical interval (EMI) was measured, defined as time between onset-QRS and onset of shortening. Arrhythmic outcome (PVC-count, VT) of asymptomatic mutation carriers was correlated with EMI and ECG TFC.

RESULTS: In definite ARVD/C-patients, EMI was prolonged in all lateral RV segments. In asymptomatic mutation carriers, prolonged EMI was detected in the subtricuspid area in 14/31. Terminal activation duration ≥55 milliseconds (definition: supporting information) was the only ECG abnormality in this group (8/31). After a mean follow-up of 4.2 ± 3.1 years 10/31 asymptomatic mutation carriers experienced arrhythmic outcome. Prolonged subtricuspid EMI was the only parameter significantly associated with arrhythmogenesis during follow-up.

CONCLUSION: In ARVD/C-patients, EMI prolongation was present throughout the RV. In asymptomatic mutation carriers, prolonged EMI in the subtricuspid area is often detected without any additional abnormalities. These preliminary results indicate that prolonged EMI is a new parameter unmasking activation delay in the subclinical stage and may contribute to risk stratification.