Study population
From May 2018 to July 2019, 281 patients with history of VAs were evaluated with both contrast-enhanced CMR imaging and 24-hour ambulatory Holter electrocardiogram (ECG) simultaneously within the timeframe of one month in our institution. Of the 281 patients, 15 were excluded because the interval between CMR and Holter ECG examinations was greater than one month, 176 were excluded due to the presence of structural heart diseases, defined by clinical histories and echocardiographic results (early coronary artery diseases, previous myocardial infarction, valvular heart diseases, and a family history of inheritable conditions, including channelopathies, hypertrophic cardiomyopathy, or arrhythmogenic right ventricular cardiomyopathy). Twelve were excluded based on severe LGE image artifacts that affected measurements (Figure 1 ). The final study population included 78 patients without structural heart disease. The study protocol was approved by the institutional review board at our institution, and all participants provided written informed consent.