OBJECTIVE: In healthy volunteers, a positive association has previously been observed between emotional awareness (EA), the ability to identify and describe emotional experiences in oneself and others, and resting heart rate variability (HRV), which is dominated by vagus nerve activity. The current study aimed to investigate the EA-HRV association across multiple assessments in a "real-world" ambulatory context in patients with long QT syndrome (LQTS) who are at genetic risk for sudden cardiac death. METHODS: Participants (157 LQTS patients; Mean Age = 35.1, SD Age = 10.4; 115 women) completed the levels of emotional awareness scale (LEAS) on one occasion, which served as our measure of EA. In an ecological momentary assessment study involving 10 assessments per day over 3 days, multiple 5-minute ECG assessments (mean = 24.6, SD = 5.1) were obtained in each patient using a Holter monitor, from which high-frequency HRV (HF-HRV) was computed on each occasion. RESULTS: There was a significant positive association between LEAS scores and HF-HRV controlling for biobehavioral covariates. We also detected a similar inverse relation between EA and mean heart rate. CONCLUSION: These findings suggest that, in patients with a well-defined genetic risk for ventricular arrhythmia and sudden death, the ability to experience emotions in a complex and differentiated way covaries with greater parasympathetic influences on the heart. These findings are consistent with the overlapping neural substrates of EA and HRV and their common contribution to adaptive emotional responding, consistent with the Neurovisceral Integration Model.