Observational Study to Describe Health-Related Quality of Life and Measure Disease Burden Among Patients With Long QT Syndrome Types (LQTS) 2 and 3

Inclusion Criteria: 1. The participant is willing and provides written informed consent to participate in this study. 2. Male or female participant of at least 18 years of age, English-speaking. 3. Confirmed genetic diagnosis of LQT2 or 3, demonstrated by one of the following: * Genetic testing report (pathogenic or likely pathogenic (P/LP) mutation) in KCHN2 or SCN5a genes) or, * A signed physician's letter confirming genetic diagnosis of LQTS 2 or 3. 4. Documented QTc ≥ 480 ms within the last year, demonstrated by one of the following: * 12-lead electrocardiogram (ECG), or * A signed physician's letter confirming an ECG demonstrating QTc value ≥ 480 ms. 5. The participant is able to operate a smartphone and a companion watch. \*The number of participants with QTc between 480 and 500 ms will be limited to 50. Exclusion Criteria: 1. Current participation in another clinical trial involving a drug or device. 2. Participants unwilling to use an iPhone or Apple Watch for the duration of the study. 3. Known diagnosis of Brugada Syndrome 4. Participants unwilling to comply with outlined procedures.