7th February 2024

A 16-year-old male presents with syncopal episodes that come with exercise.

A 16-year-old male presents with syncopal episodes that come with exercise. She has an extensive family history of sudden cardiac death. An ECG shows a QTc interval of 550ms ( Normal of 360-460ms), with the remainder of the ECG appearing normal. Genetic testing has shown a mutation in the KCNQ1 gene as the underlying cause. 

Which phase of the cardiac conduction cycle does this condition affect?