Background In sudden cardiac arrest survivors without an immediately identifiable cause, additional extensive yet individualised testing is required. Methods We describe 3 survivors of sudden cardiac arrest in whom exercise stress testing was not performed during the initial hospital admission. Results All 3 patients were incorrectly diagnosed with long QT syndrome based on temporary sudden cardiac arrest–related heart rate–corrected QT interval prolongation, and exercise stress testing was not performed during the initial work-up. When they were subjected to exercise stress testing during follow-up, a delayed diagnosis of catecholaminergic polymorphic ventricular tachycardia (CPVT) was made. As a result, these patients were initially managed inappropriately, and their family members were initially not screened for CPVT. Conclusion In sudden cardiac arrest survivors without an immediately identifiable cause, omission of exercise stress testing or erroneous interpretation of the results can lead to a delayed or missed diagnosis of CPVT, which may have considerable implications for survivors and their family.