Under which circumstance is an ICD approved for primary prevention of sudden death?

An implantable cardioverter-defibrillator (ICD) is primarily approved for patients at high risk of sudden cardiac death due to life-threatening arrhythmias. In the case of patients with a confirmed diagnosis of long QT syndrome who experience syncope, there is a significant risk for potentially lethal tachyarrhythmias, such as torsades de pointes, which can lead to sudden cardiac arrest. Installing an ICD in these patients serves as a preventive measure against sudden death, demonstrating a clear clinical need based on their arrhythmic risk.

This specific indication distinguishes it from other circumstances that do not have the same level of justification for primary ICD placement. For example, patients with asymptomatic heart disease may not exhibit sufficient risk factors to warrant an ICD, as they are not currently presenting with critical arrhythmic events or syncope. Similarly, patients over the age of 75 with mild symptoms may not meet the rigorous requirements for primary prevention based solely on age or symptom severity. Lastly, patients with chronic arrhythmia but without syncope do not typically qualify for ICD placement since syncope indicates a higher risk scenario; hence, the intervention would be less justified in those without syncope.