Which of the following is NOT considered an extrinsic mechanism of arrhythmias?

Congenital heart defects are regarded as intrinsic factors rather than extrinsic mechanisms of arrhythmias. This is because such defects originate from structural or electrical abnormalities in the heart itself, which affect internal functioning and can lead to arrhythmias. In contrast, extrinsic mechanisms typically refer to external factors or influences that can disrupt the heart's normal rhythm, such as medications, substances, or environmental factors.

Heat exhaustion, digoxin, and lidocaine all represent external influences that can provoke arrhythmias through different pathways. Heat exhaustion can affect electrolyte balance and circulation, while digoxin and lidocaine are medications that can alter cardiac conduction and heart rate. These factors all stem from outside the heart's structural composition, emphasizing their extrinsic nature. Therefore, identifying congenital heart defects as an intrinsic issue helps differentiate the origins of arrhythmias effectively.