What are potential complications of untreated arrhythmias?

Untreated arrhythmias can lead to significant and potentially life-threatening complications, which is why this choice highlights the correct concerns. A stroke can occur due to the formation of blood clots as a result of irregular heart rhythms, especially in conditions like atrial fibrillation, where blood may pool in the heart chambers. Heart failure may develop because persistent arrhythmias can weaken the heart muscle over time, leading to its inability to pump effectively. Sudden cardiac arrest can result from severe arrhythmias, such as ventricular fibrillation, where the heart stops beating effectively, leading to loss of consciousness and death if not treated immediately.

In contrast, the other options do not accurately reflect the serious nature of untreated arrhythmias. Mild headaches are not typically recognized as a significant complication associated with arrhythmias. Improved heart efficiency and increased lung capacity are also not outcomes related to arrhythmias; rather, they would signify the opposite, healthy cardiac and respiratory function.