A client with an automatic internal cardiac defibrillator (AICD) is taking amiodarone and starts on ciprofloxacin. Which condition increases their risk for life-threatening arrhythmia?

The selection of prolonged QT syndrome as the factor that increases the risk for life-threatening arrhythmia is accurate due to the pharmacological effects of both amiodarone and ciprofloxacin. Both of these medications have the potential to prolong the QT interval on the electrocardiogram (ECG).

Amiodarone is known to be a potent antiarrhythmic agent that can significantly lengthen the QT interval. This effect can lead to torsades de pointes, a specific type of life-threatening arrhythmia characterized by a rapid and irregular heartbeat. When ciprofloxacin is added to the treatment regimen, it can also contribute to QT prolongation. Hence, the combination of these two drugs in a client who already has an underlying condition of prolonged QT syndrome markedly heightens their risk for developing serious arrhythmias.

Other conditions listed, such as hypertension, diabetes, and bradycardia, while they may have their own risks or implications for cardiovascular health, do not directly correlate with the compounded risk of QT interval prolongation in the presence of these medications. Therefore, prolonged QT syndrome stands out as the critical condition that could notably escalate the risk of arrhythmic events in the client.