Which electrocardiogram change should prompt the nurse to question the use of ranolazine for the treatment of a client diagnosed with chronic angina?

QT prolongation on an electrocardiogram (ECG) is a significant change that warrants careful consideration when using ranolazine for treating chronic angina. Ranolazine is known to prolong the QT interval, and if a patient already exhibits QT prolongation on their ECG, the use of this medication could increase the risk of potentially life-threatening arrhythmias, such as torsades de pointes.

Monitoring the QT interval is crucial when any antianginal agent that impacts cardiac repolarization is considered. The presence of prolonged QT suggests that the heart’s electrical conduction system is being affected, which could lead to serious complications if not addressed prior to initiating treatment.

In contrast, other choices do not primarily indicate a risk that warrants questioning the use of ranolazine. An inverted P wave may indicate atrial abnormalities but does not specifically relate to the safety profile of ranolazine in terms of representing a contraindication. A short ST segment does not raise the same level of concern regarding arrhythmia risk. Normal sinus rhythm is a desirable finding and indicates a stable heart rhythm that would not prompt concerns over ranolazine therapy. Thus, QT prolongation is the key finding that would require further review before proceeding with the treatment.