How does the EKG appear in a patient taking quinidine?

How does the EKG appear in a patient taking quinidine?

• A. Narrowed QRS complex
• B. P wave becomes wide and notched, widened QRS complex, ST segment depression, QT prolongation
• C. Peaked T waves and shortened QT interval
• D. Inversion of T waves in all leads

Answer: (B)

Quinidine is a class IA antiarrhythmic medication commonly used to treat atrial fibrillation and other cardiac arrhythmias. When interpreting an EKG of a patient who is taking quinidine, it is important to recognize the characteristic changes induced by this drug.

The correct answer indicates that in a patient under quinidine treatment, the P wave may become wide and notched, reflecting the effect of the drug on atrial conduction. Additionally, quinidine is known to produce a widened QRS complex due to its action on sodium channels, which slows down conduction in the His-Purkinje system and ventricular myocardium. Moreover, patients taking quinidine often present with ST segment depression and QT interval prolongation, reflecting its influence on the cardiac action potentials and the prolonged repolarization phase.

This combination of EKG changes — wide and notched P waves, widened QRS complexes, ST segment depression, and QT prolongation — is a hallmark of quinidine therapy and is important for healthcare providers to identify, as it can help in monitoring the patient's response to treatment and in preventing potential complications like Torsades de Pointes, which can arise from excessive QT prolongation.