Lidocaine and amiodarone are used to increase which period of the accessory pathway?

The correct choice reflects that lidocaine and amiodarone are used to increase the refractory period of the accessory pathway in the heart. The refractory period is the time during which the myocardium cannot be re-excited after a contraction. By prolonging this period, these medications help prevent re-entrant tachycardias that can occur when there is an accessory conduction pathway, such as in cases of Wolff-Parkinson-White syndrome.

Lidocaine works primarily by blocking sodium channels, which stabilizes the cardiac cell membranes and decreases automaticity, thus prolonging the refractory period. Amiodarone, an antiarrhythmic drug, has multiple mechanisms of action, including potassium channel blocking effects that also contribute to increased refractory periods in various cardiac tissues.

Understanding how these drugs affect the refractory period is crucial in managing arrhythmias effectively, especially in critical care settings where arrhythmias can lead to significant hemodynamic instability.