Answer D (correct answer): Lidocaine is a class Ib antiarrhythmic that blocks cardiac sodium channels. Lidocaine preferentially binds ischemic cardiac tissue. In the setting of ischemia, the resting membrane potential in cardiac cells rises from the usual value of -85mEv to higher values closer to -60mEv. In this more depolarized state, lidocaine binds more readily and exerts more effect.
Answer A (incorrect answer): Lidocaine also binds more readily when sodium channels are in use and out of the resting state. Thus, it binds more at fast heart rates when sodium channels are more active. It binds less in the setting of bradycardia.
Answers B, C, and E (incorrect answers): Presence of depressed left ventricular ejection fraction, bypass tract, or pulmonary hypertension do not alter the binding of lidocaine to sodium channels.