Drug of choice for ventricular tachycardia in a patient with myocardial ischemia is:
**Core Concept**
In the setting of ventricular tachycardia (VT) with myocardial ischemia, the primary goal is to restore a viable and stable cardiac rhythm while minimizing further myocardial damage. This requires the use of anti-arrhythmic agents that can effectively terminate VT while also addressing the underlying ischemic insult.
**Why the Correct Answer is Right**
The drug of choice in this scenario is **Lidocaine**. Lidocaine is a Class Ib anti-arrhythmic agent that works by blocking sodium channels in the cardiac membrane, thereby reducing automaticity and preventing the rapid depolarization of cardiac cells that drives VT. In the context of myocardial ischemia, lidocaine's ability to stabilize cardiac membranes and reduce the risk of re-entrant arrhythmias makes it an ideal choice for treating VT.
**Why Each Wrong Option is Incorrect**
**Option A:** **Procainamide** is a Class Ia anti-arrhythmic agent that can exacerbate myocardial ischemia due to its effects on potassium channels. This makes it a less desirable choice in this scenario.
**Option B:** **Amiodarone** is a Class III anti-arrhythmic agent that can be effective for treating VT, but it is not the first-line choice in the setting of myocardial ischemia due to its potential to worsen cardiac function and increase the risk of hypotension.
**Option C:** **Magnesium sulfate** is used to treat torsades de pointes and other forms of polymorphic VT, but it is not the primary choice for treating VT with myocardial ischemia.
**Clinical Pearl / High-Yield Fact**
In the setting of VT with myocardial ischemia, it's essential to remember that the goal of anti-arrhythmic therapy is to stabilize the cardiac membrane and prevent further myocardial damage. This means choosing an agent like lidocaine that can effectively terminate VT while also addressing the underlying ischemic insult.
**Correct Answer:** D. Lidocaine