The nurse understands that which of the following medications is a potassium channel blocker?

A. The TEE evaluates if emboli are present if cardioversion is required: A transesophageal echocardiogram (TEE) provides detailed imaging of the heart’s chambers, particularly the left atrium and left atrial appendage, where clots often form in atrial fibrillation. It is used to rule out thrombi before cardioversion to reduce the risk of stroke during the procedure.

B. The study will use electric current to stop the abnormal conduction pathway: This describes electrical cardioversion, not TEE. TEE is a diagnostic imaging procedure and does not involve the delivery of electrical currents to modify the heart's rhythm or conduction.

C. A TEE will help restore the client's underlying baseline normal rhythm: TEE does not treat arrhythmias. Its role is diagnostic—to visualize cardiac structures, not to restore normal rhythm. Cardioversion or pharmacologic agents are required to correct atrial fibrillation.

D. A TEE is required prior to implantable defibrillator placement in clients with atrial fibrillation: TEE is not routinely required before implantable cardioverter-defibrillator (ICD) placement. ICD decisions are usually based on ejection fraction, rhythm stability, and risk of sudden cardiac arrest, not the presence or absence of atrial thrombi.

A. Hypermagnesemia: Hypermagnesemia (high magnesium levels) can cause bradycardia, hypotension, and prolonged PR and QRS intervals. While it can affect cardiac rhythm, it's less commonly associated with PVCs. The client's magnesium level of 2.5 mg/dL is within the normal range (1.5-2.5 mg/dL).

B. Hypocalcemia: While the calcium level of 8.0 mg/dL is slightly low (normal: ~8.5–10.5 mg/dL), mild hypocalcemia is less commonly associated with PVCs compared to hypokalemia. It can affect cardiac contractility but is not the most likely cause of these arrhythmias.

C. Hypokalemia: The potassium level is 2.8 mEq/L, which is significantly below normal (normal: 3.5–5.0 mEq/L). Potassium is a crucial electrolyte for maintaining normal cardiac electrical activity. Hypokalemia increases myocardial excitability and can lead to various cardiac dysrhythmias and a known cause of ventricular irritability, including multifocal PVCs, and increases the risk of life-threatening arrhythmias in clients with cardiac or metabolic conditions.

D. Hyperglycemia: The glucose level of 200 mg/dL is elevated but not severely high. While it reflects poor glycemic control, it is not directly linked to the occurrence of PVCs. Electrolyte imbalances, particularly low potassium, are more arrhythmogenic.