Final answer:
The nurse should hold the dose of metoprolol and contact the provider due to the client's second-degree heart block and bradycardia, as metoprolol could worsen the condition.
Step-by-step explanation:
If a client's telemetry pattern shows a second-degree heart block with a ventricular rate of 50, the nurse should hold the dose of metoprolol and contact the healthcare provider. Metoprolol is a β-blocker that can exacerbate bradycardia, potentially leading to cardiac complications. Given that β-blockers reduce heart rate and contractility by blocking β-1 receptors, administering metoprolol to a patient already demonstrating signs of heart block could worsen their condition. Therefore, the nurse should prioritize patient safety by reassessing the patient's cardiac status and seeking further medical guidance before proceeding with medication administration.