A 52-year-old man with hypertension and stable angina is started on atenolol 50 mg daily. After 2 weeks, he presents with severe bradycardia (HR 42/min), hypotension (BP 88/56 mmHg), and dizziness. He denies chest pain or dyspnea. ECG shows normal sinus rhythm with prolonged PR interval. What is the most appropriate immediate next step in management?

Explanation

## Clinical Scenario Analysis The patient has developed **severe symptomatic bradycardia (HR 42/min) and hypotension (BP 88/56 mmHg)** secondary to atenolol therapy. This constitutes a **hemodynamically significant adverse drug reaction** requiring immediate intervention — not dose titration. ## Why Discontinuation + Atropine is Correct **Key Point:** When a patient develops severe bradycardia (HR <50/min) AND hypotension (SBP <90 mmHg) on a beta-blocker, the offending drug must be **discontinued immediately**. Mere dose reduction is inappropriate when the patient is already hemodynamically compromised. **Clinical Pearl:** Atropine (0.5–1 mg IV, repeat up to 3 mg) is the **first-line pharmacological agent** for symptomatic bradycardia regardless of cause, including beta-blocker toxicity. It acts by blocking vagal tone at the SA node, increasing heart rate. For refractory cases, glucagon (1–5 mg IV) — which bypasses beta-receptors — is the antidote of choice for beta-blocker overdose (KD Tripathi 8e, Ch 12; Harrison's 21e). ### Rationale for Immediate Discontinuation + Atropine 1. **Hemodynamic instability is present**: HR 42/min + BP 88/56 mmHg = symptomatic bradycardia with hypotension. This is not a mild adverse effect amenable to dose reduction. 2. **Dose reduction (Option B) is inappropriate** in this acute setting — the patient is already in a compromised state; reducing from 50 mg to 25 mg will not provide rapid enough relief given atenolol's half-life of ~6–7 hours. 3. **Atropine** is the standard immediate treatment for symptomatic bradycardia per ACLS guidelines and is appropriate here as the first pharmacological step. 4. Concerns about **rebound angina** with abrupt discontinuation are secondary to the immediate threat of hemodynamic collapse; furthermore, the patient denies chest pain, and stabilization takes priority. ## Why Other Options Are Incorrect | Option | Why Wrong | |--------|----------| | Continue atenolol + add CCB | Catastrophically wrong — adding a negative chronotrope (diltiazem/verapamil) to an already bradycardic, hypotensive patient would worsen hemodynamic compromise. | | Reduce atenolol to 25 mg + monitor | Insufficient for acute hemodynamic instability; dose reduction takes hours to effect change given atenolol's pharmacokinetics. Not appropriate when BP is 88/56 mmHg. | | Exercise stress test | Absolutely contraindicated in acute symptomatic bradycardia and hypotension. | **High-Yield:** The management ladder for beta-blocker–induced bradycardia: (1) Discontinue drug → (2) IV Atropine → (3) IV Glucagon (antidote) → (4) Cardiac pacing if refractory. Dose reduction is only appropriate for **mild, asymptomatic** bradycardia without hemodynamic compromise. [cite: KD Tripathi 8e Ch 12; Harrison's Principles of Internal Medicine 21e; ACLS Guidelines 2020]