What is the best course of action for an elderly patient with hypertension and post-coronary bypass surgery, on metoprolol 50mg, ramipril, and aspirin, presenting with intermittent giddiness, sinus bradycardia, and blood pressure of 150/90 mmHg?

Immediate Management of Symptomatic Bradycardia in Post-CABG Patient

Stop metoprolol immediately and do not restart it until the bradycardia resolves, as beta-blockers are the most likely culprit causing symptomatic sinus bradycardia with a heart rate of 37 bpm in this patient. 1, 2

Critical First Steps

Discontinue the Offending Medication

• Metoprolol 50mg is causing symptomatic bradycardia and must be stopped immediately 1, 2
• Beta-blockers like metoprolol can precipitate severe bradycardia, especially in patients with underlying sinus node dysfunction, which is common in elderly post-cardiac surgery patients 2
• The FDA label explicitly warns that bradycardia, including sinus pause and heart block, can occur with metoprolol use, and recommends reducing or stopping the drug if severe bradycardia develops 2
• Patients presenting with symptomatic sinus node dysfunction secondary to reversible causes should first be managed by directing therapy at eliminating the offending condition 1

Assess for Immediate Danger

• With a pulse of 37 bpm and symptomatic giddiness, this patient requires urgent evaluation for hemodynamic instability 3
• Document whether the giddiness occurs specifically during bradycardic episodes to establish causality 1
• Check for signs of hypoperfusion: altered mental status, chest pain, dyspnea, or syncope 3

Acute Management Algorithm

If Hemodynamically Unstable

• Administer atropine 0.5-1 mg IV for immediate symptomatic relief 3
• Consider transcutaneous or transvenous pacing as a bridge if atropine is ineffective 3

If Hemodynamically Stable (Current Scenario)

• Observe for 24-48 hours after stopping metoprolol to allow drug washout 1
• Continue cardiac monitoring to document heart rate recovery 1
• Most patients will show improvement within days of stopping the offending beta-blocker 1

Address the Hypertension Separately

Blood Pressure Management Without Beta-Blockers

• Continue ramipril as it does not cause bradycardia and is appropriate for post-CABG patients 4, 5
• BP of 150/90 mmHg is not a hypertensive emergency and does not require immediate aggressive treatment 6
• Target BP approximately 10% above baseline rather than aggressive normalization 6
• Consider adding a diuretic (hydrochlorothiazide) or increasing ramipril dose once bradycardia resolves, as these do not affect heart rate 4, 5

Alternative Rate Control If Needed Later

• If rate control becomes necessary after bradycardia resolves (e.g., for atrial fibrillation), consider non-dihydropyridine calcium channel blockers (diltiazem, verapamil) at low doses with careful monitoring 1
• Avoid restarting metoprolol unless absolutely necessary and only after heart rate normalizes above 60 bpm 1, 2

Evaluation for Underlying Sinus Node Dysfunction

Clinical Assessment

• Post-CABG patients have increased risk of sinus node dysfunction due to surgical trauma to the sinus node or its blood supply 7
• The combination of elderly age, post-cardiac surgery status, and symptomatic bradycardia on a beta-blocker suggests possible underlying sinus node dysfunction unmasked by metoprolol 1, 8

Diagnostic Approach

• Ambulatory ECG monitoring (24-48 hour Holter) after stopping metoprolol to assess baseline sinus node function 1
• Document correlation between symptoms and heart rate 1
• Electrophysiology study is not indicated unless diagnosis remains uncertain after noninvasive evaluation 1

Pacemaker Consideration

When NOT to Pace

• Do not implant a permanent pacemaker while the patient is on metoprolol 1
• Asymptomatic or minimally symptomatic bradycardia after drug withdrawal does not require pacing 1
• If bradycardia resolves completely after stopping metoprolol, no pacemaker is needed 1

When to Consider Pacing

• Only if symptomatic bradycardia persists after eliminating reversible causes (stopping metoprolol and observing for adequate washout period) 1
• If persistent symptomatic sinus node dysfunction is documented off all negative chronotropic drugs 1
• Permanent pacing benefit in sinus node dysfunction is symptom relief and quality of life improvement, not mortality reduction 1

Common Pitfalls to Avoid

• Never implant a pacemaker without first stopping beta-blockers and observing for recovery - this is the most critical error to avoid 1
• Do not aggressively treat the BP of 150/90 mmHg with additional negative chronotropic agents while bradycardic 6
• Do not restart metoprolol at any dose until heart rate is consistently above 60 bpm and symptoms have resolved 2
• Avoid switching to other beta-blockers (they will cause the same problem) 2
• Do not perform electrophysiology studies in the acute setting while on beta-blockers 1

Follow-Up Plan

• Recheck heart rate and symptoms in 24-48 hours after stopping metoprolol 1
• If heart rate normalizes and symptoms resolve: continue ramipril, optimize BP control with non-bradycardic agents 4, 5
• If bradycardia persists beyond 5-7 days off metoprolol: proceed with ambulatory monitoring and consider permanent pacing evaluation 1
• Continue aspirin for post-CABG management 1