What to do for a patient on atenolol with sinus bradycardia and syncope?

Management of Syncope with Sinus Bradycardia in a Patient on Atenolol

Discontinue atenolol immediately, as beta-blockers can cause symptomatic bradycardia and syncope, and are contraindicated when bradycardia is the likely cause of syncope. 1, 2

Immediate Actions

Stop atenolol now - the combination of syncope and documented sinus bradycardia (58 bpm) in a patient on atenolol represents a clear drug-related adverse effect requiring immediate discontinuation. 1, 2

• Beta-blockers like atenolol are well-documented to cause symptomatic bradycardia, heart block, and syncope, particularly in patients with underlying conduction system abnormalities. 3, 2
• The FDA label explicitly warns that "bradycardia and heart block may occur as an unwanted effect of beta blockers" and states "if bradycardia or hypotension requiring treatment or any other untoward effects occur, atenolol should be discontinued." 2
• Multiple case reports document syncope and severe bradycardia specifically with atenolol, with resolution after drug discontinuation. 4, 5, 6

Monitoring After Discontinuation

Monitor the patient closely for 48-72 hours after stopping atenolol:

• Obtain serial ECGs to assess heart rate recovery and look for conduction abnormalities (PR interval, QRS duration, evidence of heart block). 1
• Check vital signs frequently, particularly heart rate and blood pressure. 1
• Consider ambulatory monitoring (Holter or event recorder) to evaluate for pauses, additional arrhythmias, or persistent bradycardia. 1, 7
• The heart rate should normalize within days as atenolol is eliminated (half-life 6-7 hours in normal renal function). 2

Evaluation for Underlying Causes

Assess for reversible causes of bradycardia beyond the medication:

• Evaluate renal function, as atenolol is renally excreted and accumulation can worsen bradycardia in renal impairment. 2
• Check electrolytes (particularly potassium), thyroid function (hypothyroidism), and review all other medications for bradycardia-promoting agents. 3
• Consider whether this represents neurally-mediated syncope (vasovagal) with a cardioinhibitory component that was unmasked or worsened by the beta-blocker. 3

Risk Assessment for Pacing

Determine if permanent pacing is needed based on symptom-rhythm correlation:

• If bradycardia and syncope resolve completely after stopping atenolol, pacing is not indicated - this was drug-induced. 3
• If symptomatic bradycardia persists despite medication withdrawal, permanent pacing is indicated for symptomatic sinus node dysfunction. 3
• The European Society of Cardiology guidelines state that "cardiac pacing is indicated and has proved highly effective in patients with sinus node dysfunction when bradyarrhythmia has been demonstrated to account for syncope." 3
• Dual-chamber (DDD) pacing is preferred over single-chamber ventricular pacing if permanent pacing becomes necessary. 3

Management of Hypertension Going Forward

Do not restart beta-blocker therapy if bradycardia was the cause:

• Beta-blockers are contraindicated in patients with symptomatic bradycardia. 3
• Alternative antihypertensive agents should be selected: ACE inhibitors, ARBs, calcium channel blockers (dihydropyridine type like amlodipine, NOT verapamil or diltiazem which also cause bradycardia), or thiazide diuretics. 3
• If rate control is needed for another indication (e.g., atrial fibrillation), consider non-dihydropyridine calcium channel blockers cautiously or digoxin, but only after bradycardia has fully resolved. 3

Critical Pitfalls to Avoid

Common errors in this scenario:

• Do not restart atenolol or any beta-blocker until you have definitively ruled out intrinsic sinus node disease and the patient has been stable off the medication for an extended period. 1
• Do not attribute the syncope to vasovagal causes without first eliminating the beta-blocker - the guidelines explicitly state that "beta-blockers may enhance bradycardia in the carotid sinus syndrome and in all other cardioinhibitory forms of neurally-mediated syncope." 3
• Do not use beta-blockers to treat vasovagal syncope - five long-term controlled studies have shown they are ineffective, and they may worsen cardioinhibitory responses. 3
• Avoid combining bradycardia-promoting drugs - if the patient requires multiple cardiac medications, be aware that combinations of beta-blockers with other agents (amiodarone, digoxin, non-dihydropyridine calcium channel blockers) dramatically increase bradycardia risk. 3, 2

Acute Treatment if Severe Bradycardia Persists

If the patient remains severely symptomatic with heart rate <40 bpm or hemodynamic compromise:

• Administer atropine 0.5-1 mg IV, repeatable every 3-5 minutes up to 3 mg total. 2
• If atropine is ineffective, consider isoproterenol infusion or temporary transvenous pacing. 2
• Hemodialysis can remove atenolol in cases of severe overdose or renal failure. 2

The key principle: syncope with documented bradycardia in a patient on a beta-blocker is a drug effect until proven otherwise, and the medication must be stopped immediately. 1, 2