What is the appropriate evaluation and management for a patient presenting with sinus bradycardia, chest pain, and shortness of breath?

Sinus Bradycardia with Chest Pain and Dyspnea

In a patient presenting with sinus bradycardia accompanied by chest pain and dyspnea, immediate evaluation for acute coronary syndrome is mandatory, followed by rapid identification and treatment of reversible causes before any pharmacologic or device intervention. 1

Immediate Assessment Priorities

This presentation represents symptomatic bradycardia requiring urgent intervention because chest pain (suggesting myocardial ischemia) and dyspnea (indicating inadequate cardiac output or heart failure) are cardinal symptoms that mandate treatment. 2 Asymptomatic bradycardia—even with rates as low as 37-40 bpm—requires no therapy, but the presence of chest pain or dyspnea changes management completely. 2

Critical Initial Steps

• Obtain a 12-lead ECG immediately to document the rhythm, rate, PR interval, QRS duration, and identify any ischemic changes (ST-segment elevation/depression, T-wave inversions) that would indicate acute myocardial infarction. 2
• Assess hemodynamic stability by checking blood pressure (systolic <90 mmHg indicates instability), mental status (confusion or decreased responsiveness), and signs of shock (cool extremities, delayed capillary refill, end-organ hypoperfusion). 2
• Measure cardiac biomarkers (troponin) urgently because acute myocardial infarction—especially inferior MI—is a common reversible cause of symptomatic bradycardia. 1, 2

Identification of Reversible Causes (Class I Priority)

Before administering any chronotropic drugs or considering pacing, systematically evaluate and treat reversible etiologies. 1, 2 This is the highest-priority recommendation in all major guidelines.

Medication Review (Most Common Reversible Cause)

• Review and discontinue or reduce beta-blockers, non-dihydropyridine calcium channel blockers (diltiazem, verapamil), digoxin, amiodarone, sotalol, or ivabradine. 1, 2
• If the offending medication is essential for guideline-directed therapy (e.g., beta-blocker post-MI), permanent pacing may be necessary to continue the drug. 2

Acute Myocardial Ischemia/Infarction

• Inferior wall MI is a classic cause of sinus bradycardia due to ischemia of the sinoatrial node (supplied by the right coronary artery in 60% of patients). 1, 2
• Treat the underlying ischemia with reperfusion therapy (PCI or thrombolytics); bradycardia often resolves once perfusion is restored. 1, 2
• Aminophylline 250 mg IV bolus may be considered specifically for high-grade AV block associated with inferior MI. 1

Other Reversible Causes to Evaluate

Cause	Evaluation	Treatment
Hypothyroidism	TSH, free T4	Levothyroxine replacement [1,2]
Electrolyte abnormalities	Serum K⁺, Mg²⁺	Correct hypo-/hyperkalemia, hypomagnesemia [1,2]
Obstructive sleep apnea	Clinical suspicion, sleep study	CPAP therapy [1,2]
Elevated intracranial pressure	Neuroimaging	Neurosurgical consultation [1,2]
Drug overdose (beta-blocker, CCB)	History of ingestion	Glucagon 3-10 mg IV bolus, then 3-5 mg/h infusion [1,2]

Acute Pharmacologic Management

First-Line: Atropine

Atropine 0.5-1 mg IV bolus is the first-line agent for symptomatic bradycardia, repeated every 3-5 minutes up to a maximum total dose of 3 mg. 1, 2 This is a Class I/IIa recommendation.

Critical dosing considerations:

• Never give doses <0.5 mg because paradoxical worsening of bradycardia can occur due to central vagal stimulation at low doses. 1, 2
• Absolute contraindication: Do not give atropine to heart transplant recipients without autonomic reinnervation, as it may precipitate high-grade AV block. 1, 2

Atropine is most effective for:

• Sinus bradycardia (as in this case) 1
• AV nodal blocks 1
• Less effective for infranodal blocks (which present with wide-complex escape rhythms) 2

Second-Line: Catecholamine Infusions

If atropine fails and the patient has LOW risk for coronary ischemia, consider catecholamine infusions (Class IIb). 1, 2 However, in this patient with chest pain suggesting ischemia, catecholamines should be avoided because they increase myocardial oxygen demand. 1

If catecholamines are necessary despite ischemia risk:

• Dopamine 5-20 µg/kg/min IV (preferred for combined chronotropic and inotropic support) 1, 2
• Epinephrine 2-10 µg/min IV or 0.1-0.5 µg/kg/min IV 1, 2
• Isoproterenol 1-20 µg/min IV (pure β-agonist; avoid in coronary ischemia because it decreases coronary perfusion while increasing oxygen demand) 1, 2

Temporary Pacing (Bridge Therapy)

Transcutaneous pacing is reasonable for severe symptoms or hemodynamic compromise unresponsive to atropine, serving as a bridge to transvenous or permanent pacing (Class IIa). 2 This is particularly important if the patient develops hypotension, altered mental status, or worsening chest pain despite atropine.

Transvenous pacing is indicated for persistent hemodynamic instability refractory to medical therapy, though it carries a 14-40% complication rate (venous thrombosis, pulmonary emboli, arrhythmias, perforation). 2

Definitive Management: Permanent Pacemaker

Permanent pacing is indicated (Class I) if symptomatic bradycardia persists after reversible causes have been excluded or adequately treated. 1, 2 In this patient, if the chest pain and dyspnea are directly attributable to bradycardia and persist despite treating ischemia, medications, and other reversible factors, permanent pacing is necessary.

Additional Class I indications:

• High-grade AV block (Mobitz II or third-degree) with symptoms 2
• Bradycardia caused by essential guideline-directed therapy with no alternative 2

Common Pitfalls to Avoid

• Do not delay treatment while awaiting laboratory results in a hemodynamically unstable patient; atropine or temporary pacing takes precedence. 2
• Do not use catecholamines (especially isoproterenol) in patients with active chest pain because they worsen myocardial ischemia. 1, 2
• Do not implant a permanent pacemaker before fully evaluating and correcting reversible causes such as acute MI, medications, or electrolyte abnormalities. 2
• Do not give atropine doses <0.5 mg (may paradoxically worsen bradycardia). 1, 2

Clinical Algorithm Summary

1. Immediate ECG + troponin to identify acute MI 1, 2
2. Assess hemodynamic stability (BP, mental status, signs of shock) 2
3. Treat reversible causes (especially acute MI, medications, electrolytes) 1, 2
4. If symptomatic despite treatment:
   • Give atropine 0.5-1 mg IV (repeat q3-5min, max 3 mg) 1, 2
   • Avoid catecholamines if chest pain suggests ischemia 1, 2
   • Consider transcutaneous pacing if atropine fails 2
5. Permanent pacemaker if symptoms persist after reversible causes addressed 1, 2