Bradycardia Assessment and Initial Management
Immediate Assessment: Determine if Bradycardia is Symptomatic
The single most critical determination is whether the bradycardia is causing symptoms—asymptomatic bradycardia, regardless of heart rate (even as low as 37–40 bpm), requires no treatment, monitoring, or intervention. 1, 2
Cardinal Symptoms Requiring Immediate Action (Class I)
Assess for these specific signs of hemodynamic compromise:
- Altered mental status (confusion, decreased responsiveness) 2, 3
- Syncope or presyncope (most debilitating symptom, particularly when causing trauma) 2, 3
- Ischemic chest pain or angina pectoris (indicating inadequate coronary perfusion) 2, 3
- Acute heart failure signs (pulmonary edema, jugular venous distension, dyspnea) 2, 3
- Hypotension (systolic BP <90 mmHg, cool extremities, delayed capillary refill) 2, 3
- Cardiogenic shock (end-organ hypoperfusion) 2, 3
Less Urgent but Clinically Relevant Symptoms
Initial Diagnostic Workup (Class I)
Immediate Steps
- Obtain 12-lead ECG to document rhythm, rate, PR interval, QRS duration, and bundle-branch block patterns—but do not delay treatment in unstable patients 1, 2, 3, 4
- Attach cardiac monitor and establish continuous rhythm monitoring 3, 4
- Establish IV access for medication administration 3
- Assess oxygenation: provide supplemental oxygen if hypoxemic (hypoxemia is a common reversible cause) 3, 4
- Measure blood pressure and oxygen saturation 3
Rhythm-Symptom Correlation Strategy
Correlation between documented bradycardia and symptoms is the gold standard before any permanent intervention. 1, 2
| Symptom Frequency | Monitoring Strategy | Class |
|---|---|---|
| Daily or near-daily symptoms | 24–72 hour Holter monitor | Class I [1,2] |
| Weekly symptoms | 7–30 day event recorder | Class I [1,2] |
| Monthly or less frequent symptoms (>30 days between episodes) | Implantable loop recorder (diagnostic yield 43–50% at 2 years, ~80% at 4 years) | Class IIa [1,2] |
Identify and Treat Reversible Causes (Class I—Highest Priority)
Before any pharmacologic or device therapy, systematically evaluate and treat reversible etiologies. 1, 2, 3
| Reversible Cause | Evaluation | Treatment |
|---|---|---|
| Medications (β-blockers, non-dihydropyridine CCBs, digoxin, amiodarone, sotalol, ivabradine) | Review drug list | Discontinue or reduce dose [1,2,3,4] |
| Hypothyroidism | TSH, free T4 | Initiate levothyroxine replacement [1,2,3] |
| Electrolyte abnormalities | Serum K⁺, Mg²⁺ | Correct hyper-/hypokalemia, hypomagnesemia [1,2,3] |
| Acute myocardial infarction (especially inferior MI) | Cardiac biomarkers, ECG changes | Treat ischemia; bradycardia often resolves [1,2,3] |
| Obstructive sleep apnea | Clinical suspicion, sleep study | Initiate CPAP therapy [1,2,3] |
| Elevated intracranial pressure | Neuroimaging, neurologic exam | Neurosurgical consultation [1,2] |
| Hypothermia | Core temperature | Active rewarming [1] |
| Infections (Lyme disease, viral myocarditis) | Clinical context, serology | Appropriate antimicrobial therapy [1] |
Acute Pharmacologic Management
First-Line: Atropine (Class I/IIa)
Atropine 0.5–1 mg IV bolus, repeat every 3–5 minutes to a maximum total dose of 3 mg. 1, 2, 3, 4
Critical caveats:
- Doses <0.5 mg may paradoxically worsen bradycardia 1, 2
- Absolute contraindication (Class III—Harm): Do NOT give atropine to heart transplant recipients without autonomic reinnervation—risk of paradoxical high-grade AV block 1, 2, 3, 4
- Most effective for sinus bradycardia and AV nodal blocks; less effective for infranodal (wide-complex) blocks 2
Second-Line: Catecholamine Infusions (Class IIb)
Use when atropine fails AND patient has low risk for coronary ischemia. 1, 2, 3
| Agent | Dose | Notes |
|---|---|---|
| Dopamine | 5–20 µg/kg/min IV, titrate by 5 µg/kg/min every 2 min | Preferred for combined chronotropic and inotropic support [1,2,3,4] |
| Epinephrine | 2–10 µg/min IV or 0.1–0.5 µg/kg/min IV | Titrate to target heart rate [1,2,3,4] |
| Isoproterenol | 20–60 µg IV bolus or 1–20 µg/min infusion | Pure β-agonist; avoid in coronary ischemia [1,2] |
Special Situations: Specific Antidotes (Class I)
| Overdose/Situation | Treatment |
|---|---|
| Calcium-channel blocker toxicity | 10% calcium chloride 1–2 g IV q10–20 min OR 10% calcium gluconate 3–6 g IV q10–20 min [1,2] |
| Beta-blocker or CCB overdose | Glucagon 3–10 mg IV bolus, then 3–5 mg/h infusion [1,2] |
| Inferior MI with high-grade AV block | Aminophylline 250 mg IV bolus [1,2] |
| Heart transplant or spinal cord injury | Theophylline 100–200 mg IV (max 250 mg) or aminophylline infusion [2,4] |
Temporary Pacing (Bridge Therapy)
Transcutaneous Pacing (Class IIa/IIb)
Indicated for severe symptoms or hemodynamic compromise unresponsive to atropine, serving as a bridge to transvenous or permanent pacing. 1, 2, 3, 4
- Confirm mechanical capture by pulse palpation or arterial waveform—electrical capture on ECG alone is insufficient 4
- Provide adequate sedation/analgesia for conscious patients 4
- Limitations: painful, less reliable capture 2
Transvenous Pacing (Class IIa)
Indicated for persistent hemodynamic instability refractory to medical therapy until permanent pacemaker placement or resolution of reversible cause. 2, 4
- Complication rate 14–40%: venous thrombosis (18–85% with femoral approach), pulmonary emboli, arrhythmias, loss of capture, perforation 2, 4
- Increases risk of permanent pacemaker infection 2
When NOT to Pace (Class III—Harm)
- Asymptomatic bradycardia 2, 4
- Minimal or infrequent symptoms without hemodynamic compromise 2, 4
- Physiologic sleep-related bradycardia 2, 4
- Physiologic bradycardia in athletes or young healthy individuals 2, 4
Indications for Permanent Pacemaker
Class I (Strong Recommendation)
- Symptomatic bradycardia persisting after reversible causes have been excluded or adequately treated 1, 2, 3
- High-grade AV block (Mobitz II or third-degree) with symptoms 1, 2, 3
- Bradycardia caused by essential guideline-directed medical therapy with no alternative treatment 2
Class IIa (Reasonable)
- Tachy-brady syndrome with symptoms attributable to bradycardia 2
- Symptomatic chronotropic incompetence 2
Class III (Not Indicated)
Electrophysiology Study (EPS)
EPS may be considered (Class IIb) when symptoms are present and noninvasive testing is nondiagnostic, particularly in patients with structural heart disease or abnormal baseline ECG (bundle-branch block, prior MI). 1, 2
- NOT indicated (Class III) in asymptomatic patients 1, 2
- Higher diagnostic yield in patients with history of heart disease or abnormal ECG 1
Common Pitfalls to Avoid
- Do NOT treat asymptomatic bradycardia based solely on heart rate numbers 2
- Do NOT implant a permanent pacemaker before fully evaluating and correcting reversible causes 2
- Do NOT administer atropine doses <0.5 mg (may worsen bradycardia) 1, 2
- Do NOT give atropine to heart transplant patients 1, 2, 3, 4
- Do NOT fail to document clear symptom-rhythm correlation prior to permanent pacing 2
- Do NOT admit or continuously monitor truly asymptomatic individuals 2
- Do NOT delay treatment to obtain 12-lead ECG in unstable patients 3
Special Populations
Elderly Patients (≥70 years)
Age alone does not preclude pacing if symptoms are present and reversible causes have been excluded; decisions should incorporate functional status, life expectancy, and quality-of-life priorities. 2
Athletes and Young Healthy Individuals
Resting rates of 40–50 bpm (awake) and 30 bpm during sleep are physiologic; occasional sinus pauses or type I AV block during sleep are normal findings. 2, 4