ACLS: Bradycardia – A Guide for Junior Doctors

Bradycardia, defined as a heart rate less than 60 beats per minute (bpm), can range from benign to life-threatening. As a junior doctor, understanding the nuances of identifying and managing bradycardia is essential, especially in an emergency setting where rapid assessment and decision-making are critical.

History Taking: Questions to Ask

When faced with a patient presenting with bradycardia, a thorough history is your first step. Key areas to cover include:

·     Symptoms:

·      Dizziness, syncope, or near-syncope? These can indicate poor perfusion.

·      Fatigue, weakness? This may be a subtle sign of decreased cardiac output.

·      Chest pain or dyspnea? Always assess for ischemia or heart failure.

·      Palpitations? Ask about irregular heartbeats, which may suggest an underlying arrhythmia.

·     Onset and Duration:

·      When did the symptoms start? Were they sudden or gradual?

·      Has the patient experienced intermittent episodes of bradycardia or a continuous slow heart rate?

·      Past Medical History:

·      Previous heart disease (e.g., myocardial infarction, heart failure)?

·      History of arrhythmias or any implanted devices like pacemakers?

·      Any history of hypothyroidism (a common cause of bradycardia)?

·      Any recent infections or fevers that could suggest myocarditis?

·     Medications:

·      Are they taking beta-blockers, calcium channel blockers, digoxin, or other medications that can cause bradycardia?

·      Any over-the-counter drugs or herbal supplements that might be contributing?

·     Social History:

·      Assess for drug or alcohol use, which can affect heart rate.

·      Recent exercise or endurance training, as athletes often have lower resting heart rates.

·     Family History:

·      Any history of sudden cardiac death, arrhythmias, or genetic conditions like long QT syndrome?

Examination Findings

During your physical exam, look for signs that might give clues to the underlying cause of bradycardia:

·      General Appearance:

·      Does the patient appear well-perfused, or are they pale, sweaty, or cyanotic?

·      Look for signs of shock: hypotension, altered mental status, or cool extremities.

·     Pulse:

·      Check the rate and rhythm. Is the pulse regular or irregular?

·      Assess if the bradycardia is relative to the clinical situation (e.g., inappropriate bradycardia in shock).

·      Cardiac Examination:

·      Auscultate for murmurs, gallops (S3, S4), or signs of heart failure.

·      Check for jugular venous distension (JVD) as a sign of congestive heart failure.

·     Lungs:

·      Look for basal crackles or wheezing, which might indicate fluid overload or pulmonary edema in cases of heart failure.

·     Neurological Exam:

·      Assess for altered mental status, focal neurological deficits, or signs of poor cerebral perfusion.

·      Signs of Specific Conditions:

·      Hypothyroidism: Check for dry skin, delayed reflexes, or periorbital edema.

·      Toxins: Look for signs of drug toxicity or overdose (e.g., pinpoint pupils for opioids).

Investigations to Order

1.  Electrocardiogram The most crucial first investigation to assess bradycardia. Key findings to look for:

o   Sinus bradycardia: Regular rhythm, but slow rate.

o   Heart blocks: Look for 1st, 2nd (Mobitz type I and II), or 3rd-degree heart blocks.

o   Ischemia: ST-elevation or depression may suggest an underlying ischemic cause.

o   Toxicities: Digoxin toxicity can cause characteristic “scooped” ST segments.

2.Blood Tests:

o   Electrolytes: Hypokalemia or hyperkalemia can cause bradycardia.

o   Thyroid function tests: To rule out hypothyroidism.

o   Cardiac enzymes: If you suspect myocardial infarction.

o   Toxicology screen: For potential drug overdoses.

3.Imaging:

o   Chest X-ray: To assess for cardiomegaly, pulmonary edema, or other signs of heart failure.

o   Echocardiogram: To assess for structural heart disease, valvular issues, or poor left ventricular function.

4.Further Cardiac Monitoring:

o   If the bradycardia is intermittent, consider Holter monitoring or an event recorder.

Management Plan

Management of bradycardia depends on whether the patient is stable or unstable. Follow the Advanced Cardiovascular Life Support (ACLS) guidelines:

1.     Identify and Treat the Cause:

o   Stop any offending drugs (e.g., beta-blockers, calcium channel blockers).

o   Correct electrolyte imbalances (e.g., potassium, calcium).

o   Treat underlying causes like hypothyroidism or myocardial infarction.

2.     ACLS for Unstable Bradycardia:If the patient has signs of poor perfusion (hypotension, altered mental status, chest pain, or signs of shock):

o   Atropine 0.5 mg IV, repeat every 3-5 minutes (max dose: 3 mg).

o   If atropine is ineffective, consider transcutaneous pacing.

o   Dopamine infusion (2-10 mcg/kg/min) or epinephrine infusion (2-10 mcg/min) may also be used to support heart rate and perfusion.