Initial assessment (ABCDE)
The patient presents with bradycardia. An immediate systematic assessment should be performed according to the ABCDE approach, including airway, breathing, circulation, level of consciousness and skin assessment.
After this assessment, it is essential to determine whether the patient has symptoms or signs of severity.
Symptoms and severity criteria
In the absence of symptoms, and if sinus rhythm remains stable, discharge may be considered, with referral for outpatient investigations, including a 12-lead electrocardiogram, Holter monitoring, echocardiography, laboratory tests and follow-up in a cardiology clinic.
If the patient has symptoms or clinical deterioration — such as hypotension, syncope, myocardial ischaemia, heart failure or altered level of consciousness — or if recurrence occurs after treatment of reversible causes, intermediate measures should be initiated.
Initial treatment and intermediate measures
These may include administration of atropine, isoprenaline or adrenaline. In cases of acute myocardial infarction with atrioventricular block, aminophylline may be considered.
If symptoms persist, worsen or haemodynamic instability develops, cardiac pacing should be considered.
Reversible causes
At the same time, it is essential to identify and treat reversible causes. These include acute myocardial infarction, electrolyte abnormalities such as hyperkalaemia, hypokalaemia and hypoglycaemia, hypothyroidism, hypoxia or hypercapnia, as well as infections or post-infectious conditions such as Lyme disease, syphilis, leptospirosis, malaria and legionellosis.
Drug toxicity
In cases of calcium-channel blocker toxicity, calcium chloride or calcium gluconate may be administered. If necessary, insulin therapy may be included.
In beta-blocker toxicity, the drug of choice is glucagon, which may be complemented with insulin according to clinical evolution. In digoxin toxicity, specific antibodies should be used. In opioid intoxication, naloxone administration is indicated.
High risk of asystole
Bradycardia with a high risk of asystole — including recent asystole, Mobitz type II atrioventricular block, complete heart block with a wide QRS complex or ventricular pauses longer than 3 seconds — requires strict monitoring.
In the absence of an adequate response to initial measures, specialist support should be considered to initiate more advanced interventions.
Contraindications to atropine
Atropine is contraindicated in some clinical conditions, such as angle-closure glaucoma, paralytic ileus, prostatic hypertrophy, severe ulcerative colitis, toxic megacolon, myocardial ischaemia and myasthenia gravis.
Conclusion
The treatment of bradycardia should always be guided by the clinical presentation, identification of reversible causes and response to the measures instituted, with therapeutic escalation according to the severity of the clinical condition.
