Bradycardia resident survival guide

Bradycardia Resident Survival Guide Microchapters
Overview
Causes
Diagnosis
Treatment
Do's
Don'ts

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]: Associate Editor(s)-in-Chief: Ogheneochuko Ajari, MB.BS, MS [2]; Vidit Bhargava, M.B.B.S [3]

Overview

Bradycardia is defined as a sinus rhythm with a rate <60 beats per minute. A heart rate of <50 beats per minute is used as a working definition of bradycardia causing symptoms.. The evaluation of bradycardia includes assessment of heart rhythm, symptoms and associated medical conditions. Symptomatic bradycardias are treated by removal of underlying causes, medications (e.g. the use of atropine) or insertion of temporary or permanent pacemaker. Nevertheless, some asymtomatic bradycardias may require treatment to prevent complications.

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Hyperkalemia
• Hypoxia
• Inferior myocardial infarction
• Intracranial hypertension

Common Causes

• Carotid sinus hypersensitivity
• Medications

Diltiazem

Amiodarone

Amitriptyline

Beta-blockers

Cardiac glycosides

Clonidine

Dronedarone

Flecainide

Lithium

Methyldopa

Phenothiazines

Procainamide

Propafenone

Quinidine

Reserpine

Verapamil

• Sick sinus syndrome

Diagnosis

Shown below is an algorithm depicting the diagnosis of bradycardia

Characterize the symptoms: ❑ Palpitations ❑ Lightheadedness or Dizziness ❑ Dyspnea ❑ Chest pain ❑ Altered mental status ❑ Syncope ❑ Fatigue ❑ Exercise intolerance Obtain a detailed history: ❑ Age - commonly seen in the elderly due to: ♦ Disease in the sinus node ♦ AV nodal disease ♦ Age-related fibrosis and sclerosis ❑ Medication use ♦ Beta blockers ♦ Calcium channel blockers ♦ Digoxin ❑ Past medical history ♦ Infection ♦ Increased intracranial pressure ♦ Electrolyte disturbance ♦ Exposure to toxins ♦ Surgery ♦ Heart transplant ♦Sleep apnea ♦ Myocardial infarction ♦ Hypothyroidism

Examine the patient: ❑ Heart rate < 50/min ❑ Signs of increased work of breathing ♦ Tachypnea ♦ Intercostal retractions ♦ Suprasternal retractions ♦ Paradoxical abdominal breathing ❑ Signs of poor perfusion ♦ Hypotension ♦ Signs of shock

Consider alternative diagnosis: ❑ Ventricular bigeminy ❑ Frequent premature ventricular contractions (PVCs) ❑ Atrial fibrillation ❑ Blocked premature atrial contractions (PACs) ❑ Cardiac tamponade

Order tests: First initial test ❑ 12-lead ECG 12-lead ECG showing sinus bradycardia Other initial tests ❑ Holter monitoring- to evaluate ♦ Severe sinus bradycardia ♦ Sinus pauses ♦ Sinus arrest ♦ Second-or third-degree AV block ❑ Exercise stress testing - For diagnoses of sick sinus syndrome and ischemic heart disease ❑ Carotid sinus massage - to evaluate carotid sinus hypersensitivity ❑ Echocardiogram - For valvular heart disease Laboratory tests ❑ Thyroid function tests - Elevated TSH in hypothyroidism ❑ Basic metabolic panel - For electrolyte disturbances ❑ Cardiac enzymes - Creatine kinase, CK-MB and troponin ❑ Serum creatinine - Elevated in renal impairment ❑ Serum digoxin - for junctional bradycardia Other Investigations ❑ Tilt-table testing - Evaluation of autonomic system and diagnosis of neurocardiogenic syncope ❑ Electrophysiologic testing - to evaluate bradyarrhythmias

Treatment

Shown below is an algorithm depicting the treatment of bradycardia based on the 2010 AHA guidelines for cardiopulmonary resuscitation and emergency cardiovascular care.

Bradycardia confirmed Bradyarrhythmia seen with heart rate < 50/min

Identify and treat underlying cause: ❑ Maintain patent airway; assist breathing as necessary ❑ Oxygen (if hypoxemic) ❑ Cardiac monitor to identify rhythm ❑ Monitor blood pressure and oximetry ❑ IV access ❑ 12-lead ECG if available; don’t delay therapy

Bradyarrhythmia causing symptoms? ❑ Hypotension? ❑ Acutely altered mental status? ❑ Signs of shock? ❑ Ischemic chest discomfort? ❑ Acute heart failure?

Yes

No

Primary treatment option Atropine ❑ Administer a first dose 0.5 mg IV bolus ❑ Repeat every 3-5 minutes ❑ Administer a maximum dose of 3 mg

❑ Monitor and observe

Secondary treatment options If atropine ineffective: ❑ Administer dopamine infusion (2-10 mcg/kg/min) OR ❑ Administer epinephrine infusion (2-10 mcg/min) OR ❑ Proceed with transcutaneous pacing

❑ Consult to Cardiologist ❑ Consider transvenous pacing

Do's

• Prepare for transcutaneous pacing if perfusion is poor.
• Consider using sodium bicarbonate for severe metabolic acidosis.
• Use atropine with caution in the presence of myocardial ischemia because it increases oxygen demand and could worsen the ischemia.

Don'ts

• Do not delay pacing if the rhythm is Mobitz type II second degree block or third-degree AV block even if the patient is asymptomatic.
• Avoid using atropine in hypothermic patients with either bradycardia or Mobitz type II second degree AV block.
• Do not use atropine to treat bradycardia in cardiac transplant patients.
• Do not use atropine to treat Type II second degree and third degree heart blocks since their management requires transcutaneous/transvenous pacing.