Approach to
Bradycardia
Last week
we discussed an approach to bradycardia at morning report.
When there
is an abnormality in a vital sign, the first step is to ensure stability.
1. Assess the ABCs, get monitors on, IV
access
a. Bradycardia is defined as a heart
rate less than 60 beats per minute
2. Ask yourself, is this unstable
bradycardia?
a. If yes à go down the unstable bradycardia
ACLS algorithm
b. If no à there is time to perform a focused
history, physical and get investigations
3. How do you define unstable bradycardia?
a. Bradycardia that is causing one of
the following symptoms:
i.
Hypotension
ii.
Acute
altered mental status
iii.
Signs
of shock
iv.
Ischemic
chest discomfort
v.
Acute
heart failure
4. If there is unstable bradycardia,
follow the ACLS algorithm including considering:
a. Atropine
b. Transcutaneous pacing
c. Dopamine or epinephrine infusions
5. If it is stable bradycardia, there
is time to collect more information with a focused history, physical and get
investigations
6. An ECG is a key investigation!
7. Two main question are:
a. What type of rhythm is it?
b. What is causing the bradycardia?
Rhythms associated with bradycardia
Bradycardia
is an umbrella term that means that the heart rate is less than 60 beats per
minute. But there can be several different rhythms that can cause a heart rate
of less than 60 bpm.
-
Bradycardias
can be classified narrow complex or wide complex (and as regular or irregular)
Narrow complex bradycardias
-
Sinus
bradycardia
-
Junctional
bradycardia
-
Sinus-node
dysfunction
-
Second
degree AV block, type I or II
-
Complete
AV block (third degree AV block) with junctional escape
-
Atrial
flutter or atrial fibrillation with high degree block/slow ventricular response
Wide complex bradycardia
-
Idioventricular
rhythm
-
Complete
AV block (third degree AV block) with ventricular escape
-
Any
other causes of narrow complex bradycardia with aberrancy or bundle branch
block
Causes of bradycardia
There are
many causes of bradycardia. While not a fully inclusive list, causes can
include:
Cardiac disease
-
Myocardial
ischemia/MI
-
Myocarditis
-
Cardiomyopathies
-
Congenital
disorders (such as muscular dystrophy)
Metabolic
-
Electrolyte
disturbances (i.e. hypo- or hyper-kalemia)
-
Hypothyroidism
-
Hypothermia
Drugs
-
Medications
(i.e. digoxin, beta blockers, calcium channel blockers, etc)
-
Toxidromes
(cholinergic)
Iatrogenic
-
Post-cardiac
procedure, surgery or transplantation
Infectious
-
Endocarditis
-
Lyme
disease
-
Typhoid
fever
-
Chagas
Disease
Autoimmune
-
Systemic
lupus erythematosus
-
Rheumatoid
arthritis
-
Scleroderma
Infiltrative
-
Sarcoidosis
-
Amyloidosis
-
Hemochromatosis
Physiological causes
-
Athletes
-
Vagal
stimuli
Other causes
-
Hypoxia
-
Obstructive
Sleep Apnea
-
Increased
intracranial pressure (i.e. Cushing response)
References:
1. Mangrum JM, DiMarco JP. The
evaluation and management of bradycardia. N Engl J Med. 2000;342(10):703-9.
2. Life in the Fastlane. Bradycardia. https://lifeinthefastlane.com/resources/bradycardia-ddx/
