Source: Sanoski CA, Bauman
JL. The Arrhythmias. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells
BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic
Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=7972803.
Accessed June 30, 2012.
- Abnormally slow heart rate (<60 beats/min
- Sinus bradycardia
- Sick sinus syndrome
- Atrioventricular (AV) block
- Vasovagal syndrome
- Usually results from impaired sinoatrial (SA) node function
or conduction abnormalities between SA node and atrium, or within
AV node or intraventricular conduction pathways.
- Sinus bradycardia can be due to heart disease, medications,
or normal causes (e.g., in trained athletes).
- Sick sinus syndrome caused by malfunction of SA node from
organic heart disease or normal aging process.
- AV block caused by slowed or blocked conduction of electrical
impulses in AV conduction system.
- β-Blockers, digoxin, or nondihydropyridine
calcium antagonists may cause AV block, primarily in AV nodal area.
- Vasovagal syncope thought to be neurally mediated process
involving stimulation of cardiac mechanoreceptors (Bezold-Jarisch
- Frequency of sinus bradycardia unknown.
- Frequency of sick sinus syndrome in patients with heart disease
estimated to be 3 in 5000.
- Advancing age
- Drugs (e.g., central α2 agonists,
cholinesterase inhibitors, calcium channel blockers, digoxin, lithium, β-blockers)
- Heart disease (e.g., myocardial infarction)
- Electrolyte imbalances
- Sleep apnea
- Head injury
- Toxin exposure
- Many bradycardias asymptomatic (e.g., in trained athletes).
- Symptoms associated with hypotension (e.g., dizziness, syncope,
- Vasovagal syndrome may cause syncope.
- If LV dysfunction exists, patients may experience worsening
heart failure (HF) symptoms.
- Signs: Pulse <60 beats/min in adults.
- Performed if underlying causes suspected (e.g., hypothyroidism,
- Electrocardiogram (ECG) findings categorize AV block into
first-, second-, or third-degree block.
- Holter monitoring may be used to document the relationship
of bradycardia with symptoms.
- Electrophysiologic studies may be performed for accurate localization
of AV block.
- Identify and correct underlying causes.
- Resolve symptoms.
- Prevent recurrences.
- Avoid complications from surgical procedures and medications.
- Asymptomatic sinus bradyarrhythmias do not usually require
- Discontinue exacerbating medications, if feasible.
- Permanent ventricular pacemaker is long-term treatment of
choice for most patients with significant symptoms.
- Vasovagal syncope
- Oral β-blockers
- Other drugs (with or without β-blockers)
- Anticholinergics (scopolamine patches, disopyramide)
- α-Adrenergic agonists (midodrine)
- Adenosine analogues (theophylline, dipyridamole)
- Selective serotonin reuptake inhibitors (sertraline, paroxetine)
- Atrioventricular block
- Give atropine (0.5
mg IV every 3–5 minutes, up to 3 mg total dose) for patients
with Mobitz II or third-degree AV block who develop signs/symptoms
of poor perfusion (e.g., altered mental status, chest pain, hypotension,
- Epinephrine (2–10 mcg/min) or dopamine (2–10
mcg/kg/min) IV infusion if atropine fails.
- Assess heart rate, blood pressure, and resolution of symptoms.
- Observe for side effects if medications are used.
- Prognosis favorable when appropriate ...