Skip to Main Content

++

SOURCE

+

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. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146057036. Accessed March 28, 2017.

++

CONDITION/DISORDER SYNONYM

++

  • Bradycardias.

++

DEFINITION

++

  • Abnormally slow heart rate (<60 beats/min in adults).

++

ETIOLOGY

++

  • Sinus bradycardia.

  • Sick sinus syndrome.

  • Atrioventricular (AV) block.

  • Vasovagal syndrome.

++

PATHOPHYSIOLOGY

++

  • 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 (eg, 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 reflex).

++

EPIDEMIOLOGY

++

  • Frequency of sinus bradycardia unknown.

  • Frequency of sick sinus syndrome in patients with heart disease estimated to be 3 in 5000.

++

RISK FACTORS

++

  • Advancing age.

  • Hypothyroidism.

  • Drugs (eg, central α2 agonists, cholinesterase inhibitors, calcium channel blockers, digoxin, lithium, β-blockers)

  • Heart disease (eg, myocardial infarction)

  • Electrolyte imbalances.

  • Sleep apnea.

  • Head injury.

  • Hypothermia.

  • Hypoglycemia.

  • Toxin exposure.

++

CLINICAL PRESENTATION

++
SIGNS AND SYMPTOMS
++

  • Many bradycardias asymptomatic (eg, in trained athletes).

  • Symptoms associated with hypotension (eg, dizziness, syncope, fatigue, confusion).

  • Vasovagal syndrome may cause syncope.

  • If LV dysfunction exists, patients may experience worsening heart failure (HF) symptoms.

  • Signs: Pulse <60 beats/min in adults.

++

DIAGNOSIS

++
LABORATORY TESTS
++

  • Performed if underlying causes suspected (eg, hypothyroidism, electrolyte imbalances).

++
DIAGNOSTIC PROCEDURES
++

  • Vagal maneuvers, carotid sinus massage, exercise for AV node bradyarrhythmias.

  • Electrocardiogram (ECG) findings categorize AV block into first-, second-, or third-degree block.

  • Holter monitoring (long-term recording) may be used to document the relationship of bradycardia with symptoms.

  • Electrophysiologic studies may be performed for accurate localization of AV block.

++

DESIRED OUTCOMES

++

  • Identify and correct underlying causes.

  • Resolve symptoms.

  • Prevent recurrences.

  • Avoid complications from surgical procedures and medications.

++

TREATMENT: GENERAL APPROACH

++

  • Asymptomatic sinus bradyarrhythmias do not usually require intervention.

++

TREATMENT: NONPHARMACOLOGIC THERAPY

++

  • Discontinue exacerbating medications, if feasible.

  • Permanent ventricular pacemaker is long-term treatment of choice for most patients with significant symptoms or those that are drug-refractory.

  • Temporary transvenous pacemakers will often be utilized for patients with an acute MI and evidence of a new AV block or conduction disturbance.

    ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.