Bradycardia
Bradycardia refers to a heart rate of less than 60 beats/minute. It occurs normally in young adults, trained athletes, and elderly people as well as during sleep. It’s also a normal response to vagal stimulation caused by coughing, vomiting, or straining during defecation. When bradycardia results from these causes, the heart rate rarely drops below 40 beats/minute. However, when it results from pathologic causes, such as cardiovascular disorders, the heart rate may be slower.
By itself, bradycardia is a nonspecific sign. However, in conjunction with such symptoms as chest pain, dizziness, syncope, arrhythmias, and shortness of breath, it can signal a life-threatening disorder.
Act Now: Depending on the accompanying signs and symptoms, the patient with bradycardia may require immediate emergency care. For symptomatic bradycardia, atropine I.V. may be ordered, a transcutaneous pacemaker may be required, and full cardiorespiratory arrest may occur.
Assessment
History
After detecting bradycardia, check for related signs of life-threatening disorders before proceeding with a history. (See Managing severe bradycardia, page 62.) Determine if the patient or a family member has a history of a slow pulse rate. Check for underlying metabolic disorders, such as hypothyroidism, which can precipitate bradycardia. Obtain a medication history and make sure that the prescribed schedule and dosage is followed.
Physical examination
Monitor the patient’s vital signs, temperature, pulse, respirations, blood pressure, and oxygen saturation. If he’s on a cardiac monitor, frequently assess cardiac rhythm and note changes.
Assess for changes in the patient’s level of consciousness (LOC) or respiratory status.
Pediatric pointers
Heart rates are normally higher in children than in adults. Fetal bradycardia — a heart rate of less than 120 beats/minute — may occur during prolonged labor or complications of delivery, such as compression of the umbilical cord, partial abruptio placentae, and placenta previa. Intermittent bradycardia, sometimes accompanied by apnea, commonly occurs in premature neonates. Bradycardia rarely occurs in full-term neonates or children. However, it can result from congenital heart defects, acute glomerulonephritis, and transient or complete heart block associated with cardiac catheterization or cardiac surgery.
Geriatric pointers
Sinus node dysfunction is the most common bradyarrhythmia encountered among the elderly. A patient with this disorder may have as his chief complaint fatigue, exercise intolerance, dizziness, or syncope. If the patient is asymptomatic, no intervention is necessary. A symptomatic patient, however, requires careful scrutiny of his drug therapy. Beta-adrenergic blockers, verapamil, diazepam, sympatholytics, antihypertensives, and some antiarrhythmics have been implicated; symptoms may clear when these drugs are discontinued. Pacing is usually indicated in the patient with symptomatic bradycardia lacking a correctable cause.
Medical causes
Cardiac arrhythmias
Depending on the type of arrhythmia and the patient’s tolerance of it, bradycardia may be transient or sustained, benign, or life threatening. Related findings include hypotension, palpitations, dizziness, weakness, syncope, and fatigue.
Cardiomyopathy
Cardiomyopathy is a potentially life-threatening disorder that may cause transient or sustained bradycardia. Other findings include dizziness, syncope, edema, fatigue, jugular vein distention, orthopnea, dyspnea, and peripheral cyanosis.
Cervical spinal injury
Bradycardia may be transient or sustained, depending on the severity of the injury. Its onset coincides with sympathetic denervation. Associated signs and symptoms include hypotension, decreased body temperature, slowed peristalsis, leg paralysis, and partial arm and respiratory muscle paralysis.
Hypothermia
Bradycardia usually appears when the core temperature drops below 89.6° F (32° C). It’s accompanied by shivering, peripheral cyanosis, muscle rigidity, bradypnea, and confusion leading to stupor.
Hypothyroidism
Hypothyroidism causes severe bradycardia in addition to fatigue, constipation, unexplained weight gain, and sensitivity to cold. Related signs include cool, dry, thick skin; sparse, dry hair; facial swelling; periorbital edema; thick, brittle nails; and confusion leading to stupor.
Increased intracranial pressure (ICP)
Bradycardia occurs as a late sign of increased ICP along with rapid respiratory rate, elevated systolic pressure, decreased diastolic pressure, and widened pulse pressure. Associated signs and symptoms include persistent headache, projectile vomiting, decreased LOC, and fixed, unequal and, possibly, dilated pupils.
Myocardial infarction (MI)
Sinus bradycardia is the most common arrhythmia associated with an acute MI. Accompanying signs and symptoms of an MI include an aching, burning, or viselike pressure in the chest that may radiate to the jaw, shoulder, arm, back, or epigastric area; nausea and vomiting; cool, clammy, and pale or cyanotic skin; anxiety; and dyspnea. Blood pressure may be elevated or depressed. Auscultation may reveal abnormal heart sounds.
Other causes
Diagnostic tests
Cardiac catheterization and electrophysiologic studies can induce temporary bradycardia.
Drugs
Beta-adrenergic blockers and some calcium channel blockers, cardiac glycosides, topical miotics (such as pilocarpine), protamine, quinidine and other antiarrhythmics, and sympatholytics may cause transient bradycardia. Failure to take thyroid replacements may also cause bradycardia.
Invasive treatments
Suctioning can induce hypoxia and vagal stimulation, causing bradycardia. Cardiac surgery can cause edema or damage to conduction tissues, causing bradycardia.
Nursing considerations
Continue to monitor the patient’s vital signs frequently. Stay especially alert for changes in his cardiac rhythm, respiratory rate, and LOC.
Prepare the patient for laboratory tests, which can include complete blood count; cardiac enzyme, serum electrolyte, blood glucose, blood urea nitrogen, arterial blood gas, and blood drug levels; thyroid function tests; and a 12-lead electrocardiogram. If appropriate, prepare the patient for 24-hour Holter monitoring.
Patient teaching
Explain all tests and procedures to the patient and his family. Explain the need for cardiac monitoring and common alarms that may be heard. Teach the patient and his family how to take a radial pulse.
Pictures
Book Source Details
- Book Title: Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series, Copyright © 2007 Lippincott Williams & Wilkins.
Other Book Chapters Related to Slow heartbeat
Read excerpts from these other book chapters related to Slow heartbeat:
Medical Books Excerpts
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- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
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- "Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series" (2007)
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- Murmurs
- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
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- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
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- Murmurs
- "Nursing: Interpreting Signs and Symptoms" (2007)
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- "Differential Diagnosis in Primary Care" (2007)
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Copyright Details: Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series, Copyright © 2008 Williams & Wilkins.
More About Causes of Slow heartbeat
» Next page: Pulsus paradoxus [Paradoxical pulse] (Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series)
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