Symptomatic Bradycardia: Adequate Versus Poor Perfusion
A heart rate of less than 50 beats per minute is classified as bradycardia, but bradycardia can be physiologically normal in some individuals. For instance, people who perform cardiovascular exercise regularly and are well conditioned often have a low resting heart rate.
In other instances, bradycardia may be caused by a variety of medical problems, such as abnormalities of the SA node, hypothermia, vagal stimulation and side effects of medication, such as beta blockers. Some patients can tolerate a heart rate of 50 beats a minute, but when the rate falls to less than 50 beats per minute, symptoms are more likely to occur.
Although some people with bradycardia may be asymptomatic, others may have symptoms related to the slow heart rate. The decision to implement treatment for bradycardia is based on the presence of symptoms and whether the patient’s perfusion is adequate or not.
Bradycardia and Adequate Perfusion
Patients with bradycardia must be assessed for symptoms and indications of adequate perfusion. Blood pressure and oxygen levels should be monitored and should be within normal range for the patient. Maintaining a normal level of consciousness is also a sign that perfusion may be adequate. Patients should also be asked if they are experiencing dizziness or fatigue, as these may be symptoms of poor perfusion.
If the patient has adequate perfusion, he may not need immediate or emergency treatment. Close monitoring is needed to identify a change in status as soon as it occurs. Continued pulse oximetry and cardiac monitoring may be useful to identify changes quickly. A 12 lead EKG should be performed in order to better define the rhythm. In patients who are hemodynamically stable, attention should be focused on the cause of bradycardia.
Signs of Poor Perfusion
Bradycardia may lead to signs of poor perfusion in some instances. Signs may include an altered level of consciousness, which may be due to hypotension. When determining level of consciousness it is important to consider the patient’s baseline level of functioning. Even if a patient has a history of dementia or confusion, worsening of their condition warrants investigation.
A decreased oxygen level is also a sign of poor perfusion. Although pulse oximetry can be used to assess oxygen level, an arterial blood gas is more precise. Evaluating pulse oximetry is a quick and noninvasive way to monitor oxygen saturation, but it can be difficult to get an accurate reading in patients who have poor perfusion.
Some patients with symptomatic bradycardia may become dizzy, weak, fatigued or faint. A decrease in blood pressure, diminished peripheral pulses and slow capillary refill may also indicate poor perfusion. The skin may be cool to the touch and cyanosis may be present. Ischemic chest pain, which varies in severity, may also develop.
Severe symptoms may also develop, including signs of congestive heart failure and respiratory distress. Pulmonary congestion can occur, which may lead to increased work of breathing. Signs of increased work of breathing or respiratory distress include retractions, use of accessory muscles, an increased respiratory rate and abdominal breathing.
Treatment for Symptomatic Bradycardia with Poor Perfusion>
When a patient has bradycardia with signs of poor perfusion, treatment is recommended. Bradycardia with poor perfusion can be life-threatening in some cases.
Initial treatment includes airway support to make sure the patient is ventilating adequately. Increased work of breathing and fatigue can lead to an inability to maintain adequate gas exchange. Supplemental oxygen should be administered if the patient’s oxygen level is low. The patient should be placed on a cardiac monitor, and a 12 lead ECG should be obtained.
Symptomatic bradycardia is often treated initially with atropine. It is important to note that atropine may not be effective in some types of bradycardia. For example, atropine may not be effective in treating complete AV blocks.
If symptomatic bradycardia is not responsive to atropine, an intravenous infusion of dopamine or epinephrine may be administered. As an alternative to epinephrine or dopamine administration, transcutaneous pacing may be attempted.
Transcutaneous pacing uses electrical energy in order to stimulate the contraction of the heart. The current delivered is much less than used in defibrillation or cardioversion. In some instances of symptomatic bradycardia with poor perfusion, transcutaneous pacing may be the treatment of choice if the patient is severely symptomatic, if atropine failed or if atropine is contraindicated. Long-term treatment for symptomatic bradycardia may include insertion of a permanent pacemaker.
NYU Langone Medical Center. Bradycardia. http://cvi.med.nyu.edu/conditions-we-treat/conditions/bradycardia-bradyarrhythmia Accessed September 2014.
Mayo Clinic Bradycardia. http://cvi.med.nyu.edu/conditions-we-treat/conditions/bradycardia-bradyarrhythmia Accessed September 2014.
Link, M. Arkins D. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010. http://circ.ahajournals.org/content/122/18_suppl_3/S706.full#sec-24 Accessed September 2014.
2016 American Heart Association Advanced Cardiac Life Support Provider Manual. pp 120-128