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In this lesson, we're going to cover bradycardia, including some things to be aware of when dealing with bradycardic patients, types of bradycardia, and some information on the best courses of treatment to resolve that patient's bradycardia. And at the end of the lesson, we'll dig a little deeper into the types of bradycardia.
Absolute bradycardia is defined as a pulse rate less than 60 beats per minute. During your patient assessment, it's important to determine whether any life-threatening signs and symptoms are present that have been caused by that bradycardia.
Bradycardia can present itself in several different cardiac rhythms, which include sinus bradycardia and varying degrees of AV heart blocks.
Pro Tip #1: Regardless of the patient's rhythm, if their heart rate is too slow and the patient has symptoms from that slow heart rate, bradycardia should be treated to increase the heart rate and improve perfusion.
For patients who are asymptomatic, you should continue to provide care with close monitoring and choose which appropriate treatment and care should be given.
The primary treatment for symptomatic bradycardia includes the following:
1. Administration of supplemental oxygen if pulse oximetry is below 94 percent and establish IV access.
2. Monitor the patient's ECG rhythm.
3. Obtain a 12 lead as soon as possible, but don't delay therapy to get it.
4. Administration of atropine at 1 mg via rapid IV push to increase the patient's heart rate.
5. If atropine is proving to be ineffective, consider transcutaneous pacing.
Pro Tip #2: If there are serious signs and symptoms that the patient is unresponsive, the first line of treatment should be transcutaneous pacing rather than atropine.
6. Consider the administration of other medications such as:
a. An epinephrine infusion at between 2 to 10 mcg per minute
b. A dopamine infusion at between 5 and 10 mcg per kg per minute
Warning: If you are dealing with a conscious patient who needs transcutaneous pacing, you may want to consider sedation first to help alleviate their discomfort.
Some patients may present with relative bradycardia when their heart rate is over 60 beats per minute, but they present with a low blood pressure or decreased level of consciousness. In these cases, the same interventions would be required as a patient with absolute bradycardia.
An Additional Word About Bradycardia
As already mentioned above, bradycardia is defined by a heart rate of less than 60 beats per minute. This can result in a decrease in cardiac output, which may lead to a patient becoming clinically unstable if the patient's heart cannot compensate for the decreased rate by increasing its ability to pump more blood with each heartbeat.
Also mentioned above, absolute bradycardia is defined as any heart rate less than 60 beats per minute. While relative bradycardia is a term used to describe a heart rate that is greater than 60 beats per minute but too slow given the patient's condition.
For example, the patient may have a heart rate of 70 beats per minute, while also experiencing altered mental status, hypotension, or other signs of hemodynamic compromise. This would be considered a clinically significant bradycardia because the heart rate is not adequate for their clinical condition.
Hypoxemia is a common cause of bradycardia. Other causes of bradycardia include medications, structural damage, and metabolic dysfunction, such as electrolyte abnormalities and thyroid disease. The ACLS algorithm is a guideline for the treatment of clinically significant bradycardia.
Sinus Bradycardia
Sinus bradycardia can result from excess vagal stimulation, which slows SA node discharge. This may result from hypoxia, structural heart disease, damage to the cardiac electrical conduction system, medications, such as beta-blockers and calcium channel blockers, and metabolic dysfunction.
The clinical significance of sinus bradycardia is that it can result in decreased cardiac output. ln those patients who routinely engage in aerobic exercise, sinus bradycardia could be a normal finding.
Idioventricular Rhythm
Idioventricular rhythms occur when a ventricular focus acts as the primary pacemaker for the heart. This is identified by a slow ventricular rate of 20 to 40 beats per minute and a wide and bizarre appearance of the QRS complexes.
Because atrial activity is absent, there are no P waves preceding each QRS complex.
The clinical significance of idioventricular rhythm is that it can result in decreased cardiac output and poor perfusion. In the absence of atrial contraction, a reduced volume of blood is ejected into the ventricles. In addition, the ventricular rate is slow, which may result in a reduced cardiac output.
Heart Blocks
As mentioned in the opening of this lesson, bradycardia can present itself in several different cardiac rhythms, which include varying degrees of atrioventricular (AV) heart blocks.
AV heart blocks are caused by delayed, inconsistent, or absent electrical conduction through the AV node. These are classified as first degree, second degree (Mobitz type l and II), and third-degree.
