Adult Bradycardia with a Pulse Algorithm

Goals for the Management of Adult Patients with Bradycardia

The team must succeed in the following goals to successfully manage bradycardia:

• Recognize and differentiate among several bradyarrhythmias:
  • Sinus bradycardia
  • First-degree AV block
  • Second-degree AV block: Type l (Wenckebach/Mobitz l)
  • Second-degree AV block: Type II(Mobitz II)
  • Third-degree AV block
• Recognize the signs and symptoms of symptomatic bradycardia.

Adult Bradycardia with a Pulse Algorithm Explained

This algorithm was created to present the steps for assessing and managing bradycardia with a pulse.

Box 1: Identification of Bradycardia

Bradycardias are heart rates < 60 bpm. When symptoms arise, the rate has usually fallen to < 50 bpm, and this is the working definition of bradycardia in the AHA algorithm.

Box 2: Identifying and Treating the Underlying Cause

Bradycardia causes a significant decrease in cardiac output, which leads to the signs and symptoms associated with bradyarrhythmia’s. It is vital to identify symptomatic bradycardia and begin treatment.

The responder must ensure that the patient’s airway is patent and administer oxygen if hypoxemic. The team monitors oxygen saturation continuously.

Cardiac monitoring should be initiated to identify the rhythm. It is essential to obtain IV or IO access for fluid and medication therapy. The team monitors the patient’s blood pressure and obtains a 12-lead ECG if that does not delay therapy.

Box 3: Bradycardia with Symptoms?

Untreated symptomatic bradycardia can lead to cardiac arrest. The team assesses for signs and symptoms of hemodynamic instability, including:

If the patient is hemodynamically stable, the team proceeds to Box 4; if hemodynamically unstable, they proceed to Box 5.

Hypotension, or low blood pressure, is one of the symptoms of bradycardia.

Box 4: Treatment if Asymptomatic

If the patient has no severe signs and symptoms associated with bradycardia, the team continues to monitor and observe. Continuous reassessment is essential, as the patient’s condition may deteriorate

Box 5: Treatment of Symptomatic Bradycardia

Medication, electrolyte imbalance, or myocardial disease secondary to acute MI can cause AV blocks. It is critical for the team to determine if the symptoms are caused by bradycardia. If not, they treat the underlying cause.

Treatment

Atropine, an anticholinergic drug, is the first-line drug for the treatment of symptomatic bradycardia. Atropine increases AV nodal conduction and thus improves the symptoms of bradycardia. This drug may be used to temporarily improve bradycardia until the team discovers a more permanent solution, such as pacing.

For this indication, atropine is given at a dose of 1.0 mg IV every 3 to 5 minutes up to a maximum of 3mg. It should be noted that atropine can cause further bradycardia if the clinician administers a dose <0.5 mg.

The first line of treatment for symptomatic bradycardia is atropine.

In cases of AMI, atropine should be used with caution because an increase in heart rate may step up myocardial oxygen demand and worsen the area of ischemia or infarction. Atropine is ineffective in heart transplant patients because they lack vagal innervation.

Bradyarrhythmias unlikely to respond to atropine are second-degree AV block, Mobitz type II, and third-degree AV block with a wide QRS complex that represents the block to be non-nodal. These blocks are likely to need transcutaneous pacing.

When treating bradycardia, it is important for the team to quickly recognize the bradycardia rhythms.

Sinus Bradycardia

Severe bradycardia, which brings an increased risk for cardiac arrest, will be accompanied by clinical signs such as hypotension, altered mental status, shock, chest discomfort, and acute heart failure.

Medications, electrolyte imbalances, or myocardial diseases secondary to AMI can cause AV blocks.

An ECG strip displays sinus bradycardia.

First-Degree AV block

First-degree heart blocks are often benign, and their ECG findings show an increased PR interval of more than 0.20 seconds.

The AV node maintains the sinus impulse longer than usual before it is conducted through the ventricles, but each impulse is conducted. Once into the ventricles, conduction proceeds normally.

Second-Degree AV Block Type I

In second-degree heart block (Wenckebach type I), the sinus node initiates impulses, and each one remains in the AV node a little longer than that preceding it until one is blocked completely. The conducted impulses travel through the ventricles normally.

Second-Degree AV Block Type II

Second-degree AV block (Mobitz Type II) is frequently associated with AMI and may transform into third-degree AV block, causing severe bradycardia. Immediate treatment in these cases is necessary. Impulses are blocked below the AV node within the His-Purkinje system, and this causes symptoms.

Characteristic in this ECG tracing is that the PR intervals have a fixed duration and the P waves have a constant rate. Conducted beats are followed by a QRS complex, and intermittently there are non-conducted P waves, after which the QRS is dropped.

This may or may not follow a pattern, but when there are a predictable number of P waves relative to QRS complexes, the rhythm will be described as a ratio, e.g., 2:1 Mobitz II block.

Third-Degree AV Block

The heart block occurs at the AV node in third-degree AV block. The atria beat at their own rate while a junctional or ventricular pacemaker determines the ventricular rate. The P waves march through and are unrelated to the QRS complexes, which occur at a slower rate, and this generally causes symptoms. Third-degree AV block may be permanent or transient.

Box 6: Further Considerations

The team considers expert consultations and transvenous pacing if symptomatic bradycardia persists.