Symptomatic Bradycardia

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Rules for Sinus Bradycardia

ACLS Sinus Bradycardia Rhythm

Figure 31

Regularity R-R intervals are regular, overall rhythm is regular.
Rate The rate is less than 60 bpm, but usually more than 40 bpm.
P Wave There is one P wave in front of every QRS. The P waves appear uniform.
PR Interval Measures between 0.12 and 0.20 seconds in duration. PRI is consistent.
QRS Complex Measures less than 0.12 seconds.

Table 10

Rules for First Degree

ACLS First Degree Rhythm

Figure 32

Regularity R-R intervals are regular, overall rhythm is regular.
Rate The rate depends on the underlying rhythm.
P Wave There is one P wave in front of every QRS. The P waves appear uniform.
P Interval Measures more than 0.20 seconds in duration. PRI is consistent.
QRS Complex Measures less than 0.12 seconds.

Table 11

Rules for 2nd Degree Type I AV Block (Wenkebach)

ACLS 2nd Degree Type 1 (Wenkebach) Rhythm

Figure 33

Regularity R-R interval is irregular, but there is usually a pattern to it. The R-R interval gets longer as the PR interval gets longer.
Rate The ventricular rate is usually slightly higher than the atrial rate due to some atrial beats not being conducted. The atrial rate is usually normal.
P Wave P waves are upright and uniform. Most complexes will have a P wave in front of them; however, there will be some that do not have a P wave.
PR Interval PR interval gets progressively longer until there is a dropped QRS complex.
QRS Complex Measures less than 0.12 seconds.

Table 12

Rules for 2nd Degree Type II AV Block (Mobitz II)

ACLS 2nd Degree Type 2 (Mobitz II) Rhythm

Figure 34

Regularity If there is a consistent conduction ratio, then the R-R interval will be regular. If the conduction ratio is not constant, the R-R interval will be irregular.
Rate The atrial rate is normal. The ventricular rate is slower, usually 1/2 to 1/3, slower than the atrial rate.
P Wave P waves are upright and uniform. There is not a QRS following every P wave.
P Interval PR interval can only be measured on conducted beats, and it is usually constant across the strip. It may or may not be longer than a normal PR interval (0.12 seconds
QRS Complex Measures less than 0.12 seconds.

Table 13

Rules for 3rd
Degree AV Block

Complete Heart Block

ACLS 3rd Degree AV Block (Complete Heart Block) Rhythm

Figure 35

Regularity R-R interval is regular. P-P interval is also regular.
Rate The atrial rate is regular and normally 60 to 100. Rate of QRS complexes is dependent on the focus. If the focus is ventricular, the rate will be 20 to 40. If the focus is junctional, the rate will be 40 to 60.
P Wave P waves are upright and uniform. There is not a QRS following every P wave.
PR Interval PR interval can only be measured on conducted beats, and it is usually constant across the strip. It may or may not be longer than a normal PR interval (0.12 seconds).
QRS Complex Interval may be normal but is more likely to be prolonged.

Table 14

Symptomatic Bradycardia

Bradycardia is defined as a heart rate of less than 60 beats per minute. While any heart rate less than 60 beats per minute is considered bradycardia, not every individual with bradycardia is symptomatic or having a pathological event. Individuals in excellent physical shape often have sinus bradycardia. Symptomatic bradycardia may cause a number of signs and symptoms including low blood pressure, pulmonary edema and congestion, abnormal rhythm, chest discomfort, shortness of breath, lightheadedness, and/or confusion. Symptomatic bradycardia should be treated with the ACLS Survey. If bradycardia is asymptomatic but occurs with an arrhythmia listed below, obtain a consultation from a cardiologist experienced in treating rhythm disorders.

Symptoms of Bradycardia

  • Shortness of breath
  • Altered mental status
  • Hypotension
  • Pulmonary edema/ congestion
  • Weakness/dizziness/ lightheadedness

Symptomatic Bradycardia Review

Sinus Bradycardia

  • Normal rhythm with slow rate

First Degree AV Block

  • PR interval is longer than 0.20 seconds

Type I Second Degree AV Block

  • PR interval increases in length until QRS complex is dropped

Type II Second Degree AV Block

  • PR interval is the same length until intermittently dropped QRS complex is dropped

Third Degree AV Block

  • PR and QRS are not coordinated with each other
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