Symptomatic Bradycardia-Slow Heart Rate

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Rules for Sinus Bradycardia

ACLS Rhythm - Sinus bradycardia

Figure 31

RegularityR-R intervals are regular, overall rhythm is regular.
RateThe rate is less than 60 bpm, but usually more than 40 bpm.
P WaveThere is one P wave in front of every QRS. The P waves appear uniform.
PR IntervalMeasures between 0.12 and 0.20 seconds in duration. PRI is consistent.
QRS ComplexMeasures less than 0.12 seconds.

Table 10

Rules for First Degree

ACLS Rhythm - First Degree

Figure 32

RegularityR-R intervals are regular, overall rhythm is regular.
RateThe rate depends on the underlying rhythm.
P WaveThere is one P wave in front of every QRS. The P waves appear uniform.
P IntervalMeasures more than 0.20 seconds in duration. PRI is consistent.
QRS ComplexMeasures less than 0.12 seconds.

Table 11

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

ACLS Rhythm - 2nd Degree Type 1

Figure 33

RegularityR-R interval is irregular, but there is usually a pattern to it. The R-R interval gets longer as the PR interval gets longer.
RateThe 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 WaveP 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 IntervalPR interval gets progressively longer until there is a dropped QRS complex.
QRS ComplexMeasures less than 0.12 seconds.

Table 12

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

ACLS Rhythm - 2nd Degree Type 2

Figure 34

RegularityIf 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.
RateThe atrial rate is normal. The ventricular rate is slower, usually 1/2 to 1/3, slower than the atrial rate.
P WaveP waves are upright and uniform. There is not a QRS following every P wave.
P IntervalPR 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 ComplexMeasures less than 0.12 seconds.

Table 13

Rules for 3rd
Degree AV Block

Complete Heart Block

ACLS Rhythm - 3rd Degree

Figure 35

RegularityR-R interval is regular. P-P interval is also regular.
RateThe 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 WaveP waves are upright and uniform. There is not a QRS following every P wave.
PR IntervalPR 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 ComplexInterval may be normal but is more likely to be prolonged.

Table 14

Symptomatic Bradycardia

Bradycardia is the condition where the heart beats at a rate less than 60 beats per minute. Though any heart rate pumping out less than 60 beats in a minute may be considered bradycardia, this isn’t always a point for concern. Even people who are physically fit can experience sinus bradycardia. Bradycardia is often indicative of low blood pressure, pulmonary edema and congestion, abnormal rhythm, discomfort in the chest, shortness of breath, lightheadedness, and/or confusion. On the other hand, symptomatic bradycardia should be attended to with the ACLS Survey. If this condition is asymptomatic but still happens within the arrhythmia illustrated in the following sections, rhythm disorders can easily be remedied by consulting with a cardiologist.

Symptoms of Bradycardia

  • Uneven breathing
  • Altered mental status
  • Pulmonary edema/congestion
  • Hypertension
  • Weakness/dizziness/lightheadedness

Symptomatic Bradycardia Review

Sinus Bradycardia

  • Slow rate with normal rhythm

First Degree AV Block

  • PR interval is longer than 0.20 seconds

Type I Second Degree AV Block

  • Interval of the PR 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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