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Symptomatic Bradycardia

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Rules for 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. PR interval is consistent.
QRS ComplexMeasures less than 0.12 seconds.

Table 10

Rules for First Degree Heart Block

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.
PR 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/Mobitz I)

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 lower 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 P waves that do not have a QRS complex.
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)

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.
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 ComplexMeasures less than 0.12 seconds.

Table 13

Rules for 3rd
Degree AV Block

Complete Heart Block

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 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

  • Constant PR intervals (may be prolonged) before a random QRS is dropped

Third Degree AV Block

  • P waves and QRS complex are not coordinated with each other
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