DYSRHYTHMIA REVIEW
, DYSRHYTHMIA REVIEW
1. MU modules/resources
a. A Journey to Understanding Dysrhythmias-A Self-Paced Course (Basic ECG)
b. Emergency Nursing Orientation 3.0: Cardiovascular Emergencies Part I
c. Emergency Nursing Orientation 3.0: Cardiovascular Emergencies Part II (12-lead and QT)
d. Cardiac Monitor Setup and Lead Placement
e. ECG: 12-lead
2. Other online resources available for free:
a. Skillstat.com: basic ECG
b. PracticalClinicalSkills.com: basic ECG and 12-lead
**Critical Care needs to review ACLS algorithms and QT/QTc prolongation
Normal Cardiac Conduction Cycle and ECG Tracing
Pacemakers of the heart and inherent rates
• SA node
The main pacemaker of the heart
Inherent rate of 60-100 impulses per minute
When an impulse originates from this area, the rhythm is a “sinus” rhythm. The rate and
rhythm will determine what type of sinus rhythm it is.
• AV node (includes the area around the AV node called the Junctional area)
The 1st back up pacemaker of the heart (The Junctional area should take over if the SA node
fails)
Inherent rate of 40-60 impulses per minute
Rhythms that originate from this area called “Junctional” rhythms. The rate will determine
the type of Junctional rhythm.
• Purkinje Fibers
The last pacemaker of the heart (When the SA node and the Junctional area fail to fire, the
Purkinje fibers take over)
Rhythms that originate from this area are Ventricular rhythms
The last ditch effort of the heart to survive
Inherent Rate of 20-40 impulses per minute
,Characteristics of the ECG Tracing
• The P wave
Atrial Depolarization
When originating from the SA node, should be
Upright
Round
Smooth
PRI (PR Interval)
o 0.12-0.20 seconds (3-5 small boxes) in a normal rhythm
Time from the start of the atrial depolarization until the start of ventricular
depolarization
Measured from the very start of the P wave until the end of the isoelectric line.
If the PRI is greater than 0.2 the patient has some time of AV block.
The QRS complex
Ventricular Depolarization
When receiving an impulse from the AV node, should be
Narrow (< 0.12 seconds, or < 3 small boxes)
• The T wave
Ventricular Repolarization
Positive deflection after QRS complex (all leads except aVR and V1);
QT Interval
Measure from the start of the Q wave to the end of the T wave
QT interval is influenced by heart rate (the faster the heart rate, the shorter the QT interval)
Represents the electrical depolarization and repolarization of the ventricles
Lengthened QT interval increases risk of ventricular arrhythmias like Polymorphic
Ventricular Tachycardia (Torsades de Pointes)
Causes:
Medications (zofran, azithromycin, quinidine, Levaquin, etc.)
o Full list at: crediblemeds.org
Electrolyte imbalances (hypokalemia, hypocalcemia, hypomagnasemia)
Bradyarrhythmias
Hypothermia
Hereditary
QTc
QTc is the QT length corrected for the heart rate
Abnormal for males > 450 ms; for females > 470 ms
As QTc increases, the risk for ventricular arrhythmias increase
• The Isoelectric Line
The “baseline” of the telemetry strip (the flat line that runs across the strip when there is no
electrical activity). The isoelectric line follows the P wave prior to the QRScomplex
, QTc is the QT length corrected for the heart rate
Abnormal for males > 450 ms; for females > 470 ms
As QTc increases, the risk for ventricular arrhythmias increase
• The Isoelectric Line
The “baseline” of the telemetry strip (the flat line that runs across the strip when there is no
electrical activity). The isoelectric line follows the P wave prior to the QRScomplex
Characteristics of the ECG Paper
Horizontal Axis = Time
o Small boxes are 0.04 seconds each
o Large boxes are 0.20 seconds each (5 small boxes in 1 large box)
o 1500 small boxes in 1 minute
o 300 large boxes in 1 minute
Vertical Axis = Voltage
o Small box 1 mm
o Large box 5 mm
**Used when measuring ST elevation/depression and T wave voltage
Key Concepts
ECG tracing will only be as correct as the placement of the ECG electrodes
When the impulse originates from the SA node you will see a P wave that is Upright, Round,
and smooth resulting in a Sinus Rhythm
o When the Ventricles receive the impulse from the AV node you will see a normal,
narrow, QRS complex (< 0.12 seconds, < 3 small boxes)
The only exception will be when there is a Bundle Branch Block – Then the
QRS complex will be > 0.12 seconds.
When the impulse originates from the AV node you will see a P wave that is Inverted,
Absent or follows the QRS complex. These rhythms are Junctional Rhythms.
o An inverted P wave means the impulse is going the opposite direction through the
atria
, DYSRHYTHMIA REVIEW
1. MU modules/resources
a. A Journey to Understanding Dysrhythmias-A Self-Paced Course (Basic ECG)
b. Emergency Nursing Orientation 3.0: Cardiovascular Emergencies Part I
c. Emergency Nursing Orientation 3.0: Cardiovascular Emergencies Part II (12-lead and QT)
d. Cardiac Monitor Setup and Lead Placement
e. ECG: 12-lead
2. Other online resources available for free:
a. Skillstat.com: basic ECG
b. PracticalClinicalSkills.com: basic ECG and 12-lead
**Critical Care needs to review ACLS algorithms and QT/QTc prolongation
Normal Cardiac Conduction Cycle and ECG Tracing
Pacemakers of the heart and inherent rates
• SA node
The main pacemaker of the heart
Inherent rate of 60-100 impulses per minute
When an impulse originates from this area, the rhythm is a “sinus” rhythm. The rate and
rhythm will determine what type of sinus rhythm it is.
• AV node (includes the area around the AV node called the Junctional area)
The 1st back up pacemaker of the heart (The Junctional area should take over if the SA node
fails)
Inherent rate of 40-60 impulses per minute
Rhythms that originate from this area called “Junctional” rhythms. The rate will determine
the type of Junctional rhythm.
• Purkinje Fibers
The last pacemaker of the heart (When the SA node and the Junctional area fail to fire, the
Purkinje fibers take over)
Rhythms that originate from this area are Ventricular rhythms
The last ditch effort of the heart to survive
Inherent Rate of 20-40 impulses per minute
,Characteristics of the ECG Tracing
• The P wave
Atrial Depolarization
When originating from the SA node, should be
Upright
Round
Smooth
PRI (PR Interval)
o 0.12-0.20 seconds (3-5 small boxes) in a normal rhythm
Time from the start of the atrial depolarization until the start of ventricular
depolarization
Measured from the very start of the P wave until the end of the isoelectric line.
If the PRI is greater than 0.2 the patient has some time of AV block.
The QRS complex
Ventricular Depolarization
When receiving an impulse from the AV node, should be
Narrow (< 0.12 seconds, or < 3 small boxes)
• The T wave
Ventricular Repolarization
Positive deflection after QRS complex (all leads except aVR and V1);
QT Interval
Measure from the start of the Q wave to the end of the T wave
QT interval is influenced by heart rate (the faster the heart rate, the shorter the QT interval)
Represents the electrical depolarization and repolarization of the ventricles
Lengthened QT interval increases risk of ventricular arrhythmias like Polymorphic
Ventricular Tachycardia (Torsades de Pointes)
Causes:
Medications (zofran, azithromycin, quinidine, Levaquin, etc.)
o Full list at: crediblemeds.org
Electrolyte imbalances (hypokalemia, hypocalcemia, hypomagnasemia)
Bradyarrhythmias
Hypothermia
Hereditary
QTc
QTc is the QT length corrected for the heart rate
Abnormal for males > 450 ms; for females > 470 ms
As QTc increases, the risk for ventricular arrhythmias increase
• The Isoelectric Line
The “baseline” of the telemetry strip (the flat line that runs across the strip when there is no
electrical activity). The isoelectric line follows the P wave prior to the QRScomplex
, QTc is the QT length corrected for the heart rate
Abnormal for males > 450 ms; for females > 470 ms
As QTc increases, the risk for ventricular arrhythmias increase
• The Isoelectric Line
The “baseline” of the telemetry strip (the flat line that runs across the strip when there is no
electrical activity). The isoelectric line follows the P wave prior to the QRScomplex
Characteristics of the ECG Paper
Horizontal Axis = Time
o Small boxes are 0.04 seconds each
o Large boxes are 0.20 seconds each (5 small boxes in 1 large box)
o 1500 small boxes in 1 minute
o 300 large boxes in 1 minute
Vertical Axis = Voltage
o Small box 1 mm
o Large box 5 mm
**Used when measuring ST elevation/depression and T wave voltage
Key Concepts
ECG tracing will only be as correct as the placement of the ECG electrodes
When the impulse originates from the SA node you will see a P wave that is Upright, Round,
and smooth resulting in a Sinus Rhythm
o When the Ventricles receive the impulse from the AV node you will see a normal,
narrow, QRS complex (< 0.12 seconds, < 3 small boxes)
The only exception will be when there is a Bundle Branch Block – Then the
QRS complex will be > 0.12 seconds.
When the impulse originates from the AV node you will see a P wave that is Inverted,
Absent or follows the QRS complex. These rhythms are Junctional Rhythms.
o An inverted P wave means the impulse is going the opposite direction through the
atria
