Practice Alert
Dysrhythmia Monitoring
Authors & Reviewers:
Nancy M. Richards, RN, CNS, MSN, CCRN, CCNS
Issued April 2008
Lecture Content
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Skin Preparation
Lead Placement
Ventricular Dysrhythmias
QT Intervals
Practice Alert - Dysrhythmia Monitoring
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Skin Preparation
Skin oil and debris can cause noisy
signals
Clip excessive hair before placing
electrodes
Clean skin with alcohol or washcloth
to remove skin oils and/or debris
Practice Alert - Dysrhythmia Monitoring
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Electrode Placement
Limb leads (I,II,III)
Place to decrease muscle artifact during limb
movement
Placement
Right Arm (RA) infra-clavicular fossa close to right
shoulder
Left Arm (LA) infra-clavicular fossa close to left
shoulder
Left Leg (LL) below rib cage on left side of
abdomen
Ground (RL) anywhere on torso
Practice Alert - Dysrhythmia Monitoring
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Electrode Placement
Precordial Leads
Dependent on patient’s needs and goals of
monitoring
Consider marking electrode location with
indelible ink
 Ensures electrodes will be placed in same
position.
Precordial leads misplaced by 1 ICS can
change the QRS morphology
Practice Alert - Dysrhythmia Monitoring
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Dysrhythmia Monitoring
Lead V1 to distinguish Ventricular
Tachycardia (VT) from Supraventricular
Tachycardia (SVT) with aberrant
conduction
V1 lead of choice for dysrhythmia
monitoring
Lead II or III if patient condition indicates
need to monitor for atrial dysrhythmias
Practice Alert - Dysrhythmia Monitoring
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Dysrhythmia Monitoring
Lead Placement
V1 (5 lead system)
 4th intercostal space (ICS) to the
right of the sternum
MCL1 (3 lead system)
4th intercostal space (ICS) to the
right of the sternum
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3 Lead Electrode Placement
Simple 3electrode lead
system
Electrode
placement for
MCL1
Only 1 lead can
be monitored
with a 3 lead
system
Practice Alert - Dysrhythmia Monitoring
From Philips Cardiac
Monitoring Pocket Card 2002
8
5 Lead Electrode Placement
Angle of
Louis
5 lead systems allow for
the recording of any of
the six limb leads plus
one precordial (V) lead.
Shown lead placement for
recording V1 or V6.
V1
V
6
Practice Alert - Dysrhythmia Monitoring
5 Lead monitoring
systems are
recommended over 3
lead systems for
monitoring QRS
morphology
From Philips Cardiac
Monitoring Pocket Card 2002
9
QRS Morphology
Ventricular Tachycardia
 V 1 or MCL1
 Monophasic R wave
 Notched R wave with
taller left peak
 Biphasic RS
 Biphasic qR
 Any of the following in V1
or V2
 V6 or MCL6
 Biphasic rS with R:S
ratio <1.0
 Monophasic Q
 Notched QS
 Biphasic qR
 Intrinsicoid deflection >
70ms
 R > 30ms
 Slurred or notched S
descent
 QRS onset to S nadir
>60 ms
Practice Alert - Dysrhythmia Monitoring
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QRS Morphology
Practice Alert - Dysrhythmia Monitoring
From Philips Cardiac
Monitoring Pocket Card 2002
11
QRS Morphology
SVT with Aberration
V1 or MCL1
Bimodal rR’ or
triphasic rsR’
All of the following in
V1 or V2
V6 or MCL6
Triphasic qRs with
R:s ratio > 1.0
Intrinsicoid
deflection < 50 ms
 R < 30 ms or no R
 Straight S descent
 QRS onset to S nadir
< 60 ms and no Q in
V6
Practice Alert - Dysrhythmia Monitoring
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QRS Morphology
Practice Alert - Dysrhythmia Monitoring
From Philips Cardiac
Monitoring Pocket Card 2002
13
QRS Morphology
Not Helpful
V1 or MCL1
R slurred or notched
with taller right peak
V6 or MCL6
Monophasic R
Notched R with taller
left or right peak
Biphasic Rs with R:S
ratio > 1.0
Applies only to tachycardias with a positive waveform in V1
Practice Alert - Dysrhythmia Monitoring
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QRS Morphology
Practice Alert - Dysrhythmia Monitoring
From Philips Cardiac
Monitoring Pocket Card 2002
15
Accurate Lead Placement
V1
V1
II
I
I
(A) Onset of wide QRS complex
tachycardia shows a “taller right peak”
pattern in lead V1, which is unhelpful in
distinguishing between ventricular
tachycardia and supraventricular
tachycardia with aberrant conduction.
Examination of the patient revealed that
the V1 electrode was misplaced to the
5th, rather than the 4th intercostal
space
Practice Alert - Dysrhythmia Monitoring
(B) After lead placement was
corrected, another episode of wide
QRS complex tachycardia showed the
“taller left peak” pattern in lead V1
which is strongly suggestive of
ventricular tachycardia (Wellens, et al
1978). Subsequent invasive cardiac
electrophysiologic study confirmed the
patient had ventricular tachycardia.
Used with permission of
Barbara J. Drew RN, PhD
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QT Interval
Approximate measure of the duration
of ventricular repolarization.
Measured from the beginning of the Q
wave to the end of the T wave
Varies with heart rate
Lengthens with bradycardia
Shortens with tachycardia
Practice Alert - Dysrhythmia Monitoring
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QT Interval
Measure from beginning
of the QRS complex to
the end of the T wave
Practice Alert - Dysrhythmia Monitoring
From Philips Cardiac
Monitoring Pocket Card 2002
18
QTc Interval
QT interval corrected for heart rate (QTc)
Formula for calculating QTc (Bazett’s formula)
QTc > 0.50 seconds considered
dangerously prolonged and is associated
with a higher risk of Torsades de Pointes.
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Measuring the QTc
R – R = 0.72
QT = 0.36
• Measure the QT of the second complex used in R – R measurement.
• Using Bazett’s formula: QTc = 0.36 / √0.72 = 0.36 / 0.85 = 0.42
QTc = 0.42
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Torsades de Pointes
Polymorphic Ventricular Tachycardia
Precipitated by prolonged QT interval
Not responsive to and may be
exacerbated by class Ia and some Ic
medications
Practice Alert - Dysrhythmia Monitoring
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Pause
Arrhythmias associated with prolonged QT interval that
place the patient at immediate risk for developing torsades
de pointes. ECG characteristics include underlying
prolonged QT interval, T wave alternans, polymorphic
ventricular premature beats that fall near the T-U portion of
repolarization, pause-dependent enhancement of the QT
interval (arrow), and non-sustained polymorphic
ventricular tachycardia.
Practice Alert - Dysrhythmia Monitoring
Used with permission of
Barbara J. Drew RN,
PhD
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Torsades de Pointes
Monitor QT interval for patients identified at
high risk:
Patients on medications known to prolong QT
interval
Quinidine, procainaminde,
disopyraminde, sotalol, dofetilide, ibutilide
For more information see:
http://www.arizonacert.org/medical-pros/drug-lists/printabledrug-list.cfm
Patients who overdose on potentially prodysrhythmic medications
New onset bradycardia
Severe hypokalemia or hypomagnesemia
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Treatment
Emergency
• IV Magnesium
• Defibrillation
• Overdrive
pacing
Practice Alert - Dysrhythmia Monitoring
Long Term
• Monitor QTc
interval
• Discontinue or
modify drug dose
if QTc interval
increases > 0.50
secs
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Need Further Assistance?
For more information or further
assistance, please contact a
clinical practice specialist with the
AACN Practice Resource Network.
Email:
practice@aacn.org
Phone:
(800) 394-5995
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