Practice Alert Dysrhythmia Monitoring Issued April 2008 Authors & Reviewers: Nancy M. Richards, RN, CNS, MSN, CCRN, CCNS

Practice AlertPractice AlertDysrhythmia MonitoringDysrhythmia Monitoring

Issued April 2008Issued April 2008

Authors & Reviewers:Authors & Reviewers:Nancy M. Richards, RN, CNS, MSN, CCRN, CCNSNancy M. Richards, RN, CNS, MSN, CCRN, CCNS

Practice Alert - Dysrhythmia Monitoring2

Lecture Content

Skin Preparation Lead Placement Ventricular Dysrhythmias QT Intervals


Skin Preparation

Skin oil and debris can cause noisy signals Clip excessive hair before placing

electrodesClean skin with alcohol or washcloth

to remove skin oils and/or debris


Electrode PlacementLimb leads (I,II,III)

Place to decrease muscle artifact during limb movement

PlacementRight Arm (RA) infra-clavicular fossa close to right

shoulderLeft Arm (LA) infra-clavicular fossa close to left

shoulderLeft Leg (LL) below rib cage on left side of

abdomenGround (RL) anywhere on torso


Electrode Placement

Precordial LeadsDependent on patient’s needs and goals of

monitoringConsider 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


Dysrhythmia Monitoring

Lead V1 to distinguish Ventricular Tachycardia (VT) from Supraventricular Tachycardia (SVT) with aberrant conduction

V1 lead of choice for dysrhythmia monitoringLead II or III if patient condition indicates

need to monitor for atrial dysrhythmias


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


3 Lead Electrode Placement

Simple 3-electrode lead system

Electrode placement for MCL1

Only 1 lead can be monitored with a 3 lead system

From Philips Cardiac Monitoring Pocket Card 2002


5 Lead Electrode Placement

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.

5 Lead monitoring systems are recommended over 3 lead systems for monitoring QRS morphology


V1V1

V

6

V

6

Angle of Louis

Angle of Louis


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

R > 30ms Slurred or notched S

descent QRS onset to S nadir

>60 ms

V6 or MCL6 Biphasic rS with R:S

ratio <1.0 Monophasic Q Notched QS Biphasic qR Intrinsicoid deflection >

70ms


QRS Morphology



QRS MorphologySVT with Aberration

V1 or MCL1

Bimodal rR’ or triphasic rsR’

All of the following in V1 or V2 R < 30 ms or no R Straight S descent QRS onset to S nadir

< 60 ms and no Q in V6

V6 or MCL6

Triphasic qRs with R:s ratio > 1.0

Intrinsicoid deflection < 50 ms


QRS Morphology



QRS MorphologyNot Helpful

V1 or MCL1

R slurred or notched with taller right peak

V6 or MCL6

Monophasic RNotched R with taller

left or right peakBiphasic Rs with R:S

ratio > 1.0

Applies only to tachycardias with a positive waveform in V1


QRS Morphology



Accurate Lead Placement

V1

II

V1

II

(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

(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


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 rateLengthens with bradycardiaShortens with tachycardia


QT Interval

Measure from beginning of the QRS complex to the end of the T wave



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.


Measuring the QTc

• 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

QT = 0.36

R – R = 0.72


Torsades de Pointes

Polymorphic Ventricular TachycardiaPrecipitated by prolonged QT intervalNot responsive to and may be

exacerbated by class Ia and some Ic medications


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.

Pause

Used with permission of Barbara J. Drew RN, PhD


Torsades de PointesMonitor QT interval for patients identified at

high risk:Patients on medications known to prolong QT

intervalQuinidine, procainaminde,

disopyraminde, sotalol, dofetilide, ibutilideFor more information see:

http://www.arizonacert.org/medical-pros/drug-lists/printable-drug-list.cfm

Patients who overdose on potentially pro- dysrhythmic medications

New onset bradycardiaSevere hypokalemia or hypomagnesemia


Treatment

Emergency•IV Magnesium•Defibrillation•Overdrive pacing

Long Term•Monitor QTc interval•Discontinue or modify drug dose if QTc interval increases > 0.50 secs


For more information or further assistance, please contact a clinical practice specialist with the AACN Practice Resource Network.

Email:[email protected]

Phone:

(800) 394-5995

Need Further Assistance?

Documents

Practice Alert Dysrhythmia Monitoring Issued April 2008 Authors & Reviewers: Nancy M. Richards, RN, CNS, MSN, CCRN, CCNS