Student ECG Cardiac Rhythms

Student ECG
Cardiac Rhythms
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SUPRAVENTRICULAR
RHYTHMS
Rhythms originating in the
sinus node, atria, or AV node
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Rhythms Contents
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SUPRAVENTRICULAR
VENTRICULAR
Normal Sinus Rhythm 6
Idioventricular Rhythm 48
Sinus Tachycardia 7
Accelerated Idioventricular Rhythm 50
Sinus Bradycardia 7
Ventricular Tachycardia 52
Sinus Arrhythmia 8
Ectopic Atrial Rhythm 10
Wandering Atrial Pacemaker 13
Multifocal Atrial Tachycardia 16
Torsades de Pointes 56
Ventricular Fibrillation 61
Asystole 63
PVCs 64
Pacemaker Rhythms 67
Atrial Flutter 18
Atrial Fibrillation 23
SVT(AVNRT) 29
Junctional Rhythm 36
Wolf Parkinson White 40
PACs 45
3
Sinus Node Rhythms
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Normal Sinus Rhythm
Normal sinus rhythm is the normal heart
rhythm characterized by p waves emanating
from the sinus node, upright in II, III, and aVF,
and at a rate from 60 to 100.
Under normal circumstances there is slight
irregularity due to autonomic fluctuation with
respiration. Loss of this variability could
signify autonomic dysfunction.
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Sinus Tachyardia and
Bradycardia
Sinus tachycardia is defined as a sinus rhythm at a
rate greater than 100. It can get as high as 200
bpm with exercise, but otherwise rarely exceeds
150 bpm. Causes are numerous; treatment is
aimed at the underlying cause.
Sinus bradycardia is a sinus rhythm at a rate less
than 60. It may be physiologic, such as during
sleep, with highly trained athletes, from numerous
medications. In general treatment may be
necessary if the heart rate while awake is < 40 or if
>40 and the patient has symptoms
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Sinus Arrhythmia
Normally the heart rate accelerates with
inspiration and slows with expiration due to
autonomic fluctuation.
If the irregularity is exaggerated, it is called
sinus arrhythmia.
In sinus arrhythmia, the P waves are normal, but
the rhythm is regularly irregular--this is not
uncommon in children and occ. adults.
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Atrial Rhythms
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Ectopic Atrial Rhythm
The focus of depolarization is somewhere in
the atrium, not the sinus node. Therefore the
p-wave axis is usually abnormal.
On the ECG, P waves are often inverted in II,
III, and aVF, where they are normally upright,
yet they are constant and regular.
The PR interval may be short as the focus is
often close to the AV node.
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Ectopic Atrial Rhythm
P waves are inverted in II, III, aVF, but the PR interval is constant and the rhythm is regular
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Ectopic Atrial Rhythm
Cause: Usually increased automaticity in the
atria (Increased spontaneous depolarization).
Symptoms: none usually
Treatment: none
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Wandering Atrial Pacemaker
In wandering atrial pacemaker, there are differing foci of
depolarization in the atrium other than the sinus node.
On the ECG the P waves will be of varying
morphologies: some pointed, double peaked, inverted,
etc.
There should be at least 3 different morphologies
apparent.
Because of differing distances from the AV node, the
P-R intervals will also vary.
The rhythm is irregular with a rate less than 100.
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Wandering Atrial Pacemaker
Note differing P waves; rhythm is irregular but rate is less than 100.
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Wandering Atrial Pacemaker
Cause: usually occurs in patients with sinus
node dysfunction, atrial abnormalities,
increased vagal tone to the SA node, and in
normals during sleep.
Symptoms: may notice irregular heartbeat,
but usually none.
Treatment: none; may be transient.
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Multifocal Atrial Tachycardia
MAT is similar to wandering atrial pacemaker,
except the rate is above 100 bpm.
Sometimes the atrial depolarizations will come
early and be blocked due to the refractory period
of the AV node. They may also be buried in the
prior T wave, causing changes in its morphology.
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Multifocal Atrial Tachycardia
Different P Wave morphologies
Very early P wave hidden in T wave
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Multifocal Atrial Tachycardia
MAT is most often seen in patients with severe
pulmonary disease (COPD), CHF, especially during
exacerbations.
Treatment: treat underlying disorder.
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Atrial Flutter
This is usually a reentrant type of arrhythmia
that occurs in the atria.
Instead of discreet p waves, flutter or “F” waves
are seen, typically at a rate close to 300.
They are best seen in leads II, III, aVF, and they
are conducted to the ventricles at a slower rate
due to the longer refractory period of the AV
node.
Typical conduction is 2:1, 3:1, 4:1, etc. The flutter
waves are usually sharp and “saw-toothed.”
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Atrial Flutter
Saw-toothed flutter waves, best seen in lead II or III
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What is the rhythm?
Same patient:
Always look at leads II, III and aVF to see P waves more
clearly.
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2 to 1 Atrial Flutter
Atrial Rate = 300; Ventricular Rate=150(initially)
fffff ff
The rhythm starts out with a 2:1 atrial flutter, then the ratio
changes. Every other flutter wave is buried in a QRS.
Atrial flutter may be regular or irregular.
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Atrial Flutter
Symptoms: if ventricular rate fast, may have
dyspnea, angina, etc.
Treatment: usually AV blocking meds to
control ventricular rate if fast, then
cardioversion either electrically or by
medications.
Arrhythmia focus can be ablated by EP
cardiologist.
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Atrial Fibrillation
This rhythm results from chaotic random
depolarization of the atria.
The most common associations are with
ischemic, rheumatic, hypertensive heart
disease, thyrotoxicosis, heart failure, and
aging.
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Atrial Fibrillation
Chaotic, uncoordinated atrial activity on ECG
Atrial fibrillation may be coarse, with very
visible chaotic atrial activity, or fine, even to
the point of almost no baseline activity.
The ventricular conduction may be fast or
slow, but shows an irregularly irregular
pattern.
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Atrial Fibrillation
From coarse(A) to fine(C)
QRS
complexes
QRS
complexes
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Fine Atrial Fibrillation
Look closely; sometimes atrial fibrillation is very fine and can be
confused with a junctional rhythm.
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Atrial Fibrillation
Symptoms: like atrial flutter if ventricular rate
fast. Increased risk of stroke, depending on
age, htn, etc.
Treatment: rate control, anticoagulation vs
conversion to sinus electrically or via
medications.
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AV Nodal Rhythms
Supraventricular Tachycardia (AVNRT)
Junctional Rhythm
Accelerated Junctional Rhythm
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Supraventricular Tachycardia
(SVT)
Most are AV nodal reentrant tachycardias (AVNRT),
occurring in or around the AV node.
Mechanism: when a PAC hits the AV node at the
right moment, it can initiate a re-entrant circuit
resulting in AVNRT.
Usually conduction proceeds down a fast
pathway and back up a slow pathway, which has a
unidirectional block of antegrade impulses that is
variably present.
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AVNRT Mechanism
1. Atrial Impulse
2. PAC enters
3. Re-entry
(PAC)
Fast pathway then
recovers
and conducts
retrograde
AV Node
(final common pathway)
Slow Pathway
blocked
Slow pathway
recovers first; fast
still refractory
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AVNRT
Less frequently conduction proceeds in the
reverse order
Reentrant circuits can occur with pathways
outside the AV node.
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SVT (AVNRT)
ECG manifestations:
Narrow complex regular tachycardia
usually > 160 bpm but can be 120-220
P waves may:
Be absent (most)
Just follow the QRS-often inverted
Just precede the QRS(unusual)
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SVT (AVNRT)
Carotid Massage
“Usual” AVNRT with a rapid, narrow complex QRS
and no discernable P waves. Conversion to NSR
occurs with carotid massage.
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SVT (AVNRT)
Notice the small impulse just after the QRS, which is a retrograde P wave
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SVT- Treatment
Symtoms: palpitations, dyspnea, angina
Acute treatment is with vagal maneuvers like
carotid massage or valsalva
Drug therapy-adenosine, verapamil, beta
blockers, sometimes other antiarrhythmics
AV nodal ablation is definitive therapy and
may be the therapy of choice as meds are
only modestly effective.
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Junctional Rhythm
AV nodal tissue can take over as the
pacemaker of the heart, especially in the
event of sinus node dysfunction.
A junctional rhythm is regular, and usually
no p waves will be seen. They may be:
buried in the QRS complex,
occur afterwards during the ST segment, or be
superimposed on the T waves.
just precede the QRS (rare).
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Junctional Rhythm
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Junctional Rhythm
The QRS width is narrow as conduction proceeds
normally down the bundle branches, and the rate
is approx. 40-60.
At higher rates, it is referred to as an accelerated
junctional rhythm. When the rate is about 120 or
greater, it is probably SVT.
Junctional rhythm is not re-entry like AVNRT, but is
due to failure of the SA node or increased
automaticity (accelerated junctional rhythm).
Treatment: atropine for JR if HR inadequate.
Usually no treatment for accelerated JR.
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Miscellaneous
Supraventricular
Rhythms
Wolf Parkinson White
PACs
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Wolf-Parkinson-White
In WPW there is an accessory bypass tract that
directly connects the atrium to the ventricle.
It is known as the bundle of Kent, and
conducts without the delay seen in the AV
node. This is know as pre-excitation.
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WPW
The ECG manifestations are as follows:
1. Short PR interval
2. Delta wave (early abnormal ventricular
depolarization).
3. Widened QRS (due to the delta wave).
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WPW
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WPW
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WPW
Patients are prone to supraventricular arrhythmias
that can conduct rapidly down the accessory
pathway at very fast rates leading to ventricular
fibrillation and death. This, however, occurs rarely.
Definitive treatment is ablation of the accessory
pathway.
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PACs
Common extra beats where the atrium
depolarizes spontaneously before the next
sinus beat should appear.
They often have premature and abnormal
looking P waves
The QRS usually looks like the other QRS
complexes.
The following R-R interval is usually the
same as the sinus beats (or close).
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PACs
Notice the early impulse with the unusual P wave that
precedes the QRS.
The P wave will be buried in the T wave if the beat comes
very early.
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VENTRICULAR
ARRHYTHMIAS
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Idioventricular Rhythm
A focus in the ventricle takes over as the
pacemaker of the heart This may be due to
failure of pacemaker function from the SA
node and AV node.
On the ECG there are wide, bizarre QRS
complexes at a rate of 20-40, often
associated with t-wave inversions. If this
rhythm is seen in with a heart block, it is
know as a ventricular escape rhythm.
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Idioventricular Rhythm
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Accelerated Idioventricular
Rhythm (AIVR)
Accelerated idioventricular rhythm (AIVR) is a
variant of idioventricular rhythm with a rate of
60-100, and often occurs in short bursts after
an MI or may be seen with digoxin toxicity. It
is from increased automaticity.
AIVR is usually transient and benign, and does
not carry the same prognosis as ventricular
tachycardia. It usually does not require
treatment.
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AIVR in a patient
2 days post MI
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Ventricular Tachycardia
A potentially dangerous rhythm that is often
a re-entrant ventricular arrhythmia, arising
from a site of abnormal ventricular tissue,
often due to ischemia, fibrosis,
cardiomyopathy, etc.
It also can be precipitated by hypo or
hyperkalemia, severe hypocalcemia,
hypomagnesemia, severe illness with high
catecholamine states, and congenital causes.
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Ventricular Tachycardia
ECG findings:
Rapid, wide, bizarre looking QRS complexes at
a rate usually above 120-140.
The rhythm may be regular or irregular.
Sometimes p-waves that are unrelated to the
QRS complexes are seen (AV dissociation),
usually confirming the diagnosis of v-tach.
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Ventricular Tachycardia
Here, a PVC landing on T wave initiates V Tach
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Ventricular Tachycardia
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Ventricular Tachycardia
Treatment:
If stable, D/C cardioversion, IV amiodarone,
occasionally lidocaine.
If unstable (severe dyspnea, chest pain,
hypotension)-defibrillation.
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Torsades de Pointes
(Twisting of the Points)
This is a form of polymorphic ventricular
tachycardia that is caused from prolongation of
the QT interval (many drugs, low Mg, etc.).
On the ECG it looks like v-tach, but the axis shifts
180 degrees, so the complexes shift from positive
to negative over several beats.
Treatment is with IV magnesium, or pacing to
shorten the QT interval.
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Torsades de Pointes
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Torsades de Pointes
The Axis shifts 180 degrees
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Torsades de Pointes
Treatment:
IV Magnesium 2g bolus
Defibrillation if sustained/unstable
Pacing, isoproterenol to increase HR and
shorten QT.
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Ventricular Fibrillation
This is a lethal rhythm resulting from
chaotic,random depolarization of the
ventricle.
It is the usual cause of sudden death.
There is an undulating, disorganized rhythm
without distinct QRS complexes on the ECG,
which may be coarse or fine.
Treatment is immediate electrical
defibrillation.
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Ventricular Fibrillation
Coarse
Fine
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Asystole
No visible electrical actvity
“Flatline” ECG
Need to be sure it is not fine v-fib.
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PVCs
Premature ventricular contractions are very
common, and may be found in up to 40% of
normal individuals.
Their prognostic importance depends on the
underlying condition and presence of
structural heart disease.
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PVCs
On the ECG they appear as early, wide, bizarrelooking complexes with a different morphology
than the underlying rhythm. They typically have an
abnormal repolarization pattern, often with ST
segment depression and T wave inversion.
Ventricular bigeminy refers to the pattern of every
other beat being a PVC; trigeminy is where every
third beat is a PVC. PVCs grouped in 2s are referred
to as couplets.
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PVCs
Note the compensatory pause that occurs because the next
cycle comes during the PVC or when the ventricle is refractory.
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Pacemaker-Ventricular
The ventricular lead is in the right ventricle, and the
resultant complex is wide, often with T wave inversions.
Notice the spikes just preceding the QRS.
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Dual Chamber Pacemaker
(a)
(v)
Note both atrial(a) and ventricular(v) pacing occur,
depending on the need.
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Dual Chamber Pacemaker
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Supraventricular Arrhythmia
Algorithm
(use for narrow complex QRS).
Is Rhythm Regular
Or Irregular?
Regular
Irregular
P Waves
Present
HR<100
P Waves Absent
(Occasionally
follow or
precede QRS)
HR>100
Flutter Waves
Inverted in
II, III, aVF
Upright in
II, III, aVF
Atrial Flutter
Ectopic Atrial
Rhythm or
Occasional
Junctional
Normal Sinus/
Sinus Brady
Sinus Tachycardia
Atrial Tachycardia
(P waves may be
inverted)
Flutter Waves
Atrial Flutter
P Waves Present
HR 40-60
HR 80-100
HR>120
Junctional
Rhythm
Accelerated
Junctional
SVT(us AVNRT)
HR<100
P Waves Absent
or indiscernable
HR>100
P Wave
morphology
constant
P wave
morphology
changes
Flutter Waves
Present
Sinus
dysrhythmia
Wandering
Atrial Pacemaker,
NSR with PACs
Atrial Flutter
MAT,
Sinus Tach with
PACs or
PVCs
Atrial Fibrillation
Flutter Waves
Present
Atrial Flutter
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Ventricular Arrhythmia
Algorithm
(Use for Wide Complex QRS)
Look at
Relationship
b/t P Waves
and QRS
P Waves
Absent
or unrelated to QRS
HR <100
Idioventricular
(HR 20-40);
AIVR if
HR 60-100
Complete Heart
Block- consider
if more P's
than QRS
P Waves
Present
Before QRS
HR >100-120
Ventricular
Tachycardia
Supraventricular
Rhythm
with Aberrancy
(BBB, etc)
Ventricular
Fibrillation
(Chaotic
depolarization)
Think Torsades
if Axis is
Shifting 180
Degrees
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