Download SUPRAVENTRICULAR TACHYCARDIA

SUPRAVENTRICULAR
TACHYCARDIA
Garrett P. Clark, D.O.
SVT
• Can be divided into Atrial or AV
tachyarrhthmias.
• Are usually narrow-complex tachycardias
with regular, rapid rhythms - some
exceptions being A-fib & Multifocal Atrial
Tachycardias (MAT).
• Wide-complex tachycardia may occur when
aberrant conduction arises during SVT.
WIDE COMPLEX
TACHYCARDIA
SVT
• Episodic SVT that has a rapid onset &
termination is known as Paroxysmal
Supraventricular Tachycardia.
• Patients may present as totally asymptomatic or,
their symptoms could vary from minor
palpitations to chest pain and diaphoresis
mimicking heart attack.
• The most common presenting symptom in PSVT
is palpitation, occurring in greater than 96%.
SVT
• In a normally functioning heart, electric signal
from the SA node to the AV node causes the heart
to contract in two stages, thus pushing blood from
atria to ventricles and from ventricles to the body.
• One of the ways in which SVT can occur is when
the electrical impulse is sent back to the atria,
hence what we call “reentry.” Consequently, the
AV node’s next signal is early. This creates a
“continuous loop” which results in a rapid heart
rate.
SVT
Types of structural heart disease sometimes
associated with SVT:
• Hypertrophic cardiomyopathy
• Ebsteins Anomaly
• Other congenital heart diseases
SVT
Precipitating factors include:
• Increased caffeine
• EtOH
• Recreational drugs
• Hyperthyroidism
SVT
• Approximately 60% of SVT are due to
atrioventricular nodal reentry circuits.
• Approximately 30% of SVT are due to an AV
reentry circuit by a muscle bundle connecting the
atria and the ventricles directly. This is known as
an accessory pathway.
• Atrial tachycardias consist of approximately 10%
of the cases and are often focal in origin.
ATRIAL TACHYARRYTHMIAS
1)
2)
3)
4)
5)
6)
7)
Sinus Tachycardia
Inappropriate Sinus Tachycardia (IST)
Sinus Nodal Reentrant Tachycardia (SNRT)
Atrial Tachycardia
Multifocal Atrial Tachycardia (MAT)
Atrial Flutter
Atrial Fibrillation
AV TACHYARRHYTHMIAS
1)
2)
3)
4)
AV nodal reentrant tachycardia (AVNRT)
AV reentrant tachycardia (AVRT)
Junctional ectopic tachycardia (JET)
Nonparoxysmal Junctional Tachycardia
(NPJT)
Sinus Tachycardia
• HR faster than 100 bpm
• Physiologic acceleration of sinus rate
• Often in response to stressors such as: fever,
pain, anxiety, morning rounds,
hyperthyroidism, exercise, and stimulants
• Certain medications such as atropine
• Recreational drugs (coke, crack, etc..)
Sinus Tachycardia
Sinus Tachycardia
Inappropriate Sinus Tachycardia
• Accelerated sinus rate in absence of
physiologic stress.
• Most common in young women
• Mechanism is thought to be hypersensitivity
or abnormality of the SA node in the way it
responds to autonomic input.
Sinus Nodal Reentry Tachycardia
• Due to a reentry circuit which may be in or
close to the SA node
• Abrupt onset & offset
• HR usually between 100-150 bpm
• Usually a NORMAL p-wave morphology
Atrial Tachycardia
• Originates in the atrial myocardium
• May be caused by reentry or increased
automaticity
• Rate usually between 120-250 bpm
• P-wave morphology depends on site of
origin of the arrhythmia
• Sometimes due to digoxin toxicity
Atrial Tachycardia
Multifocal Atrial Tachycardia
• Arises within the atrial tissue
• May have 3 or more P-wave morphologies
• Usually occurring in elderly patients with
pulmonary disease
• EKG usually has irregular rhythm that may
be misconstrued as A-fib
MAT
MAT
Atrial Flutter
• Arises above the AV node
• Usually a macro-reentrant circuit within the
right atrium
• EKG findings: sawtooth P-waves in leads
II, III, aVF
• May be seen in patients with MI, Heart Dz,
EtoH, PE, cardiomyopathy, or myocarditis
A-Flutter
• Consider the diagnosis in patients with HR
of around 150.
• Atrial rate between 250-350 bpm
• A-flutter often presents with a 2:1 AV block
A-Flutter Treatment:
• Antiarrhythmic drugs like Ibutilide, flecainide,
propafenone (drugs that reduce the Vmax of
depolarization blocks Na+ inward current in
tissue with fast response action potentials).
• Rate control with Centrally acting CCB’s and BBlockers, or Digoxin
• Radiofrequency ablation is highly effective for
Long-term treatment
Atrial Flutter
Atrial Fibrillation
• Arises from chaotic depolarization of the
atria
• Atrial rate is usually between 300-600 bpm
• Ventricular rate may be >170 bpm
• A-fib occurring in young patients in the
absence of heart disease or other apparent
cause, is known as Lone (idiopathic) A-fib.
• EKG  ABSENCE OF P-WAVES !
A-FIB
A-FIB
A-FIB Causes:
•
•
•
•
•
•
•
P ulmonary Disease
I schemia
R heumatic Heart Disease
A nemia & Atrial Myxoma
T hyrotoxicosis
E thanol Heart
S epsis
•
•
•
•
HYPERTENSION
Heart Failure
CAD
Valvular Heart Disease
•
A-Fib
Treatment
If patient is unstable, proceed directly to bisphasic
cardioversion
• For rate control in a stable patient, you may use
centrally acting nondihydropyridine CCBs (diltiazem,
verapamil), or B-Blockers. In the case of reduced
ejection fraction, use of amiodarone or digoxin is
accepted.
• If A-fib is new and duration less than 48 hours,
anticoagulation is not necessary.
• If greater than 48 hours, anticoagulate with warfarin
for 3-4 weeks prior to cardioversion with an INR goal
of 2-3.
A-FIB
AV Tachyarrhythmias:
AV Nodal Reentrant Tachycardia
(AVNRT)
• The most common cause PSVT
• Diagnosed in up to 60% of patients with
narrow complex tachyarrhythmia
• Most common in women
• Reentry within the AV node
• P-waves are buried in the QRS complex
AVNRT
• The AV node is functionally divided into two
pathways that form the reentry circuit
• This differs from normal conduction where the AV
node has a single conduction pathway that conducts
to depolarize the bundle of His.
• In the 2 pathway phenomenon, there is a relatively
slow conduction pathway with a short refactory
period, while a second faster conducting pathway
exists with a longer refactory period. The coexistence
of these pathways paves the way for reentrant
tachycardia
AVNRT
SVT
An impulse from the
sinus node travels
through 2 pathways:
The AV Node
Connection and the
Accessory Pathway
SVT
Premature atrial
impulse reaches
an accessory
pathway in
refractory.
Conduction can
still occur in the
AV node.
SVT
The impulse reenters
the AV node as it
continues to
encounter
excitable tissue
and perpetuates
the circuit.
AV Reentrant Tachycardia (AVRT)
• This is the 2nd most common form of PSVT
• More common in males
• Associated with Ebstein anomaly (In Ebstein's
anomaly, one or two of the three leaflets are stuck to
the wall of the heart and don't move normally.)
• Is the result of two or more conduction pathways:
The AV node and one or more bypass tracts
AVRT
• The majority are conducted down the AV
node and then retrograde through the
“concealed” bypass tract.
• P waves are usually inverted and occur
shortly after the QRS.
AVRT
Junctional Ectopic Tachycardia
and Nonparoxysmal Junctional
Tachycardias
• These are rare forms of SVT that are alleged to
arise due to an increase in automaticity or
some type of triggered activity.
• Usually found to occur after valvular surgery,
Mi, or dig toxicity.
• EKG shows a regular, narrow QRS complex,
though P wave may not be visible
JET
• Junctional Ectopic Tachycardia (JET) is one of the most
common post-op tachyarrhythmias.
• The assumed mechanism is a small, abnormal automaticity
focus in the AV node or bundle of His.
• It most commonly presents immediately after the post-op
period, especially if the surgery involves the atrial or
ventricular septum.
• There are also congenital forms that present during the
newborn period and without provocation from surgery.
• There is AV dissociation, except for sinus capture beats
resulting from occasional antegrade conduction of a normal
sinus impulse.
• The next QRS complex occurs slightly earlier than expected.
JET
JET
Treatments
• Most SVTs count on the AV node to
maintain the reentry circuit.
• This can be interrupted by using vagal
maneuvers or medications that slow
conduction through the AV node.
Adenosine
• Randomized trials show that adenosine given at
6mg terminates SVT in 60 to 80%
• Up to 90 to 95% with 12mg
• However, Adenosine is CONTRAINDICATED in
patients who present with a wide QRS complex
unless SVT with aberrancy is certain.
• It is also contraindicated in heart-transplant
patients.
• In addition, Adenosine is not advised for use in
patients with severe COPD.
Adenosine Conversion
SVT Treatment
• SVT refractory to adenosine can be treated with
intravenous verapamil or a B-blocker.
• Other agents such as procainamide, or ibutilide
may be used as long as the patient’s BP is stable.
However, care must be taken in the consideration
of the possible bradycardic, hypotensive, and
proarrhythmic effects.
• Electric cardioversion is always a possible
alternative, but this is usually only considered in
patients who are hemodynamically stable after AV
nodal blocking agents have failed.
TREATMENTS
TREATMENTS
Beware of Wolf-Parkinson White
(WPW) Syndrome
• Patients with WPW syndrome have an
accessory pathway between the atria and the
ventricles due to a defect in the separation
between the atria and the ventricles during
fetal development.
• These patients are at risk for
tachyarrhythmias or sudden cardiac death.
• WPW is considered a subtype of AVRT
WPW Syndrome
• An accessory pathway allows antegrade conduction of
electrical impulses from the atria into the ventricles.
• This causes ventricular preexcitation with a short PR
interval and the classic delta wave - upstroke on the QRS,
best seen in lead V4
• Retrograde conduction from the ventricles will not show
the delta wave on a resting EKG.
• This is known as a “concealed bypass tract”.
• These patients are still prone to develop AVNRT.
• The treatment of choice is catheter ablation of the bypass
tracts
SVT with WPW Syndrome
• Unless the accessory pathway is proven to
have a long refractory period of 300msce or
greater, verapamil and digoxin are
contraindicated.
• These drugs increase the risk of rapid
ventricular response, leading to ventricular
fibrillation in patients with a-fib.
SVT with WPW Syndrome
• A-fib is the primary complication in WPW.
• If there is no evidence of a delta wave, or if the patient has
a concealed bypass tract, the standard treatments for
tachycardias are considered safe.
• If however, delta waves are present, Do Not Give AV
nodal blocking agents.
• This can allow for a 1:1 conduction of A-fib through the
bypass tract , leading to V-Fib and then cardiac arrest.
• Treatment of choice in these situations is procainamide or
cardioversion.
Delta Wave of WPW Syndrome
WPW Syndrome
Long Term Management of SVT
Short Term Management of SVT
SUMMARY
• The most common type of PSVT is AVNRT
• Atrial Tachycardia arises from an ectopic atrial
focus (i.e. increased automaticity)
• AVRT is reentry through an AV bypass tract
• AVNRT is reentry within the AV node
• If the QRS complex is narrow, think AVRT or
AVNRT
SUMMARY
• If the QRS complex is WIDE, think PSVT
with aberrancy or ventricular tachycardia
• If the QRS is wide and there are irregular,
bizarre QRS complexes, atrial fibrillation
conducting through an accessory pathway
may be occurring.
SUMMARY
• Termination of SVT can be accomplished
with carotid massage or administration of
adenosine.
• Medical management can be accomplished
using AV blocking drugs like CCBs or Bblockers
• Curative therapy consists of catheter-based
ablation.
Reedy Fur Dee Questions?
1) All of the following are
considered AV Tachyarrhythmias
EXCEPT:
A)
B)
C)
D)
E)
AVNRT
AVRT
Junctional Ectopic Tachycardia
Multifocal Atrial Tachycardia
Nonparoxysmal Junctional Tachycardia
2) The most common cause of PSVT
is:
A)
B)
C)
D)
E)
AVNRT
AVRT
MAT
JET
BOBAFETT
3) A-Fib that occurs in younger people
without heart disease or other apparent cause
is known as:
A) JET
B) MAT
C) Lone
D) Prone
E) Groan
References:
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htpp://www.introvexia.com/archives/2004_09.html
http://connection.lww.com/Products/morton/Ch17.asp
http://pedsccm.wustl.edu/all-net/english/cardpage/electric/CVsurg/dysrh-3.htm
www.grundkurs-ekg.de/ekgloesungen/l_beispiele/l_ekg13_wpwsyndrom.gif
http://www.txai.org/edu/irregular/junctional.htm
www.emedu.org/ecg/images/ans/2avnrt_1.jpg
www.emedu.org/ecg/voz.php
http://www.emedicine.com/med/topic1762.htm
Le, Tao, et al. First Aid For The Internal Medicine Boards. New York:
McGraw-Hill, 2006
Delacretaz, Etienne, M.D. “Supraventricular Tachycardia.” The New England
Journal of Medicine 9 Mar. 2006: 1039-1051.