supraventricular tachycardia garrett p. clark, d.o

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) Sinus Tachycardia

2) Inappropriate Sinus Tachycardia (IST)

3) Sinus Nodal Reentrant Tachycardia (SNRT)

4) Atrial Tachycardia

5) Multifocal Atrial Tachycardia (MAT)

6) Atrial Flutter

7) Atrial Fibrillation

AV TACHYARRHYTHMIAS

1) AV nodal reentrant tachycardia (AVNRT)

2) AV reentrant tachycardia (AVRT)

3) Junctional ectopic tachycardia (JET)

4) 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 B-Blockers, 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 Tachycardiaand 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 B-blockers

• Curative therapy consists of catheter-based ablation.

Reedy Fur Dee Questions?

1) All of the following are considered AV

Tachyarrhythmias EXCEPT:

A) AVNRT

B) AVRT

C) Junctional Ectopic Tachycardia

D) Multifocal Atrial Tachycardia

E) Nonparoxysmal Junctional Tachycardia

2) The most common cause of PSVT is:

A) AVNRT

B) AVRT

C) MAT

D) JET

E) 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:

• 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.