APPROACH TO NARROW QRS COMPLEX TACHYCARDIA

Dr Dharam Prakash Saran

STEP wise• Look for QRS duration.

• QRS complex regular/irregular.

• Then look for presence of p waves.

• P waves morphology

• P waves and QRS relationship 1:1

• AV block present.

• Termination initiation of tachycardia.

• Effect of BBB on tachycardia cycle length.

In brief from the diagram clues

• Response to carotid sinus massage or adenosine –with termination of arrhythmia with Pwave –AVNRT

• Tachycardia persists with AV block –AT,AFL,SANRT

• Pseudo r ‘ wave in V1 –AVNRT

• SHORT RP interval – AVNRT,AVRT

• Long RP interval – AT,SANRT,AVNRT atypical

NARROW COMPLEX QRS TACHYCARDIA

SHORT RP INTERVAL

TYPICAL AVNRT

AVRT

LONG RP INTERVAL

ATYPICAL AVNRT

AVRT slow retrograde conduction

Permanent Form junctional

tachycardia

ATRIAL TACHYCARDIA

SANRT

INAPPROPRIATE ST

ECG findings

Pwaves

no

Irregular

R-R interval

ATRIAL FIBRILLATION

Regular

R-R interval

AVNRT

yes

NORMAL MORPHOLOGY

SINUS TACHYCARDIA

SINUS NODE REENTRY

INAPPROPRIATE SINUS TACHYCARDIA

Differentiation of AVNRT from AVRT

P wave present but not of same

morphology as sinus rhythm

Pseudo r’ wave in

V1

AVNRT

Pseudo S wave on lead II

AVNRT

Pwave

ST-T changes

Positive in lead I

AVRT

Right posteroseptal

Accessory pathway

Negative in lead I

AVRT

Left sided accessory pathway

AVNRT

• Presence of a narrow complex tachycardia with regular R-R

intervals and no visible p waves.

• P waves are retrograde and are inverted in leads II,III,AVF.

• P waves are buried in the QRS complexes –simultaneous

activation of atria and ventricles – most common presentation

of AVNRT –66%.

• If not synchronous –pseudo s wave in inferior leads ,pseudo r’

wave in lead V1---30% cases .

• P wave may be farther away from QRS complex distorting the

ST segment ---AVNRT ,mostly AVRT.

AV NODAL REENTRANT TACHYCARDIA

AVRT• Typical – RP interval < PR interval

• RP interval > 80 milli sec

• Atypical –RP interval > PR interval

• Concealed bypass tract – only retrograde conduction

• Manifest bypass tract– both anterograde and retrograde.

• Electrical alternans –the amplitude of QRS complexes varies by 5 mm alternatively.

• Rate related BBB occuring and the rate of tachycardia is decreasing –then the bypass tract is on the same side of the block.

AV REENTRANT TACHYCARDIA

WPW syndrome

• Two types

• Orthodromic

• Antidromic

• Antidromic is wide complex tachycardia

• In NSR detected by delta wave.

• Can ppt into AF and VF on use of AV nodal blockers

• MEMBRANE ACTIVE ANTIARRHTYHMIC DRUGS are safe.

• CONCEALED WPW syndrome – no delta wave .less risk of AF

Focal Atrial Tachycardia

• P wave morphology changes.• PR interval > 0.12 sec .• Second,third degree AV block can occur.• Tachycardia terminates with a qrs complex ..• Right atrial origin– p wave inverted in V1.• Upright in lead AVL • Opposite if of left atrial origin• Superior origin –upright p waves in inferior leads• Inferior origin –p waves are inverted in inferior

leads.

Multifocal Atrial Tachycardia• At least three consequtive p waves with different

morphologies with a rate > 100 bpm to be present.

• Isoelectric baseline between p waves.

• Also called as choatic atrial tachycardia

• Mostly seen in COPD ,electrolyte abn,theophylline

• Rate usually does not exceed 130-140 bpm.

Multifocal Atrial Tachycardia

SANRT

• Microreentrant tachycardia

• Usually precipitated and terminated by

premature atrial complexes.

• Atrial rate is usually 120-150 bpm.

• AV block can occur.

Junctional tachycardias

• Non paroxysmal – accelerated junctional rhythm• Rate < 100 bpm Usually junctional node 40-60 bpm• Paroxysmal or focal junctional tachycardia is rare –

automaticity.• 110-250bpm.• P waves may be before or after QRS complex• Infrequent and nonsustained episodes –no treatment• Acute termination of SVT establish the mechanism of SVT in

case of acute setting.• Long term goal is abolishing the arryhthmia substrate.• Precipitating factors – electrolyte

imbalance,hypoxia,ischemia,hyperthyroidism to be sought out.

TREATMENT OF SVT

• A 12 lead ECG during tachycardia and NSR.

• No delay in therapy if the mechanism of SVT is not

known.

• Perform CAROTID SINUS MASSAGE,or give 6mg

bolus adenosine.

• In case of severe hemodynamic compromise a

synchronised cardioversion to be given.

Carotid sinus massage

• Check for carotid bruit before massage.

• At the level of cricoid cartilage,at the angle of mandible the carotid sinus is situated.

• Gentle pressure is applied over the carotid sinus for 5 -10 seconds.

• ECG recording to be present.

• In case of no response – try on the other side.

• Simultaneous pressure not to be applied both sides.

• Alternative manuevres are valsalva,gag reflex,ice water pouring over the face.

• If SVT is suspected to be AVnode dependent –

drug of choice is adenosine and CCBs

verapamil and diltiazem.

• But digoxin,BBs,CCBs better control of

ventricular response in atrial tachycardias

• Class I agents to be combined with AV nodal

blocking drugs – to eliminate 1:1 conduction

of atrial to ventricles.

HEMODYNAMIC

STATUS

STABLE BP

>90/60 mmHg

Narrow QRS

and regular

R-R

Vagal maneuveres

IV adenosine

IV verapamil,diltiazem

IV sotalol

Refractory

Wide QRS

complex

Vagal manuevres

IV adenosine

procainamide

Digoxin

Verapamil

Are contraindicated

UNSTABLE

BP< 90/60 mmHg

Direct cardioversion

DRUG DOSE SIDE EFFECTS

AV NODAL BLOCKERS

ADENOSINE 6-12 mg bolus Flushing ,dyspneaChest pain

VERAPAMIL 0.15 mg/kg over 2 min Hypotension bradycardia

DILTIAZEM 0.25-0.35 mg/kg -2 min same

DIGOXIN 0.5-1.0 mg --- 2-10 min Digoxin toxicity

PROPANOLOL 1-3mg over I min Hypotension bradycardia

CLASS I AAD QUINIDINE 6-10MG/KG at 10 mg/min hypotension

PROCAINAMIDE 10-15mg/kg at 50 mg/min hypotension

DISOPYRAMIDE 1-2 mg/kg at 10 mg/min hypotension

PROPAFENONE 1-2mg/min at 10 mg/min Bradycardia,GI disturbance

FLECAINIDE 2 mg/kg at 10 mg/min Bradycardia,dizziness

CLASS III SOTALOL 1-1.5mg/kg at 10 mg/min Hypotension,proarrythmic

AMIODARONE 1.5 mg/kg during 15 min Hypotension,bradycardia

Pill in the pocket approach In whom recurrences are infrequent.

But sustained.well tolerated hemodynamically.

Patients who have had only a single episode of SVT..

100-200mg of flecainide at the onset of SVT is a reasonable approach…until he reaches the hospital.

40-160 mg verapamil –without preexcitation,

Betablockers

Propafenone 150-450 mg.

80% cases interrupted with a combination of CCBand BB in 2 hrs…

Long term control of SVT

• Frequency and severity of episodes.

• LVF

• Cost benefits of radiofrequency ablation over the pharmacotherapy .

• Pharmacotherapy is considered in patients who defer catheter ablation,whom in which ablation failed,or carries a risk of AV block.

• Multifocal atrial tachycardia, Accessory pathway – class Ia,Ic,III

• AV node blocking drugs

• Young patients – Ia drugs

• Class I agents LVD < 35% not used.

Long term treatment

Membrane active AAD

Catheter ablation

Curative surgery

Antitachycardiapacing

Adenosine

not to be used in bronchospastic pulmonary disease.

Adenosine precipitates asthma

Given rapidly in 1-2 sec.

If given by peripheral vein uplift the arm..

Max dose is 30 mg

6- 12-12 mg

Terminates AVNRT .AFL with 2:1 block

Potentiated by dipyradimole,carbamazepine –decrease dose to 3 mg.

Other drugsCalcium channel blockers,beta blockers ,digoxin

are the next drugs to be used if not responded to adenosine

Usually 60 % cases respond to a dose of 6 mg and 95 % cases at 12 mg.

Type 1 a AAD, 1c,iii,AMIODARONE in refractory cases.

Beta blockers not to used IV in heart failure.

Long term treatment in case of recuurentepisodes,hemodynamic instability.

Catheter guided Radiofrequency Ablation

• Several multipolar catheters are introduced

• High right atrium ,bundle of his ,RVapex,Coronary sinus.

• Radiofrequency is delivered at the site of earlier activation

• Success is defined by elimination of the tachycardia or loss of pre excitation.

• 90-98% success in AV node dependent

• 60-80% in case of AV node independent.

• Cryoablation more useful…

Catheter Ablation of Cardiac Arrhythmias.

Some important points

• When the QRS complex is wide and VT is mistaken as

SVT with ABERRANT conduction IV verapamil – not

recommended decreases BP.

• If DC cardioversion to be avoided because of possible

adverse response to digitalis adm …pacing Rt atrium and

ventricle via temp pacing.

• In WPW syndrome avoid VERAPAMIL,LIDOCAINE .

• Avoid digoxin.

• In SANRT –class IA,IC ,BB

• SANRT –digoxin.

Cont…

• Rx of ectopic atrial tachycardia – consider digitalis

toxicity,chronic lung disease,metabolic

abn,electrolyte abnormalities,acute MI ----temporary

pacing

• Removal or reversal of inciting factor

• Surgical excision of focus.

• Rx of MAT –chronic lung disease,metabolic,rare is

digitalis toxicity ---CCBS,BBs ..no role of

cardioversion,devices ,surgery.

In case of WPW syndrome

symptomatic concealed or

manifested ..and evidence of

preexcitation on NSR …send the

patient for catheter ablation…

Special problems

• 1.Coexisting Double Tachycardias• May not be identified during noninvasive testing ..needs EP

study.

• Ex—typical AVNRT and AT.

• Concentric –eccentric –concentric.

• AVNRT –both APC,VPC

• AT only APC

• 2.Pseudo AF- infrequent presentation of PSVT.

• Occurs during onset and termination of tahcycardia.

• Multiple accessory AV pathways.

• In young who have AF without other risk factors.

• 5% of AVNRT.

• Group beating is seen

Thank you