vt in structurally normal heart

VENTRICULAR TACHYCARDIAIN

STRUCTURALLY NORMAL HEART

Dr. Pruthvi PuwarDNB Cardiology

Vijaya Hospital Chennai

WIDE COMPLEX TACHYCARDIA Definition Importance of History Clinical examination ECG features

DEFINITION

Wide QRS complex tachycardia is a rhythm with a rate of more than 100 b/m and QRS duration of more than 120 ms

VT (80%)

SVT (20%)

VT- Non-sustained VT: three or more ventricular beats with a

maximal duration of 30 seconds. Sustained VT: a VT of more than 30 seconds duration (or less if

treated by electrocardioversion within 30 seconds). Monomorphic VT: all ventricular beats have the same

configuration. Polymorphic VT: the ventricular beats have a changing

configuration. The RR interval is 180-600 ms Biphasic VT: a ventricular tachycardia with a QRS complex

that alternates from beat to beat. 

SVT- a tachycardia dependent on participation of structure at or above bundle of His LBBB morphology- QRS > 12 msec. with prominent negative

deflection in V1

RBBB morphology- QRS > 12 msec. with prominent positive deflection in V1.

POINTS IN HISTORY DIAGNOSIS

H/O MI VT

H/O CHF VT

H/O ANGINA VT

Recurrent episodes SVT

Duration of illness >3 years SVT

Minimally symptomatic events including palpitations and light headedness without syncope

SVT

Each has a PPV of 95%

PHYSICAL EXAMINATION Signs of AV dissociation favours VT - varying intensity of S1 - variation of systolic BP - hypotension

Termination of WCT with maneuvers ~ carotid,vasalva,adenosine favours SVT

BRUGADA CRITERIA

OTHER ECG FINDINGS FAVOUR VT

North - west QRS axis deviation i.e superior and rightward minus 90 degree to 180 degree

Negative or positive concordance of QRS complex in all precordial leads

AV dissociaton : Fusion beats, capture beats In LBBB, QRS duration >160 ms In RBBB,QRS duration > 140 ms Previous ECG show MI

RABBIT EAR IN RBBB PATTERN

POSITIVE CONCORDANCE

FUSION & CAPTURE BEATS

ECG strip shows series of ectopic beats (a run of Vtach; the ectopic rhythm) followed by capture beats (normal configuration; the sinus rhythm) and then a gradual merging of the capture beats into the ectopic beats. 

New aVR algorithm

Vereckei et al;Heart Rhythm 2008 483 WCT (351 VT, 112 SVT, 20 preexcited tachycardia)

analysed Greater sensitivity for VT diagnosis than Brugada

algorithm(96.5% vs 89.2%, P .001) Greater specificity for diagnosing SVT compared with

Brugada criteria

András Vereckei, MD et al Heart Rhythm, Vol 5, No 1, January 2008

AVR ALGORITHM

If the distance traveled on the Y axis in the initial 40ms of the QRS complex is smaller than that traveled in the terminal 40ms of the QRS complex, a VT is much more likely

ULTRASIMPLE BRUGADA CRITERION: RW TO PEAK TIME (RWPT)

In 2010 Joseph Brugada et al. published a new criterion to differentiate VT from SVT in wide complex tachycardias: the R wave peak time in Lead II [4].

They suggest measuring the duration of onset of the QRS to the first change in polarity (either nadir Q or peak R) in lead II. If the RWPT is ≥ 50ms the likelihood of a VT very high (positive likelihood ratio 34.8).

VT IN STRUCTURALLY NORMAL HEART: Idiopathic Ventricular tachycardia 10% patients with VT Structural heart disease can be ruled out if -

ECG, ECHO and CAG are normal However , MRI can detect RVOT origin VT despite

all modalities being normal

SPECT – single photon emission CT

IDIOPATHIC VT Subclassified based on several criterias:

mechanism, location, response to therapy

OUTFLOW TRACT TACHYCARDIAS IDIOPATHIC LEFT VTs (ILVT) AUTOMATIC VTs

RVOT VT (80-90% of VT) ILVT (idiopathic LV outflow tract) IPVT (idiopathic propranolol sensitive VT) CPVT (catecholaminergic polymorphic VT) Brugada Syndrome Long QT syndrome

VT IN STRUCTURALLY NORMAL HEART:

Inherited Ion-channelopathies

Taken from Supplement of JAPI , 2007

OUTFLOW TRACT TACHYCARDIA Account for most cases (80-90%) Outflow tract encompases RV region between

pulm & tricuspid valves; AND basal left ventricle (including LVOT, aortic cusps)

Most commonly presenting as VPCs, Monomorphic nonsustained VT

Sustained VT less common Ppt: Exercise, emotional stress, exercise testing,

menstrual cycles in female

DAD mediated triggered activity

Typically mediated by intracellular calcium overload through increased intracellular cAMP

This explains Sensitivity to beta-blockers, CCBs

MECHANISM

Lerman et al, Circulation 1995, 92

RVOT VT: RV monomorphic extrasystoles are considered

benign This may progress to ARVD or RVOT VT, with MRI

evidence of functional/anatomical abnormality ECG: LBB morphology, inferior Axis, QRS

transition in V3/V4 Common in females of 30-50 yr age Palpitation, presyncope, syncope (less common) Exercise or emotional stress Sudden death is rare

Two phenotypic forms: Non-sustained repetitive monomorphic VT Paroxysmal exercise induced sustained VT

Classification based on site of origin: Originating from pulmonary artery RV-end outflow tract

RVOT VT:

LBBB and inferior axis Right sided origin- LBBB pattern with transition from a small r-wave to a large R-wave at V3 to V4

RVOT VT

RVOT region can be divided into nine regions

Anterior sites demonstrate Q wave (Q or qR) in lead I and QS in lead aVL

Posterior sites demonstrate R wave in lead I and early precordial transition (R> S in V3)

Between anterior and posterior locations typically demonstrate a multiphasic QRS morphology in lead I

JADONATH AND COLLEAGUES

Differentiation of septal from free wall RVOT VT RVOT VTs originating from septum - taller,narrower monophasic R waves in inferior leads Free wall RVOT VT- typically broader QRS (>140ms) and R wave notching in inferior leads Later transition in precordial leads (>V4)

DIXIT AND COLLEAGUES

Atriofascicular fibers (Mahaim fibers)AVRT using Rt-sided accessory pathwayVT after repair of TOFARVD

DIFFERENTIAL DIAGNOSIS OF RVOT VT

ECG during VT shows S wave in lead I R-wave transition in lead V1or V2(Earlier precordial transition zone) More rightward axes Taller R waves in inferior leads

LVOT VT – - CLINICALLY SAME LIKE RVOT VT- MECHANISM ALSO SAME

S wave in LI and R-wave transition in V1 suggest LVOT VT. R:S amplitude ratio of 30% and R:QRS duration ratio of 50% Presence of an S wave in leads V5 and V6 suggests an

infravalvular origin of the tachycardia.

May originate from supravalvular or infravalvular endocardial region of coronary cusp of aortic valve Distinction is important –RF ablation

LVOT VT

RVOT VT Vs aortic cusp VT

R wave duration and R/S wave amplitude ratio in leads V1 and V2 were greater in tachycardias originating from cusp compared with RVOT

Precordial lead transition earlier in cusp VT occurring before lead V3

Absence of an S wave in V5 or V6 -specificity of 88% for cusp VT compared with RVOT VT

OUYANG AND COLLEAGUES

TREATMENT

• Usually benign course

• Good prognosis

1. May respond acutely to carotid sinus massage, Valsalva maneuvers or intravenous adenosine or verapamil

2. Long-term oral therapy with either BB or CCB 3. Non-responders (33%)- class I or III

antiarrhythmic agents

RFA

1. When medical therapy is ineffective or not tolerated

2. High success rate (>80%) 3. Ablation of epicardial or aortic sinuses sites is

highly effective 4. Technically challenging and carries higher risks

-proximity to coronary arteries5. Recurrence 10%

15 to 40 years

More in men (60%)

Most occur at rest

Usually paroxysmal

Incessant forms leading to TCM are described

IDIOPATHIC LEFT VT

Re-entrant mechanism

Lower turnaround point is toward the apex

Retrograde limb is formed by Purkinje network

ELECTROPHYSIOLOGIC MECHANISM

Baseline 12-lead ECG is normal in most patientsExit near the area of the left posterior fascicle RBBB + left superior frontal plane axis Relatively narrow QRS duration (<140 msec) RS interval <80 msec Exit near the area of the left anterior fascicle RBBB+ right frontal plane axis

Long-term prognosis is very goodPatients who have incessant tachycardia may develop a tachycardia related cardiomyopathy Intravenous verapamil is effective in acutely terminating VTMild to moderate symptoms oral –verapamilBB and class I and III antiarrhythmic agents useful in some Medical therapy is often ineffective in patients who have severe symptoms

RFAAssociated with significant symptoms or who are intolerant or resistant to medical therapy Post ablation: 10% chances of recurrence (either ILVT or RVOT-VT) of different morphology

Requires re-ablation

AUTOMATIC VENTRICULAR TACHYCARDIAIPVT: PROPRANOLOL SENSITIVE A form of IVLT <50 yr, often ppt by exercise Can arise from anywhere within heart Unresponsive to Verapamil Beta blockers very effective in terminating

VT Chances of SCD ICD recommended in survivors

AHA/ESC GUIDELINES RECOMMENDATIONS FOR TREATMENT: Class IC: catheter ablation useful in drug

refractory and symptomatic pts or in pts who are intolerant to longterm drug therapy

Class IIa: 1. EP study reasonable for diagnosis in suspected outflow

tract VT (LOA: B)2. BB/CCB can be useful for symptomatic VT arising from

RVOT (LOA: C)3. ICD – can be effective therapy for sustained VT who are

receiving chronic drug therapy & who have reasonable expected survival for more than 1yr (LOA:C)

LIFE-THREATENING(TYPICALLY POLYMORPHIC VT)

• Rare • Generally occurs with genetic ion channel disorders • Unlike monomorphic VT, associated with SCD • Abnormalities exist at molecular level

Genetic syndromes

1. Long QT

2. Brugada Syndrome

3. CPVT

LIFE-THREATENING(TYPICALLY POLYMORPHIC VT)

LONG QT SYNDROME

Corrected QT interval 440 ms in men and 460 ms in women with or without morphological abnormalities of the T waves Decrease in outward potassium currents or increase in inward sodium currents Prolongs repolarization phase of cardiac action potentialResult in prolongation of QT interval Predisposition to torsade de pointes VT

Seven types, based on different genes involved LQT1, LQT2, and LQT3 account for 90%LQT1 and LQT2 -mutations of KCNQ1 and KCNH2 genes that encode subunits of IKs and Ikr potassium channels, respectively LQT3 -mutations of SCN5A gene that encode subunits of INa sodium channels Approximately 25% not have identifiable gene mutations

• Mean age of symptom onset is 12 years• Present with syncope, seizures, or cardiac arrest. • Clinical presentation and ECG repolarization (ST-T) patterns

have been correlated to genotype

LQT1 -often have broad-based T waves and frequently experience events during physical activity (especially swimming).

LQT2- T-wave is often notched in multiple leads.

Triggers for LQT2 include startling auditory stimuli (e.g., from an alarm clock) and emotional upset.

LQT3- often demonstrate long ST segments

Most LQT3 events occur at rest or sleep.

MANAGEMENT

1. Avoid trigger events and medications prolong QT interval

2. Risk stratification schemes based on degree of QT prolongation, genotype, and sex

3. Corrected QT interval exceeding 500 ms poses a high risk for cardiac events

4. Patients who have LQT2 and LQT3 may be at higher risk for SCD compared with patients who have LQT1

TREATMENT

1. BB are indicated for all patients with syncope and for asymptomatic patients with significant QT prolongation (IB)

2. Role of BB in asymptomatic patients with normal or mildly prolonged QT intervals remains uncertain.

3. BB are highly effective in LQT1, but less effective in other LQTS

4. Role of BBs in LQT3 is not established.

5. Because LQT3 is a minority of all LQTS,symptomatic patients who have not undergone genotyping should receive BBs

• ICD are indicated for secondary prevention of cardiac arrest and for patients with recurrent syncope despite BB therapy

• Less defined therapies

• Gene-specific therapy with mexiletine , flecainide , or ranolazine for some LQT3 patients

• PPI for bradycardia

• Surgical left cardiac sympathetic denervation for recurrent arrhythmias resistant to BB therapy (class IIb, LOA-B)

• Catheter ablation of triggering PVCs-abolish recurrent VT/VF

BRUGADA SYNDROME

• Characterized by coving ST-segment elevation in V1 to V3

• 2 mm in 2 of these 3 leads are diagnostic

• Complete or incomplete RBBB pattern

• Pattern can be spontaneously present or provoked by sodium-channel– blocking agents such as ajmaline,flecainide, or procainamide

• Typical ECG pattern can be transient and may only be detected during long-term ECG monitoring.

CLINICAL PRESENTATION

• Syncope or cardiac arrest

• Predominantly in men in third and fourth decade

• Also been linked to SCD in young men in Southeast Asia and has several local names,including Lai Tai (“died during sleep”) in Thailand

• Prone to atrial fibrillation and sinus node dysfunction

TREATMENT• No well-validated preventive medical therapy

• Patients who don’t have cardiac arrest risk stratified on the basis of spontaneous ECG pattern and syncope

• Lowdose quinidine may be used to treat frequent VAs in patients who already have an ICD (Class IC)

• Quinidine and isoproterenol may be useful in patients having VT storms

• Catheter ablation of triggering PVCs and ablation of RV outflow epicardial musculature successful in abolishing recurrent VT/VF in a small number of patients

ROLE OF ICD

• ICD are effective in preventing SCD and are indicated for cardiac arrest survivors (Class IC)

• Major management dilemma arises in decision to place prophylactically an ICD based on patient’s perceived risk of SCD

1. Patients with spontaneous ECG pattern and syncope are at high risk and ICD insertion is generally recommended for primary prophylaxis

2. Asymptomatic patients with spontaneous ECG pattern are at intermediate risk, and their best therapeutic options may need to be individualized (class IIC)

3. Asymptomatic patients without spontaneous ECG pattern are at low risk and may be followed up clinically

4. Family history of SCD and specific genotypes do not predict events

Disorder of myocardial calcium homeostasis

Clinically manifested as exertional syncope and SCD due to exercise induced VT

Often polymorphic or bidirectional

CATECHOLAMINERGIC PMVT.

• Autosomal dominant form involves mutation of cardiac ryanodine receptor (RyR2 gene) in approximately 50% of patients

• Autosomal recessive form, accounting for only 3% to 5% of genotyped cases-mutations of calsequestrin 2 gene (CASQ2)

• RyR2 and CASQ2 mutations cause intracellular calcium overload and DAD -basis of arrhythmogenesis

• Resting ECG is unremarkable

• Typical VT patterns are reproducible with exercise or catecholamine infusion

• VAs typically appear during sinus tachycardia rates of 120 beats/min to 130 beats/min, with progressive frequency of PVCs followed by bursts of bidirectional VT

• Mean age for presentation with syncope is 7.8 - 4 years

• Electrophysiology study is not helpful in risk stratification

• Mainstay of medical management is BB therapy

• 46% may have recurrent events while receiving therapy

• CCB may have limited effectiveness as adjunctive therapy

• Flecainide blocks RyR2 receptor and shows promise as a medical therapy

• ICD insertion is appropriate for patients who had cardiac arrest and with life-threatening VA despite maximal medical therapy

• Recurrent ICD shocks may occur and an initial shock with its accompanying pain and anxiety may trigger further VAs

• Surgical left cardiac sympathetic denervation -resistant cases

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