APPROACH TO WIDE QRS COMPLEX TACHYCARDIA

KUSH KUMAR BHAGATDM CARDIO

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%)

WHY IS IT IMPORTANT TO DIAGNOSE….?

Right diagnosis is important in management

Incorrect decision or indecision can worsen the status

APPROACH TO THE EVALUATION OF WIDE COMPLEX TACHYCARDIAS

History Physical Examination The Electrocardiogram Algorithms Electrophysiologic Testing

UTILITY OF HISTORY IN MAKING A DIAGNOSIS

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%

SVT VS VTPHYSICAL EXAMINATION

Physical findings that indicate presence of AV dissociation (cannon A waves, variable-intensity S1,variation in BP) if present are useful

Termination of WCT in response to maneuvers like Valsalva, carotid sinus pressure, or adenosine is strongly in-favor of SVT but there are well-documented cases of VT responsive to these

ELECTROCARDIOGRAPHIC FEATURES Several features of the ECG in WCT have proven

diagnostic utility; the more important among these include the following

1. QRS Duration - a wider QRS duration favors VT. In RBBB-like WCT, a QRS duration more than 140

milliseconds suggests VT, whereas in LBBB-like WCT, a QRS duration more than 160 milliseconds suggests VT.

Rarely, VT can have a relatively narrow QRS duration (less than 120 to 140 milliseconds) can be observed in fascicular (verapamil-sensitive) VT.

2. QRS Axis-. A significant axis shift (more than 40 degrees) between

the baseline NSR and WCT is suggestive of VT.

A right superior (northwest) is rare in SVT and strongly suggests VT.

In a patient with an RBBB-like WCT, a QRS axis to the left of −30 degrees suggests VT.

in a patient with an LBBB-like WCT, a QRS axis to the right of +90 degrees suggests VT.

RBBB with a normal axis is uncommon in VT (less than 3%) and is suggestive of SVT

LBBB morphology with RAD

o 3. Precordial QRS Concordance- Concordance is present when the QRS complexes in the six precordial leads (V1 through V6) are either all positive in polarity (tall R waves) or all negative in polarity (deep QS complexes).

o Because concordant patterns are present in <20% of all VTs, this criterion has low sensitivity.

o In some cases of LBBB aberration, R waves may not be seen until V7 or later, leaving a concordant negative pattern. 

o A more recent analysis found that a negative concordant pattern had virtually no capacity to distinguish SVT-A from VT, but a positive concordant pattern remained a strong differentiator.

Miller JM, Das MK, Yadav AV, et al.: Value of the 12-lead ECG in wide QRS tachycardia. Cardiol Clin. 24:439-451 2006 16939835

Concordant pattern.

The left panel shows a VT arising in the apical area of the left ventricle resulting in negative concordancy of all precordial leads.

In the right panel ventricular activation starts in the left posterior area, resulting in positive concordancy of all precordial leads.

4. Atrioventricular Dissociation:

When the P waves can be clearly seen and the atrial rate is unrelated to and slower than the ventricular rate, AV dissociation consistent with VT is present

AV dissociation is the hallmark of VT (specificity is 100%; sensitivity is 20% - 50%).

Fusion Beats- Ventricular fusion occurs when a ventricular ectopic beat and a supraventricular beat (conducted via the AVN and HPS) simultaneously activate the ventricular myocardium.

The resulting QRS complex has a morphology intermediate between the appearance of a sinus QRS complex and that of a purely ventricular complex.

Dressler Beats or a capture beat- is a normal QRS complex identical to the sinus QRS complex, occurring during the VT indicates that the normal conduction system has momentarily captured control of ventricular activation from the VT focus.

Fusion beat and capture beat

Ventriculoatrial conduction with blockApproximately 30% of VTs have 1 : 1 retrograde ventriculoatrial (VA) conduction 15% to 20% have second-degree (2 : 1 or Wenckebach) VA block.

5. QRS Morphology- As a rule, if the WCT is caused by SVT with aberration, then the QRS complex during the WCT must be compatible with some form of BBB that could result in that QRS configuration.

• If there is no combination of bundle branch or fascicular blocks that could result in such a QRS configuration, then the diagnosis by default is VT.

• WCTs can be classified as having an RBBB-like pattern or an LBBB-like pattern.

• In the patient with a WCT and positive QRS polarity in lead V1 (RBBB pattern), a monophasic R, biphasic qR complex, or broad R (more than 40 milliseconds) in lead V1 favors VT

• A double-peaked R wave in lead V1 favors VT if the left peak is taller than the right peak (the rabbit ear sign)

• An rS complex in lead V6 is a strong predictor of VT (likelihood ratio more than 50 : 1)

In RBBB pattern first “rabbit ear” is taller in VT while second “rabbit ear” is taller in SVT.In LBBB pattern the time from R-wave start to S-wave nadir is short in SVT and long in VT.

• In the patient with a WCT and a negative QRS polarity in lead V1 (LBBB pattern), a broad initial R wave of 40 milliseconds or more in lead V1 or V2 favors VT,

• Notching in the downstroke of the S wave, or an RS interval (from the onset of the QRS complex to the nadir of the S wave) of more than 70 milliseconds in lead V1 or V2 favors VT.

• Any Q wave in V6 favours VT

FINDINGS IN LEAD V1 AND V2 DURING LBBB SHAPED TACHYCARDIA POINTING TO A VENTRICULAR ORIGIN

the presence of any of these three criteria in lead V1 (broad R wave, slurred or notched downstroke of the S wave, and delayed nadir of S wave) is a strong predictor of VT (likelihood ratio, more than 50 : 1).

WELLEN’S CRITERIA ( VT FAVOURED IN THE PRESENCE OF )

AV DISSOCIATION LEFT AXIS DEVIATION CAPTURE OR FUSION BEATS QRS ≥ 140 msec PRECORDIAL QRS CONCORDANCE RSR’ IN V1, MONO OR BIPHASIC QRS IN

V1,OR MONOPHASIC QS IN V6

Wellens HJJ, Bar FWHM, Lie KI. The value of theelectrocardiogram in the differential diagnosis of a tachycardia

with a widened QRS complex. Am J Med 1978;64:27-33[Medline].

WELLEN’S CRITERIA

KINDWALL’S CRITERIA FOR VT IN LBBB

R wave in V1 or V2 >30 ms. Any Q wave in V6. Onset of QRS to nadir of S wave in V1 or

V2 > 60 ms. Notching on the downstroke of the S wave

in V1 or V2.

Kindwall KE, Brown J, Josephson ME: Electrocardiographiccriteria for ventricular tachycardia in wide

complex left bundle branch block morphology tachycardia.Am J Cardiol 61:1279, 1988.

BRUGADA CRITERIA

SENSITIVITY 89.2%SPECIFICITY 73.2%NEGATIVE PREDICTIVE VALUE 67.2%POSITIVE PREDICTIVE VALUE 91.2%

Step 1

ECG THAT DEMONSTRATES POSITIVE CONCORDANCE, STEP ONE OF BRUGADA CRITERIA NOTE THE ABSENCE OF AN RS COMPLEX

Step 2

Step 3

STEP 4: LBBB - TYPE WIDE QRS COMPLEX

SVT VT

small R wave notching of S waveR wave >40ms

fast downslopeof S wave

no Q wave

Q wave

> 70ms

V1

V6

STEP 4: RBBB - TYPE WIDE QRS COMPLEX

SVT VT

V1

V6

or

or

R/S > 1 R/S ratio < 1 QS complex

rSR’ configuration monophasic R wave qR (or Rs) complex

GRIFFITH ALGORITHM VT UNLESS OTHERWISE PROVED!

Lancet 1994 Feb. 12,343(8894)386-388

SENSITIVITY FOR VT 90%SPECIFICITY 67-85%

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

Vereckei proposed two algorithms incorporating lead aVR.Reasons for using aVR:

During SVT w/ BBB, the initial rapid septal activation and the later main ventricular activation wavefront move away from lead aVR, creating a negative QRS complex in lead aVR

Initial dominant R wave in aVR is incompatible w/ SVT, its presence suggest VT, typically originating from the inferior or apical region

The first had four steps (a positive result at any step makes a VT diagnosis, with the remaining ECGs categorized as SVT-A)

VERECKEI ALGORITHM

Vereckei A et al. Eur Heart J 2007

NEGATIVE PREDICTIVE VALUE 83.8%POSITIVE PREDICTIVE VALUE 92.4%

VENTRICULAR ACTIVATION VELOCITY RATIO VI/VT

Vi – initial ventricular activation velocity

Vt – terminal ventricular activation velocity

Measured by the excursion (in mV) during the initial (Vi) and terminal (Vt) 40 msec of the QRS complex

Vi/Vt <= 1,supports VT

Principle: Rapidity of initial septal activation with SVT as compared to VT

SVT with aberrancy-initial activation is rapid VT-initial ventricular activation slow due to muscle

to muscle spread of activation

This algorithm performed well in initial testing but is somewhat cumbersome, and it is difficult to remember how to make the measurements.

The second proposed algorithm involves only aVR and thus is generally simpler.

It also consists of four steps: 

AVR ALGORITHM

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

SENSITIVITY 96.5%SPECIFICITY 75%NEGATIVE PREDICTIVE VALUE 86.6%POSITIVE PREDICTIVE VALUE 92.7%

CAVEATS OF VI/VT CRITERIA

A scar situated at a late activated ventricular site can result in a decreased Vt in the presence of VT, leading to the misdiagnosis of SVT

In fascicular VT, the Vi is not slower than the Vt

MODIFIED BRUGADA/PAVA CRITERIA

Pava et al proposed another simple, one-step criterion: the interval from QRS onset to peak amplitude (positive or negative) in lead 2.

Using a cutoff of 50 ms, almost all WCTs with a shorter time to peak amplitude in lead 2 were SVT, whereas almost all WCTs with intervals ≥50 ms were VT.

The proposed rationale to analyze lead II is that it is a lead that is easy to obtain and is commonly represented as a rhythm strip on ECG or ECG monitors.

SENSITIVITY 93.2%SPECIFICITY 99.3%POSITIVE PREDICTIVE VALUE 98.2%NEGATIVE PREDICTIVE VALUE 93.3 %

J Brugada/Pava et al Heart Rhythm 2010;7:922–926

CAVEATS OF PAVA CRITERIA

Inability to accurately define the initiation and peak of QRS complexes

Fascicular VT and Bundle branch re-entry VT may have a shorter RWPT due to their origin within or in close proximity to the His-Purkinje network.

Although this criterion appears to have many desirable features—simplicity, ease of application, accuracy—its performance in the hands of other investigators has been less impressive (sensitivity 0.60, specificity 0.83).

BRUGADA/STUERER ALGORITHM FOR VT V/S PRE EXCITED SVT

the predominant polarity of the QRS complex in leads V4 through V6 is defined as positive or negative

a qR complex in one or more of precordial leads V2 through V6

1:1 AV relationship

Positive

Absent

VT Sp 100%, Sn 64%

VT Sp 100%,Sn 75%

V>A Waves VT Sp100%,Sn 75%

SVT

Negative

Present

Absent

Present/Absent with A >V waves

Sn75%/25% are still VT

Gunter Steurer ,Pedro Brugada et al Clin. Cardiol. 17, 306-308 (1994)

SPECIFICITY 100%

SENSITIVITY 75%

ACC/AHA ALGORITHM

Blomström-Lundqvist and Scheinman et al. Circulation 108:1871,2003,

IRREGULAR WCT

AF + BBBConsistent QRS morphologyRate limited by AV node (usually <

200bpm)

Atrial flutter with variable block + BBBFlutter waves present, some not conductedConsistent QRS morphologyConsistent R-R interval in groups

AF + WPWQRS morphology variationRates can approach 300bpm

MAT + BBB Irregular P waves of different morphologyConsistent QRS morphology Inconsistent R-R interval

Polymorphic VTQRS morphology variation (more chaotic

than WPW)Rates consistently rapid (often > 300bpm)Unstable

ELECTROPHYSIOLOGICAL TESTING His Bundle–Ventricular Interval- When

the His bundle–ventricular (HV) interval is positive (i.e., the His potential precedes the QRS onset), an HV interval during the WCT shorter than that during NSR (HVWCT less than HVNSR) indicates VT or preexcited SVT

an HVWCT equal to or longer than HVNSR indicates SVT with aberrancy.

When the HV interval is negative (i.e., the His potential follows the QRS onset), SVT with aberrancy are excluded.

SUMMARY

Arriving at the correct diagnosis of tachycardia has obvious clinical importance, in that current therapies can cure many disorders thereby preventing further episodes.

In cases of WCT, many algorithms have been proposed to differentiate between the two major causes: VT and SVT-A. Although each algorithm is introduced with great promise, each has its limitations.

The ideal algorithm would be one that is (1) easy to remember, (2) universally applicable to all WCTs, (3) easy to apply with unequivocal results, and (4) 100% sensitive and specific for VT (or SVT).

Until such a tool is developed, it is safest to treat the patient with WCT that cannot be readily classified for whatever reason as though the rhythm is VT, until proven otherwise.

TAKE HOME MESSAGE

VT>>SVT

When in doubt treat as VT

Do not hesitate to shock if hemodynamic instability is present

Brugada`s is not the only criteria, it`s time to move on!!

Never make the mistake of rejecting VT because the broad QRS tachycardia is haemodynamically well tolerated.

THANK YOU