Pragmatic Approach How to Diagnose Ventricular Tachycardia in Cardiac Telemetry
v062221
By: @ecgrhythms
What is a wide complex tachycardia?
A wide complex tachycardia (WCT) is defined as a cardiac rhythm with a rate of > 100 bpm and QRS width/duration ≥120 ms or 0.12 sec. Other acronym used is WQRST.
WCT are described as right bundle branch block (RBBB) - like configuration or left bundle branch block (LBBB)-like configuration.
A RBBB is recognized by a QRS duration ≥ 120 ms with a predominantly positive portion in V1 (Figure 1A). LBBB has QRS duration of ≥120 ms with a predominantly negative terminal portion in V1 (Figure 1B).
Figure 1 – A. RBBB
configuration in V1. B. LBBB configuration in V1.
What
are the probabilities of a Wide Complex Tachycardia (WCT)?
A WCT can be any of the following:
- Ventricular Tachycardia (VT) ~ 80%
- Supraventricular tachycardia (SVT):
- with aberrancy in the His-Purkinje system
- with anterograde accessory pathway conduction
- with bizarre baseline QRS
- in presence of drug effect or electrolyte imbalance
- Ventricular pacing
- Electrocardiogram artifact
A Short Review of Aberrancy
Technicians often used other terms instead of aberrancy like bundle-switch, intermittent bundle, conduction change and intermittent ventricular conduction delay. However, the appropriate term should be aberrancy or aberrant intraventricular conduction.
Figure 2 - Cardiac
Conduction System
The purpose of arriving at the correct diagnosis is to avoid harm to the patient. If SVT is treated as VT and given amiodarone or electrical cardioversion (which may not be harmful) it is not the optimal therapy. If it was atrial flutter, cardioversion will entail a risk of stroke. If VT is treated as SVT (using diltiazem/verapamil), hemodynamic deterioration may occur. If SVT are managed as VT, they might be placed on long-term amiodarone which carries a number of long-term problems or an implantable defibrillator with repeated generator change. However, hunting the diagnosis is second only to stability of the patient. If the patient is unstable then immediate cardioversion and then once stable the various morphological characteristics and algorithms are used.
Figure
3 – Typical Central Telemetry Set-up
What
are the ECG Criteria or Algorithms for the Diagnosis of VT?
The following are the criteria and algorithms
to differentiate VT from SVT with aberrancy:
·
Sandler
and Marriot Criteria (1965)
·
Wellens
Criteria of RBBB (1978)
·
Kindwall
criteria of LBBB (1988)
·
Brugada
algorithm (1991)
·
Griffith
algorithm (1994)
·
Bayesian
analysis (2000)
·
Vereckie
algorithm I (2007)
·
Vereckie
algorithm II (2008)
·
Pava
Criteria of lead II (2010)
·
VT score
(2014)
·
Limb
Lead Algorithm (2019)
What
are ECG Criteria/Features that are practical or useful in cardiac
telemetry?
The
following are useful to diagnose VT:
·
The
Initiation "Logic" ("K. Wang Logic")
·
R wave Peak Time in Lead
II (Pava Criteria)
·
aVR
algorithm (Vereckie algorithm)
The Initiation (“K. Wang Logic”)
According to Dr. K Wang (and as mentioned in Chou's Electrocardiography in Clinical Practice), it is easy to identify VT and SVT with aberrancy if the initial or baseline is sinus rhythm. There are 3 things to remember.
1.
When the run of WCT is preceded by a premature P wave (often the P wave
has a different morphology), then it is SVT with
aberrant conduction.
The ECG case above (Figure 4) is from a 75 yr old patient with pontine
infarct with several episodes of wide and narrow complex tachycardia. After 3
narrow QRS complexes, a PAC can be seen right after R3 (orange
arrow) conducted with a long PRI. The WCT (~150 bpm) then starts. The
initiation by a PAC is typical of AV nodal reentry tachycardia which is one of
the SVT's. (Please refer to separate discussion on SVT's).
2. If the WCT is preceded by a regularly (not prematurely) occurring sinus P wave (the PR interval is shorter than that of normally conducted sinus beats), it is ventricular tachycardia. (Figure 5)
Figure 5 – A WCT preceded by a regular sinus P wave with short PRI
3. If the WCT is not preceded by a P wave, it is ventricular tachycardia. (Figure 6)
Figure 6 – A WCT not preceded by a P wave
Figure7 - An Flow Diagram on Initiation Logic
Figure
7 shows the diagram to simplify the 3 events.
During VT, there is independent beating of the atria and ventricles (AV Dissociation). In patients with underlying sinus rhythm, the atria are depolarized by an impulse coming from the sinoatrial (SA) node while the ventricles are controlled by an ectopic ventricular beat (Figure 8) . The atrial rate is slower compared to the ventricular rate. AV dissociation is difficult to spot but not impossible. AV dissociation is easier to see in slower VT but difficult to appreciate during fast rates. Multiple simultaneous leads are needed to compare distortions and determine if those distortions are indeed P waves.
Look for AV dissociation in the case below. Map the P waves and the QRS.
Figure 8 – WCT case
for AV dissociation
Distinct P waves are marked in red arrows and not so obvious P waves are marked with blue arrows (Figure 9). To check if those are indeed real P waves, you can do simultaneous lead comparison. Take for example the identified P wave before R5. The P wave is upright in II and aVF and inverted in aVR. Other P waves in this case are hidden from view or are buried in the QRS. From 2 sequential P waves, we can then use a caliper to march the P waves.
Figure 9 – P waves
marked with arrows
The P to P interval is 18 small boxes (cycle
length 720 ms) or an atrial rate of about 83 bpm. The R to R interval is 14 small boxes (cycle
length 540 ms) or a ventricular are of about 107 bpm. At that rate difference,
we can see dissociation. Another way of visual recognition is using a ladder
diagram (Figure 10). However, this might be time consuming in the acute
setting. For educational purposes the ladder diagram is presented below. The
diagram will show independent beating of the atria and ventricles or AV
dissociation.
Figure
10 – Ladder diagram showing AV dissociation
The ventricles may be also be depolarized both by the ectopic ventricular impulse and a supraventricular impulse resulting in a QRS complex that is intermediate in morphology between the sinus beat and the ectopic ventricular beat. This complex is a fusion beat.
The previous ECG case featuring AV dissociation will be used. In the strip below (Figure 11), the morphology of R4, R10 and R16 is different compared to the rest of the R waves. The duration of these 3 R waves is about 0.12 seconds (vs. 0.16 sec).
Figure 11 – Fusion
beats highlighted with arrows
The reason for the difference in QRS morphology is because R4, R10 and R16 are fusion beats. This is best illustrated in the ladder diagram (Figure 12).
Figure 12– Ladder
diagram showing fusion beats
Below (Figure 13) is another example of a fusion beat (red arrows) which supports that the WCT is VT and not SVT with aberrancy. The first 4 complexes are sinus beats. After the 5th complex is the full duration of the WCT. If you only use leads II and V1, it will be difficult for you to appreciate the difference in the shape of complex #5 which is a fusion beat. However, if you use full disclosure to see all limb leads, you will appreciate that complex #5 is different in shape from the first 4 complexes and the WCT.
Figure 13 – Fusion
beat highlighted by arrows
During slower VT, occasional supraventricular impulse may be transmitted through the AV node and depolarize the ventricles resulting in a normal looking QRS (capture beat) in the middle of wide QRS beats.
The interval of a capture beat is shorter than during the tachycardia or its rate is faster compared to the WCT.
The complexes below (red box) are captured beat (Figure 14). It has the same morphology or shape with that of a sinus beat (latter part of the strip). The presence of the capture beats means that the WCT is VT.
Figure
14 – Capture beats highlighted in red box
VT
is the likely diagnosis if the RWPT in lead II is ≥ 50 ms.
The sensitivity, specificity and positive
predictive value of RWPT in lead II are 93.2%, 99.3% and 98.2%, respectively.
The other name of RWPT in lead II is the Pava
Criteria based on the first author of the paper.
Figure
15 - How to measure the RWPT
Figure 16 are examples of different QRS
morphologies in lead II with RWPT ≥
50 ms .
Figure 16 - Representative samples of
different RWPT ≥ 50 ms (Figures
from Jastrzebski M, et al. 2016. The
ventricular tachycardia score: a novel approach to electrocardiographic diagnosis
of ventricular tachycardia. Europace 18, 578–584)
The typical secondary lead in cardiac telemetry is lead V. It is usually placed in the V1 position. Some of the telemetry systems have 6 wires. The 4 wires are for the limbs and the other 2 wires are chest leads. These 2 wires can be positioned in the V1 and V6 position.
The following morphology in V1 and V6 supports VT:
• RBBB-VT or Wellen's RBBB-VT criteria (Figure 17)
v V1 - Monophasic R, QR, or RsR’ (rabbit ear with right greater than left)
v V6 – R/S ratio < 1, QR or QS, monophasic R
• LBBB-VT or Kindwall LBBB-VT Criteria (Figure 18)
v V1- Initial r > 30 ms, nadir of S > 60 ms, notched downstroke
v V6 – any q, QS or QR
Figure
17 – V1 and V6 morphology criteria for VT (top) and SVT with RBBB morphology
(bottom)
(From Garner J and Miller J. 2013. Wide
Complex Tachycardia – Ventricular Tachycardia or Not Ventricular Tachycardia, That
Remains the Question. Arrhythmia &
Electrophysiology Review 2013;2(1):23–29)
Figure
18 – V1 and V6 morphology for VT (top) and SVT with LBBB morphology (bottom)
(From
Garner J and Miller J. 2013. Wide Complex Tachycardia – Ventricular Tachycardia
or Not Ventricular Tachycardia, That Remains the Question. Arrhythmia & Electrophysiology Review 2013;2(1):23–29)
In VT diagnosis, morphologic stepwise approach was developed. The most popular algorithm developed was the Brugada algorithm. However, the Brugada algorithm cannot be used in cardiac telemetry because it needs a 12L ECG. The new aVR algorithm (Vereckie II) is useful in cardiac telemetry because it only utilizes lead aVR.
The new Vereckie algorithm is shown below (Figure 19 and 20). The algorithm in a stepwise fashion looks at aVR for (1) an initial R wave, (2) initial r or q wave > 40 ms, (3) a notch in the descending limb of a predominantly negative QRS and (4) vi/vt ≤ 1. Vi stands for voltage change in the initial or first 40 ms and vt stands for voltage change in the terminal or last 40 ms. If any of the features mentioned is present then the WCT is VT.
Figure 19 – The New
Vereckie Algorithm
Figure 20 –
Morphologic features supporting VT in the New Vereckie Algorithm (From Garner J
and Miller J. 2013. Wide Complex Tachycardia – Ventricular Tachycardia or Not
Ventricular Tachycardia, That Remains the Question. Arrhythmia & Electrophysiology Review 2013;2(1):23–29)
The limb lead algorithm is another stepwise approach utilizing the limb leads (I, II, III, aVR, aVL and aVF).
In a stepwise fashion is looks at (1) the aVR if monophasic, (2) predominantly negative QRS in I, II and III and (3) the opposing QRS complexes in the limb leads (Figure 21).
Opposing QRS complexes in the limb leads is described as:
· monophasic QRS complexes (QS/R) in all 3 inferior leads sharing the same polarity (all positive or all negative, but including a notched R or QS complex),
· monophasic QRS complexes (R/QS) in 2 or 3 of the remaining limb leads, with a polarity opposite to that of the inferior leads.
If any of the features mentioned is present then the WCT is VT.
Figure 21 - Limb Lead
Algorithm
Figure 22 - The Limb Lead Algorithm
Conclusion
The
diagnosis of VT has undergone evolution. There is still “no one criterion to end all criteria”. If uncertain about the diagnosis
of a WCT, it is wise to treat it
as VT. You will be correct 80% of the time. However, all pragmatic/practical
criteria and algorithms must be used to differentiate VT from SVT with
aberrancy:
·
R wave Peak Time in Lead II (Pava Criteria)
·
aVR algorithm (Vereckie algorithm)
References:
· Blomström-Lundqvist
C, Scheinman M, Aliot E, et al. 2003. ACC/AHA/ESC guidelines for the management
of patients with supraventricular arrhythmias∗—executive summary: a report of the American college of
cardiology/American heart association task force on practice guidelines and the
European society of cardiology committee for practice guidelines (writing
committee to develop guidelines for the management of patients with
supraventricular arrhythmias) Developed in Collaboration with NASPE-Heart
Rhythm Society. J Am Coll Cardiol.
;42(8):1493-1531.
· Bonnow et al. 2014. Braunwald's Heart
Disease: A Textbook of Cardiovascular Medicine. 10th Edition. PA.Saunders
·
Brugada P
et al. 1991. A New Approach to the Differential Diagnosis of a Regular
Tachycardia With a Wide QRS Complex Circulation 83:1649-1659
(http://circ.ahajournals.org/content/83/5/1649)
·
Chen
et al.2019. Simple electrocardiographic criteria for the rapid identification
of wide QRS complex tachycardia: The new limb lead algorithm. Heart Rhythm17:3
431-438
·
Das and
Zipes. 2012. Electrocardiography of arrhythmias: a comprehensive review.
Elsevier PA
·
Fisch C
and Knoebel S. 1992 .Vagaries of Aberrancy. Br Heart J 67:16-24
·
Fisch C and Knoebel SB. 2000.
Electrocardiography of Clinical Arrhythmia. New York. Futura Publishing Co.
·
Fisch C.
1983. Aberration: seventy five years after Sir Thomas Lewis. Br Heart J; 50:
297 -302
·
Fisch C.,
Zipes DP and McHenry PL. 1973. Rate Dependent Aberrancy. Circ 48:714-724
·
Garner J
and Miller J. 2013. Wide Complex Tachycardia – Ventricular Tachycardia or Not
Ventricular Tachycardia,That Remains the Question. Arrhythmia & Electrophysiology Review 2013;2(1):23–29
· Goldberger
A. 2013. Goldberger’s Clinical Electrocardiography : A Simplified Approach 8Ed.
Ph Elsevier
· Issa Z,
Miller J and Zipes D. 2012. Clinical Arrhythmology and Electrophysiology: A
Comprehensive Review - A Companion to Braunwald’s Heart Disease 2nd Ed. PA
Saunders
· Jastrebski
et al. 2016. The ventricular tachycardia score: a novelapproach to
electrocardiographic diagnosis of ventricular tachycardia. Europace
18, 578–584
· Kindwall
at al. 1988. Electrographic Criteria for Ventricular Tachycardia in Wide
Complex Left Bundle Branch Block Morphology. AJC 61: 1279-1283
· Miller et
al. 2006. The Value of 12-Lead ECG in Wide QRS Tachycardia Cardiology Clinics
24:439-451
· Pava et
al. 2010. R-wave peak time at DII: A
new criterion for differentiating between wide complex QRS tachycardias. Heart Rhythm ;7:922–926
· Surawicz B
and Knilans TK. 2008. Chou’s Electrocardiography in Clinical Practice. 6th
ed. PA. Saunders-Elseiver
·
Vereckie A
et al. 2008.New algorithm using only
lead aVR for differential diagnosis of wide QRS complex tachycardia. Heart
Rhythm ;5:89 –98 (http://lab230.com/files/Miller_Criteria_for_wide_complex_tachycardias-_EHJ.pdf)
·
Wang K.
2013. Atlas of Electrocardiography. India. JP Brothers Medical Publishers
· Wellens et
al. The Value of Electrocardiogram in the Differential Diagnosis of Tachycardia
with Widened QRS Complex. 1978. AJM 64: 27-33