The American Heart Hospital Journal
• the absence of an RS complex in all precordial leads; • an R to S wave interval of more than 100 ms in any of the precordial lead;
• the presence of atrio-ventricular dissociation; and • the presence of morphologic criteria for VT in leads V1–2 and V6.
The presence of any of these criteria supports the diagnosis of VT. Morphologic criteria for right bundle branch block
for lead V1 are: the presence of monophasic R wave, QR or RS morphology; for lead V6: Larger S wave than R wave, or the presence of QS or QR complexes. For left bundle
branch block morphology the criteria include: for V1–2: an R wave of more than 30 ms duration, notching of the
downstroke of the S wave, or duration from the onset of the QRS to the nadir of S wave of more than 70 ms; for lead
V6: the presence of a QR or RS complex. For the final assessment at least one criterion for both V1–2 and V6 have to be present to diagnose VT. Although this is an excellent
protocol, with a sensitivity of 88–92 % and specificity of 44–73 % for VT, it requires remembering multiple morphologic criteria.25,26
The majority of the protocols use
supraventricular tachycardia as a default diagnosis of wide QRS complex tachycardia. Only the presence of specific ECG criteria is used to diagnose the arrhythmia as VT. Unlike previous protocols, VT was used as a default diagnosis by Griffith et al.27
Only the presence of typical
bundle branch criteria assigned the arrhythmia’s origin to be supraventricular. A Bayesian diagnostic algorithm, with assignment of different likehood ratios of different ECG criteria from historically published protocols used by Lau et al., was found to have very good diagnostic accuracy.28 However, this protocol did not incorporate certain important features, such as atrioventricular dissociation, as they could not be ascertained in all cases. Interestingly enough, no statistically significant difference in sensitivity and specificity was found between the Brugada, Griffith and Bayesian algorithm approaches.25
In 2007, Vereckei et al. proposed an algorithm for the differentiation of monomorphic wide QRS complex tachycardias.26
Table 2: Factors Increasing the Likelihood of Ventricular Tachycardia when Reviewing Wide QRS Complex Tachycardias
1. Appropriate ‘substrate’ 2. Atrio-ventricular dissociation, capture and fusion beats 3. QRS axis of -90º to -180º 4. Change in QRS axis by more than 40° 5. Narrowing or QRS complex with tachycardia 6. Positive R wave in lead augmented vector right
Table 1: Summary of the Brugada and Vereckei Protocols Step Brugada et al.24
Vereckei et al. (#1)26
I The absence of The presence of an RS complex atrio-ventricular
in all precordial dissociation leads
II An R to S wave The presence of an The presence of an interval of more initial R wave in initial q or r wave of more than
aVR
100 ms in any precordial lead
III The presence of A QRS morphology The presence of a notch atrio-ventricular that is different from on the descending limb dissociation
bundle branch block of a negative onset and or fascicular block predominantly negative QRS complex
IV The presence of The ratio of the sum of voltage changes of the morphologic initial over the final 40 ms of the QRS complex criteria for VT being less than or equal to one
in leads V1-2 and V6
(as
described earlier in this text)
aVR = augmented vector right; aVR = augmented vector right; VT = ventricular tachycardia.
>40 ms duration
Review
Vereckei et al. (#2, based solely on lead aVR)29 The presence of an initial R wave
This algorithm has a better sensitivity and specificity than the Brugada criteria being 95.7 and 95.7 %, respectively.26 More recently, a new protocol using only lead aVR to differentiate wide QRS complex tachycardias was introduced by Vereckei et al.29
It consists of four steps:
It consisted of four steps. If a patient meets a criteria at any step then the diagnosis of VT is made, otherwise one proceeds to the next step. The four criteria are:
• the presence of atrio-ventricular dissociation; • the presence of an initial R wave in lead aVR; • a QRS morphology that is different from bundle branch block or fascicular block; and
• the algebraic sum of the voltage of the first 40 ms divided by the last 40 ms is less than or equal to one.
Summer 2011
• the presence of an initial R wave; • the presence of an initial q or r wave of > 40 ms duration; • the presence of a notch on the descending limb of a negative onset and predominantly negative QRS complex; and
• the ratio of the sum of voltage changes of the initial over the final 40 ms of the QRS complex being less than or equal to one.
Similar to the previous algorithm, only one of the four criteria needs to be present. The sensitivity and specificity of this protocol are 96.5 and 95.7 %, respectively, which is similar to the previous alghorithm published by this group.29
To reinforce the material we would like to offer Approach to the Differentiation of Wide QRS Complex Tachycardias 35
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