V tach is identified by: wide QRS complexes (>.12 seconds), rate faster than 100 bpm. In MONOMORPHIC V tach, all QRS complexes look alike. There are other mechanisms of wide-complex tachycardia, but they can be difficult to differentiate from a single rhythm strip. All WCT should be treated as V tach until proven otherwise.
This ECG is from a man who was experiencing palpitations and light-headedness with near-syncope. On first look, you will see a wide-complex tachycardia (WTC) with a rate around 240 per minute. It is difficult to assess for the presence of P waves because of the rate and the baseline artifact.
This wide-complex tachycardia is ventricular tachycardia. Along with the wide QRS and the fast rate, features which favor a diagnosis of VT over BBB include: backwards (extreme right) QRS axis, negative QRS in V6, and an apparently monophasic QRS in V1, as opposed to the rSR' pattern of right bundle branch block.
Remember, ALL wide-QRS t
This ECG was donated to the ECG Guru by Brent Dubois, and was originally published on the FaceBook page, Paramedic Tips & Tricks. We published it to this site three years ago, but believe it should be shown again, as it is somewhat rare to catch a good-quality 12-Lead ECG of an implanted cardioverter-defibrillator pacemaer using overdrive pacing to terminate a ventricular tachycardia. Most of our examples have been rhythm strips.
INTERPRETATION: Ventricular tachycardia (rate about 163/min) presumably originating from the left ventricle (LV).
Overwhelming evidence that this is ventricular tachycardia are as follows:
1.) The ventricular tachycardia is apparently dissociated from a sinus tachycardia at a somewhat slower rate of about 123/min (best seen in leads V1 and aVL; vertical arrows). While not nearly as clinically significant as those types of double tachycardia caused by digitalis intoxication, this example might technically qualify as a form of “double tachycardia” since both the upper and lower chambers of the heart are exceeding a rate of 100/min.
2.) The duration of the QRS interval is so-called “wide-wide” (i.e., > 0.14s) at about 0.19s to 0.20s.
3.) The predominantly negative rS complex in Lead I and wholly negative QS complex in aVF indicate an axis of roughly about -120 and would place it in the right upper quadrant (i.e., “No-Man’s-Land” or “N-M-L”). This is suggestive of an apical origin of the tachycardia.
4.) Brugada criterion # 1: There are no RS complexes in any of the V leads (here they’re either qR or QS complexes.) Brugada pointed out that if none of the V leads contained a diphasic RS complex, then there was no need for any further analysis, the tachycardia was unequivocally ventricular in origin. 2
5.) The presence of a monophasic QS complex in V6 is more diagnostic of ventricular tachycardia than just a rS complex; especially if associated with a QRS complex in V1 that is predominantly positive. By Dr. Marriott’s estimation, this combination only occurs in about 20% of all left ventricular tachycardias (LVT).
6.) Cogent evidence arguing against this being the result of conduction over an accessory pathway are threefold:
a. The wholly negative QS complexes from V4-6 are also suggestive of an apical origin of the tachycardia. Since all accessory pathways enter the ventricles at their base, accessory pathway conduction is effectively excluded; and . . . 1
b. . . . a qR complex in any of the five leads, V2-6 (here in V2-3) also excludes preexcited (W-P-W) tachycardia; and . . . 1
c. . . . the presence of more QRS complexes than P-waves (because in any form of preexcited tachycardia, the atria are involved in every beat). 1
7.) The QRS complex in V1 is not a monophasic R-wave. Rather it is a diphasic qR complex with very subtle notching / slurring on the downstroke (oblique arrow) of the R-wave (i.e., so-called taller left “rabbit-ear” equivalent.)
8.) The q-waves in V1-3 are superficially mimicking the negative component (i.e., nadir) of an atrial flutter wave but right-sided chest leads do not usually show the typical “saw-tooth” pattern so often seen in inferior leads II, III, and aVF. Atrial flutter waves in V1 usually take on the appearance of little positive “P-like” waves. What looks like a retrograde atrial impulse immediately following a QRS complex in V4 is actually part of the QRS complex itself.
References / Sources.
1.) Marriott, HJL. Emergency Electrocardiography. Naples, Fl.: Trinity Press, 1997, p. 60 - 71.
2.) Nelson's EKG Site: http://nelsonsekgsite.com/
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