Thursday, April 29, 2021

ECG Blog #219 (ECG MP-36) — Is this an Irregular VT?

The 12-lead ECG shown in Figure-1 was obtained from an 87-year-old man who presented to the ED (Emergency Department). Unfortunately — no other information is available on this patient.

  • How would you interpret this tracing?
  • How certain are YOU of your diagnosis?


Figure-1: 12-lead ECG obtained from an 87-year-old man (See text).





NOTE #1: Some readers may prefer at this point to listen to the 7:45 minute ECG Audio PEARL before reading My Thoughts regarding the ECG in Figure-1. Feel free at any time to review to My Thoughts on this tracing (that appear below ECG MP-36).


Today’s ECG Media PEARL #36 (7:45 minutes Audio) — Reviews distinction between Ventricular Tachycardia vs AFib when the Wide Tachycardia is Not Regular.



MY Approach to this Tracing:

As always — I favor use of a Systematic Approach for assessment of every 12-lead ECG I encounter (This Systematic Approach reviewed in ECG Blog 205). The first part of this 12-lead Systematic Approach entails assessment of the Rhythm.

  • Unfortunately — there is no long lead rhythm strip associated with the 12-lead ECG shown in Figure-1. That said — there are more than enough beats on this 12-lead tracing to adequately assess the cardiac rhythm. I favor the Ps, Qs & 3R Approach (Reviewed in ECG Blog 185).
  • P waves are absent.
  • The QRS is wide.
  • Regularity: Although parts of this rhythm look regular — when measured, the R-R interval is constantly changing. The rhythm is irregularly irregular.
  • Rate: The rate is rapid. It looks like the average R-R interval is about 2 large boxes — which corresponds to a rate of ~150/minute (A total of 26 beats are seen on this tracing — which is 10 seconds long — which means the actual rate = 26 X 6 = 156/minute).
  • Related: Since P waves are absent — there is no "relation" between P waves and the QRS.
  • Therefore — The rhythm is AFib with a rapid ventricular response.


PEARLS/Comments regarding this Tracing:

  • Although at times — VT (Ventricular Tachycardia) may manifest an element of irregularity, it should not be as irregularly irregular as the rhythm in Figure-1. This is AFib.
  • Coarse undulations in the baseline (best seen in lead II) represent "fib waves". 
  • Further support that the rhythm in Figure-1 is supraventricular is forthcoming from QRS morphology, which is consistent with RBBB (Right Bundle Branch Block). As reviewed in ECG Blog #204 — ECG diagnosis of the bundle branch blocks is made from assessment of QRS morphology in the KEY leads ( = leads I, V1 and V6) — which show RBBB-equivalent pattern in lead V1 (predominantly upright qR complex in V1 and, wide terminal S waves in leads I and V6.
  • NOTE: Finding a prior ECG on this patient could be very helpful — especially IF you see identical QRS morphology on a prior tracing during sinus rhythm (which would establish beyond doubt that the etiology is supraventricular — and that the rhythm is rapid AFib).
  • QRS morphology in Figure-1 is consistent with a Bifascicular Block = RBBB/LPHB (Reviewed in the video ECG Media Pearl #21which is found in ECG Blog #203). In association with RBBB — a deep and very steep (straight) S wave downslope in lead I suggests LPHB (Left Posterior HemiBlock). LPHB is not common. When seen — it is almost always associated with RBBB, and usually implies significant underlying heart disease.
  • QRS morphology in lead V1 lacks the characteristic triphasic (rsR') appearance of RBBB. The finding of an initial Q wave in lead V1 (which is clearly seen in 6 of the 7 QRS complexes in this lead) — suggests there has been prior septal infarction
  • Although difficult to tell because of baseline undulations — there appears to be a Q wave in lead III — and possibly in lead aVF (at least in some of the complexes in this lead). This is of uncertain clinical significance.
  • There is no sign of chamber enlargement (although assessment of LVH and RVH is always challenging when there is BBB).
  • There are nonspecific ST-T wave changes — but these do not appear to be acute.



NOTE: The reason I departed from  the sequential systematic approach outlined in ECG Blog #205 — is that the QRS complex is wide!

  • The 1st things to do on recognizing QRS widening are: i) Ensure that the patient is hemodynamically stable; andii) Make sure that the rhythm is not VT. As noted above — the absence of P waves and complete irregularity of the rhythm told us this is AFib.
  • Once established that the rhythm is supraventricular — the next step is to determine the type of conduction defect. The reason this should be done before assessing axis, chamber enlargement and QRST changes — is that criteria for these parameters will be different when there is bundle branch block.


In Summary: The ECG in Figure-1 shows AFib with a rapid ventricular response. There is bifascicular block (RBBB/LPHB) — with a Q wave in lead V1 that suggests prior septal infarction. Nonspecific ST-T wave changes are present — but these do not appear to be acute.

  • Finding a prior ECG on this patient would be helpful in determining which (if any) of the above changes might be new.
  • Clinical correlation is needed to determine optimal managment. Unfortunately — no additional clinical information was available on this patient.



Related ECG Blog Posts to Today’s Case: 

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation (outlined in Figures-2 and -3, and the subject of Audio Pearl MP-23 in Blog #205). 
  • ECG Blog #185 — Reviews my System for Rhythm Interpretation, using the Ps, Qs & 3R Approach
  • ECG Blog #204 — Reviews the ECG diagnosis of the Bundle Branch Blocks (RBBB/LBBB/IVCD). 
  • ECG Blog #203 — Reviews ECG diagnosis of Axis and the Hemiblocks. For review of QRS morphology with the Bifascicular Blocks (RBBB/LAHB; RBBB/LPHB) — See the video ECG Media Pearl #21 in this blog post. 
  • ECG Blog #211 — WHY does Aberrant Conduction occur?



  1. AF, S1Q3T3, right axis, RBBB(RVH). What about PE?

    1. A LOT would depend on the History, that unfortunately we do not know … As to an S1Q3T3 pattern — keep in mind that by definition, a RBBB will give you the “S1” — and it also often manifests a “T3” — as lead III is a right-sided lead, so you’ll often see similar findings as you in right-sided lead V1. The patient is elderly (87yo) — and QRST morphology just has a chronic “look” with lots of fragmentation of the QRS complex in many leads, and non-acute ST-T wave changes (ie, the T wave inversion we see in leads V1,V2 and minimally in V3 — but not beyond — is perfectly consistent with the RBBB and the fast rate — and not suggestive of RV “strain”). And the rapid AFib is not an unexpected finding in an 87yo woman.

      Again — we are not privilege to the history. IF the history was new-onset dyspnea — and the AFib and RBBB were new (especially IF there was more ST-T changes suggestive of RV “strain”) — then acute PE would rise to near the top of my list! THANKS for your comment!

  2. We often say that a qR morphology in v1 = atypical RBBB together with findings in lead I and avL. WHen will we then decide that the q wave in v1 represents infarction, and not just an expected finding in atypical RBBB?

  3. Thanks for your comment. It is difficult to answer without having a specific ECG to refer to ... But there are 2 different concepts here. IF the rhythm is supraventricular (ie, not VT) — and there is a wide QRS with predominant positivity in lead V1 and there are wide terminal S waves in lateral leads — then you have defined RBBB conduction. Whether or not a qR or QR pattern in lead V1 in addition represents a septal infarction (or pulmonary hypertension) would then depend on a series of factors, including history — and the rest of the ECG. Even then — we often cannot be certain — so I'll sometimes simply note the presence of a Q in V1 with RBBB and mention that this could reflect prior septal infarction — with need for clinical correlation. I hope this helps to answer your question — :)