Saturday, July 29, 2023

ECG Blog #388 — Why Does Lead V1 Look Funny?

The ECG in Figure-1 was obtained from an 18-year old woman — who moments before been resuscitated from out-of-hospital cardiac arrest.

In light of the above clinical history ...
  • How would YOU interpret her post-resuscitation ECG?
  • Does this ECG in Figure-1 provide clue(s) to the etiology of this patient's cardiac arrest?

Figure-1: The initial ECG in today's case — obtained following resuscitation from cardiac arrest of an 18-year old woman.
(NOTE: The filter setting used a 150 Hz high-frequency cutoff.)

MY Initial Thoughts on Today's Case:
Today's tracing was sent to me. When I first saw this ECG — I had more questions than answers ...
  • The "good news" — is that we clearly see sinus P waves in ECG #1, that document conversion to sinus rhythm (ie, upright P waves in lead II that precede each QRS complex with a constant and normal PR interval).
  • The challenging part of the 12-lead tracing seen in Figure-1 — is WHY does an 18-year old woman have such a wide and bizarre QRS morphology? I suspected the answer resides in the reason why an 18-year woman might have a cardiac arrest.

Looking Closer at QRS Morphology in ECG #1:
At first glance — I thought we were simply looking at a very wide and bizarre QRS complex, especially in lead V1 (where the QRS looked to measure at least 0.15 second).
  • The all-upright QRS in lead V1 — together with wide terminal S waves in lateral leads I and V6 — is consistent with complete RBBB (Right Bundle Branch Block).
  • The rS configuration with predominant negativity in all 3 inferior leads — is consistent with associated LAHB (Left Anterior HemiBlock) — therefore RBBB/LAHB = Bifascicular Block.
  • In addition — there seemed to be significant fragmentation (excessive notching of the QRS) — which usually is indication of underlying "scar" from infarction, cardiomyopathy, or other form of underlying structural disease.

CASE Follow-Up:
At this point — I learned answers to some of the questions I raise above:
  • The 18-year old woman whose post-resuscitation tracing is shown above in Figure-1 — was found to have ARVC/ARVD (Arrhythmogenic Right Ventricular Cardiomyopathy or Dysplasia).

  • Genetic testing confirmed ARVC (The patient had a homozygous DSG2 gene — associated with both autosomal dominant and autosomal recessive forms of ARVC). 
  • The patient's younger brother was also diagnosed with "a cardiomyopathy".
  • Echo showed a markedly dilated cardiomyopathy (EF ~22% with global hypokinesis, including severely dilated RV with impaired RV function).
  • MRI confirmed ARVC.
  • An ICD (Implantable Cardiac Defibrillator) was inserted — and the patient was discharged from the hospital. This young woman did well for a year — but unfortunately suffered another cardiac arrest, from which she could not be resuscitated.

About ARVC/ARVD ...
ARVD is a genetic disorder of the myocardium. As a result of a familial gene mutation — there is fatty infiltration of the RV free wall (Shah et al — Stat Pearls-NCBI-2022). First described by Guy Fontaine in 1977 — the disorder has a prevalence of ~1/5,000 in the general population.
  • Clinically — the concern is the high risk of developing VT with a LBBB pattern (indicative of the RV origin of VT).
  • Overall, by way of perspective — ARVD is an uncommon disorder. That said — ARVD appears to be an underestimated cause of SCD (Sudden Cardiac Death), especially among younger adults, in whom it accounts for ~20% of SCDs in those under 35 (Mu et al — Medicine 96(47):e8808, 2017)

  • KEY Point: All-too-often the diagnosis of ARVD is only made postmortem. This is particularly unfortunate — because life-prolonging treatment (in the form of ICD implantation) is available.
  • The ECG may provide revealing clues to the diagnosis of ARVD — but as discussed below, there are important caveats to be aware of when interpreting an ECG in which you are considering the possibility of ARVD.
  • Echo may provide helpful clues (ie, by showing a dilated right ventricle, with a very thin RV free wall — and — impaired RV function).
  • Definitive diagnosis may be made by endomyocardial biopsy — or more commonly in recent years, by MRI — in association with genetic testing.
  • Genetic testing of relatives is essential to prevent undetected disease in family members.

Can You Diagnose ARVD from QRS Morphology During the VT?
As suggested above — ARVD is surprisingly common among the potential causes of sudden death in a “previously healthy” younger adult population. Many of these patients have no symptoms prior to their presentation with a 1st (and unfortunately – sometimes also their last) episode of VT. Among those patients who are successfully resuscitated — the question arises as to IF it is possible to diagnose ARVD as the cause from QRS morphology on the ECG obtained during the episode of sustained VT? Insight into this question is provided by 2 Hoffmayer et al manuscripts (JACC 58(8):831-838, 2011 — andFront Physiol 3:23, 2012).
  • VT in patients with ARVD usually arises from the RV. As a result — an “lbbb-like” QRS morphology is typically seen during VT in the chest leads. That said — the frontal plane axis may be variable, depending on where in the RV the greatest pathology is found, and whether RV fatty infiltration is diffuse or more localized.
  • Another cause of variable (sometimes unpredictable) QRS morphology during ARVD-associated VT — is that some patients also have LV involvement, which can be the source of resultant VT (Ghannudi et al — Clin Med Insights Cardiol 8(Suppl 4):27-36, 2014).

  • Clinically — The differential diagnosis for an episode of sustained VT in a previously healthy young adult features some form of idiopathic VT (most commonly RVOT VT = Right Ventricular Outflow Track VT) vs AVRD. Overall, between these 2 principal considerations — RVOT VT is by far, the more common entity. That said, given the more lethal prognosis of ARVD — it is essential not to overlook this diagnosis (especially since ARVD is not as rare as is thought by many).

  • NOTE: The presence of QRS fragmentation and/or recognition of multiple QRS morphologies during repeat episodes of sustained VT are 2 ECG findings that favor AVRD (ie, RVOT VT typically lacks fragmentation [because by definition there is no underlying structural heart disease] — and RVOT tends to only manifest a single QRS morphology [whereas ARVD is more likely to manifest multiple VT morphologies, especially if fatty infiltration involves multiple areas within the RV]).

  • BOTTOM Line: QRS fragmentation and multiple VT morphologies are not reliably seen in all patients with ARVD. As a result — sensitivity and specificity of ECG characteristics during a VT episode are far from perfect for predicting which patients are likely to have ARVD. That said, clinically — this does not matter in an emergency situation because initial management (ie, with drugs or synchronized cardioversion) is essentially the same! And, in 2023 — virtually any young adult with an episode of VT should have follow-up evaluation including cardiac MRI to rule out mimics of severe underlying cardiac pathology, such as ARVD or sarcoidosis with cardiac involvement. Cardiac MRI will then tell you if ARVD is or is not present (Macias et al — JAFIB 7(4):106-111,2015).

When to Suspect ARVD from the 12-Lead ECG:
Awareness of the ECG signs of AVRD may facilitate diagnosis:
  • T wave inversion in right-sided leads V1,V2,V3 is almost always seen — so much so, that the diagnosis of ARVD becomes unlikely if right-sided T wave inversion is missing.
  • There may be localized QRS widening (to ≥110 msec.) in these right-sided leads.
  • The most specific diagnostic ECG sign of ARVD is the Epsilon wave (Pérez-Riera et alInd Pacing Electrophys J 19:63-67, 2019). These elusive ECG deflections are thought to represent delayed potentials from slow intraventricular conduction (due to fatty infiltration, mixed with fibrous tissue within remnants of normal myocardium)
  • That said — Epsilon waves are often of limited diagnostic value, because: i) Technical oversights reduce detection, even in patients with these deflections; and, ii) Epsilon waves are generally a manifestation of more advanced disease.

Why is it hard to pick up Epsilon Waves on ECG?
  • There are several reasons ...  

Reason #1: The Wrong Filter Setting is Used ...
All too often — filter settings are ignored. Different settings are typically used for monitoring when emphasis is placed on rhythm determination vs diagnostic mode, for which the focus is on interpreting 12-lead waveforms. Greater filtering is generally used in monitor mode, with a common setting between 0.5 Hz and 40 Hz. Doing so has the advantage of minimizing artifact and baseline wander that may affect rhythm interpretation. In contrast — a broader passband (typically from 0.05 Hz to 150 Hz) — is recommended for diagnostic mode, where more accurate ST segment analysis is essential.
  • I've taken Figure-2 from the illustration by García-Niebla et al (Rev Esp Cardiol 69(4):438, 2016) — to show how selection of a 40 Hz cutoff frequency (that is commonly chosen in clinical practice in an attempt to "improve" tracing appearance) may result in reduction (if not disappearance) of fine ECG features such as the Epsilon wave, that is only optimally seen in Figure-2 at a cutoff high-pass filter setting of 150 Hz (BLUE arrows). 
Figure 2: Illustration of the effect of filter settings on the likelihood of seeing epsilon waves on a standard 12-lead ECG.

Reason #2: The Wrong Lead System is Used ...
I strongly recommend the section by Drs. Buttner and Cadogan in Life-In-The-Fast-Lane on the Fontaine Lead — — as this concise review outlines what to know for optimizing your chance of identifying an Epsilon wave on ECG. I highlight below a few KEY points from this LITFL Review:
  • Identification of an Epsilon wave is the most specific ECG sign of ARVD. These small deflections may be seen as a "blip" or "wiggle", most often occurring either at the end, or just after the QRS complex — but definitely before the T wave. Epsilon waves are best seen in leads V1,V2 — and a bit less well seen in V3,V4. On occasion — they may also be seen in other leads.
  • LITFL cites a figure of 23% for the frequency of visualizing epsilon waves on a standard ECG in patients with ARVD. The filter settings used in association with citation of this figure are not mentioned — so given the tendency of all-too-often selecting a 40 Hz high-pass setting (instead of the optimal 150 Hz setting) — an even lower likelihood of finding epsilon waves might be expected on the ECGs sent our way in search of detecting Epsilon waves.
  • In contrast — use of special placement of standard ECG machine electrodes called Fontaine Lead Placement — allows detection of Epsilon waves in up to 75% of patients! Rather than reproducing the user-friendly instructions on the LITFL site — I'll refer interested readers directly to their site — —

  • Finally — Be aware of the variety of potential Epsilon wave shapes! These include: i) "Wiggle" waves; ii) Small upward spikes; iii) Small downward spikes; and/or, iv) Smooth amplitude deflections at the end of the QRS (which may result in prolongation of the QRS in right-sided leads by up to 25 msec.).


Take Another LOOK at Today's Tracing:
"Armed" with the above insight regarding ECG detection of Epsilon waves — Let's take another LOOK at today's initial ECG (Figure-3).

  • How would you now interpret the initial ECG in today's case?
  • Do you see Epsilon waves in Figure-3? If so — in which lead(s)?

Figure-3: The initial ECG in today's case — that I've reproduced from Figure-1. This ECG was obtained following resuscitation from cardiac arrest of an 18-year old woman. (NOTE: The filter setting used a 150 Hz high-frequency cutoff.)


ANSWER: Interpretation of Figure-3 . . .
I fully acknowledge that prior to 2010, when I started my ECG Blog and began my heavy involvement in ECG internet consultation — I had no direct experience with Epsilon waves. While I still find exposure to this intriguing ECG phenomenon uncommon — I've become much more comfortable with its detection.
  • The ECG in today's case provides the BEST illustration of Epsilon waves that I too-date have seen.

Figure-4: I've labeled the ECG in Figure-3 — to highlight how to identify the numerous Epsilon waves present in today's tracing.

My Observations regarding Figure-4:
The rhythm in Figure-4 is sinus — as evidenced by regular upright in lead II P waves, with a constant and normal PR interval.
  • As we noted in the beginning of today's post — the QRS complex is wide, with QRS morphology consistent with RBBB/LAHB.
  • Note that there is T wave inversion in the anterior leads, as would be expected with ARVD (albeit the presence of RBBB itself could account for some of this anterior T wave inversion).

  • KEY Point: The reason for the bizarre shape of the QRS complex in lead V1 — is that the QRS in this lead is being prolonged by a huge Epsilon wave (dark BLUE arrow).

  • To assist in looking for Epsilon waves in other leads — I dropped a vertical dark BLUE time-line through the peak of the huge Epsilon wave in lead V1 — extending downward through the long lead II rhythm strip at the bottom of the tracing. Doing so defines the point in the 2 simultaneously-recorded long lead rhythm strips that marks the occurrence of the Epsilon wave.
  • Using this reference point we defined for the Epsilon wave in the long lead II and lead V1 rhythm strips — I then extended upward a vertical light BLUE time-line to highlight the expected location of any Epsilon waves that might be seen in simultaneously-recorded leads I,II,III — aVR,aVL,aVF — and V4,V5,V6.
  • The light BLUE arrow in lead II highlights a surprisingly large negative Epsilon wave that is present in this lead.
  • Following these upward extended light BLUE time-lines — we can see that smaller, but definitely-present negative Epsilon waves are also seen in leads I, aVL, aVF, and V3-thru-V6.
  • Another positive Epsilon wave is seen in lead aVR.


Acknowledgment: My appreciation to Mubarak Al-Hatemi (from Qatar) for the case and this tracing. 



ADDENDUM (7/29/2023):

I summarize KEY features regarding Idiopathic VT in Figure-4.

Figure-4: Review of KEY features regarding Idiopathic VT (See text).

ECG Media PEARL #14 (8 minutes Audio) — What is Idiopathic VT? — WHY do we care? Special attention to the 2 most common forms = RVOT (Right Ventricular Outflow Track) VT and Fascicular VT.



Related ECG Blog Posts to Today’s Case:

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.
  • ECG Blog #185 — Reviews the Ps, Qs, 3R Approach to Rhythm Interpretation.

  • Please see My Comment at the bottom of the page in the June 3, 2023 post in Dr. Smith's ECG Blog — in which a case of ARVC is reviewed.

  • ECG Blog #220 — Review of the approach to the Regular WCT (Wide-Complex Tachycardia).
  • ECG Blog #196 — Reviews another Case with a Regular WCT Rhythm

  • 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 Pearl in this blog post.
  • ECG Blog #211 — WHY does Aberrant Conduction occur?

  • ECG Blog #197 — Review of Fascicular VT.
  • ECG Blog #301 — Reviews a WCT that is SupraVentricular! (with LOTS on Aberrant Conduction).

  • ECG Blog #38 and Blog #85 and Blog #323 — Review of Fascicular VT.
  • ECG Blog #278 — Another case of a regular WCT rhythm in a younger adult.
  • ECG Blog #35 — Review of RVOT VT.
  • ECG Blog #42 — Criteria for distinguishing VT vs Aberration.

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