A 70 something male presented in severe respiratory distress.
The patient had altered mental status and so he was prepared for intubation. Before intubation, he became hypotensive.
On the monitor patient had wide-complex tachycardia.
The following 12-lead was obtained:
Differential is ventricular tachycardia versus supraventricular tachycardia with aberrancy versus sinus tachycardia with a aberrancy.
There are possible P waves in lead II. But these could be an extension of the QRS, so sinus tach is not certain. Certainty could come with the use of Lewis leads. Much easier is to see if the rate varies from moment to moment, especially if it decreases with supportive care.
This QRS is not typical of any kind of bundle branch block, which makes aberrancy much less likely. Given that this QRS looks nothing like any normal kind of a aberrancy, it is reasonable to use electrical cardioversion.
Here is a normal LBBB:
Given patient's acute drop in his blood pressure, the patient was cardioverted with synchronized cardioversion at 200 J with no change in his rhythm.
But why does this EKG look nothing like left bundle branch block?
After the patient was stabilized with supportive care, the heart rate gradually slowed, confirming sinus tachycardia.
A thoracotomy scar was found on his right chest.
A Chest X-ray was obtained:
The providers were able to find some previous history: On chart review patient has a history of left bundle branch block and so this is likely sinus tachycardia in the setting of a left bundle branch block. He also had a history of lung cancer with pneumonectomy and COPD. His presentation was consistent with a severe COPD exacerbation.
Here is a subsequent CT slice of heart in chest
This explains the very abnormal wide complex QRS. It is a left bundle branch block that is distorted due to the grossly abnormal location of the heart.
The heart rate gradually slowed with supportive care.
Here is a subsequent rhythm strip:
- From a purely ECG interpretation standpoint — How would you interpret today's rhythm?
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| Figure-1: The initial ECG in today's case. Is this sinus tachycardia or VT? |
- Looking at the ECG in Figure-1 — I was uncertain if we were seeing atrial activity. On the one hand — the pointed, upright deflection seen at the end of each T wave in lead II could be a sinus P wave — in which case, the rhythm would be sinus tachycardia at ~130/minute (within the RED circle in lead II of Figure-2, shown below).
- On the other hand — we lack clear demarcation between this upright, pointed deflection and the T wave in front of it — raising the question as to whether this deflection is really a P wave? – OR, terminal positivity from the T wave? — OR, a combination of a P wave with some terminal positivity from the preceding T wave? And, if this pointed deflection was the end of the T wave (and not a P wave) — then today's initial rhythm could be VT!
- Editorial NOTE: In my experience — there is almost always a readily identifiable negative deflection that appears before the QRS complex in lead V1 when the rhythm is sinus tachycardia with LBBB. I do not see this in today's initial tracing — which simply means that I did not know for certain if the rhythm was an SVT (ie, sinus tachycardia or a reentry SVT) — or — whether the rhythm might be VT.
- KEY Point: Distinction between sinus tachycardia with LBBB vs VT is crucial — since synchronized cardioversion would be indicated for VT in this patient with marginal respiratory and hemodynamic status — but contraindicated if the rhythm is sinus tachycardia. This is not an easy clinical distinction to make in today’s case.
- QRS Morphology during the WCT: As a single tracing standing alone in the absence of additional information — QRS morphology is not consistent with LBBB conduction (either from preexisting LBBB or from rate-related LBBB aberrant conduction). While true that the all upright QRS complexes in lateral leads are as expected for LBBB conduction (BLUE arrows in Figure-2) — I have never seen LBBB conduction that produces all positive QRS complexes beginning as early as in lead V2, and continuing through to lead V6 (RED arrows in leads V2,V3,V4 of Figure-2). Instead — one rarely sees an initial R wave as tall as 6 mm in lead V1 when there is LBBB conduction (as per the GREEN arrow we see in Figure-2) — and predominant negativity of the QRS complex should be present and persist with LBBB conduction at least until lead V3 — and more often through lead V4 or V5.
- Finding a prior tracing on today’s patient in sinus rhythm with QRS widening — could be enlightening IF QRS morphology during sinus rhythm was identical to that shown in Figure-2 (in which case — the baseline tracing might reveal that the patient had been in an unusual form of IVCD all along).
- KEY Point: Everything changes as soon as you see this patient’s chest X-Ray (Insert at the bottom of Figure-2). This patient in severe respiratory distress clearly shows sufficient abnormalities on chest X-Ray that could plausibly account for the highly unusual QRS morphology in Figure-2 (whereas in a patient without such extensive pulmonary disease — such QRS morphology would simply not be consistent with LBBB conduction).
- ECG assessment of regular WCT rhythms without clear delineation of sinus P waves is an imperfect science. Statistically, in unselected cases — about 80% of such rhythms will turn out to be VT. This figure increases to ~90% even before you look at the ECG, if the regular WCT rhythm in question is from an adult of “a certain age” and the patient has a history of underlying heart disease.
- Additional criteria can help to refine this 90% estimate. This includes assessment of the frontal plane Axis during the WCT (ie, VT becomes much more likely if the QRS during WCT is all negative either in lead I or in lead aVF).
- Assessment of some simple features regarding QRS morphology during the WCT may prove especially helpful. For example — VT becomes much more likely if QRS morphology during WCT is not consistent with some known form of conduction defect (See My Comment in the May 5, 2020 post in Dr. Smith's ECG Blog for more on "My Take" re criteria for distinguishing between SVT vs VT).
- Finding a prior tracing on the patient when in sinus rhythm with QRS widening may support the presence of a preexisting unusual morphology of conduction defect, thereby confirming an SVT rhythm.
- And when sinus tachycardia is suspected (albeit with an unusual QRS morphology) — a number of simple measures can provide the answer! Record frequent hard copy of serial tracings! The KEY characteristic of sinus tachycardia — is that the rate of sinus tach should change with time, depending on whether the patient’s clinical condition is getting better or worse. For example, in today’s case — slight clinical improvement resulted in modest slowing of the heart rate — which turned out to be enough to now see enough clear delineation between P wave and T wave to prove that the rhythm was truly sinus tach all along, but with a very unusual QRS morphology.
- Final Consideration: When confronted with an unexpectedly unusual form of QRS morphology — Go to the bedside and LOOK at the patient! Think "out of the box" about other potential reasons that might explain such an unexpected morphology (ie, pulse-tap artifact; unusual body habitus, chest bandages or chest tubes — or, as in today's case — severe pulmonary pathology that may alter the ECG recording).
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| Figure-2: I’ve labeled today’s initial tracing and have added this patient’s chest X-ray. |
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