Saturday, April 14, 2018

Besides the Nonspecific T-wave Inversion in aVL, What Else is Abnormal on this ECG?

This case was sent by Laszlo Farkas, a paramedic from Hungary.  He discussed it with Janos Borbas MD and Robert Sepp MD from University of Szeged 2nd Department of Internal Medicine and Cardiology Clinic. 

The case inspired me to resurrect a case that I published 10 years ago with the same ECG finding (2nd case below).

What is the finding?

What does it signify?


An elderly male presented with chest pain.  Here is the first ED ECG:
Hint: the finding is NOT the T-wave inversion in aVL

This ECG that I published 10 years ago in Critical Decisions in Emergency and Acute Care Electrocardiography has the same finding:
What is the finding?

The finding is an inverted U-wave, as demonstrated with arrows here:
Inverted U-waves in a patient with chest pain are reported to be highly specific, but insensitive, for ischemia/infarction.

Here is the ECG from Laszlo's case again:
See the inverted U-waves in V3, V4, V5

In Laszlo's case, he recognized it and recorded another ECG 35 minutes later:
Now the U-waves are not the issue.
There is obvious STEMI.

This is after reperfusion and stenting of an occluded LAD:
Terminal T-wave inversion, consistent with reperfusion.

And then 13 minutes later:
Resolution of much of the ST Elevation (but not all).
Now U-waves are upright in V2-V550-70% reduction in STE is good evidence of tissue reperfusion
(there can be reperfusion of the artery without reperfusion of the myocardium, called "No Reflow", and the ECG is the best predictor of reflow, correlating closely with angiographic "myocardial perfusion grade," or "blush")

Here is case 2:

This shows the initial ECG shown again, the comparison ECG from previous, and the reperfusion ECG after stenting of LAD that had severe subtotal thrombotic occlusion with TIMI-2 flow:

This 89 year old had an episode of unresponsiveness. 

Previous ECG:

First ECG with arrows (again)
Slight STD in inferior and lateral leads, some STE in aVL, and profound negative U-waves in V3-V5. 

After Reperfusion of LAD:
Reperfusion T-waves (Wellens' waves)

Short Summary of the U-wave

[Adapted from one of my chapters (in the ACS section, which I edited) in Critical Decisions in Emergency and Acute Care Electrocardiography.  There are some contributions by Farkas Laszlo.]

Note: The research on this topic is not of the most robust quality as the finding is unusual, it is not a common finding, and there is not a lot of angiographic ECG research on this.

A U-wave is a low amplitude, usually positive monophasic deflection after the T-wave, usually with the same vector as the T-wave.  It is co-incident with Phase 4 of the action potential.  The exact etiology of the U wave remains unclear.  Hypotheses include repolorization of the Purkinje fibers and Mechanical Rebound of the myocardium at the end of systole.  It is normally less than 2 mm in height AND less than 25% of the T-wave in height. U wave duration is about 170+-30 ms.  It is usually positive in II, isoelectric in aVL and aVR and may be, less commonly, inverted in III and aVF.  It should be upright in precordial leads.  When inverted in the precordial leads, it implies structural or ischemic heart disease.  It is normally less than 2 mm in height AND less than 25% of the T-wave in height.

What are the implications of negative U-waves?

A negative U-wave, other than in lead aVR, III, or aVF, implies ischemic heart disease. It has been described during variant (vasospastic) angina attacks and during stress testing, under which circumstances it has shown high specificity (though low sensitivity) for the presence of a significant LAD stenosis.  It may also be seen with uncontrolled hypertension, under which circumstances the U wave is usually negative-positive (biphasic), whereas in acute ischemia it is more likely to be positive-negative.  In a patient with acute chest pain, a negative U-wave in the precordial leads represents a significant LAD lesion until proven otherwise.  Interestingly, patients with an anterior wall MI and negative U-waves in the precordial leads have been reported to have smaller infarcts, less STE, better collateral circulation, and a larger amount of stunned but viable myocardium, but the numbers are small.  Similarly, a prominent negative U-wave in all inferior leads in the presence of chest pain may be due to inferior ischemia. This negative U-wave may indeed, as with terminal T-wave inversion, signify spontaneous reperfusion.

A Negative U wave may also be found in patients with valvular heart disease, congenital heart disease, hyperthyroidism, and cardiomyopathies.

What are the implications of an increased amplitude positive U-wave in the precordial leads?

Prominent U waves (exceed 1 mm) can be seen in hypokalemia, early repolarization, bradycardia, hypothermia, left ventricular enlargement, atrioventricular block, congenital long qt syndrome, left circumflex myocardial infarction.

Usually, U wave has the same polarity as the T wave. According to earlier findings discordance between T and U and concordant negative T and U wave can also predict hypertension or myocardial ischaemia. 

In the appropriate clinical context, an increase in U-wave amplitude in the precordial leads may raise suspicion of posterior ischemia (due to an RCA or LCX lesion).  This could be considered the mirror image of a negative U-wave.

Here is a very nice full text article on the U-wave:

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10. Girish MP, Gupta MD, Mukhopadhyay S, Yusuf J, Sunil Roy TN, Trehan V. U wave: an important noninvasive electrocardiographic diagnostic marker. Indian Pacing Electrophysiol J. 2005 Jan 1;5(1):63-5. PMID: 16943944
11.  Sovari AA, Farokhi F, Kocheril AG. Inverted U wave, a specific electrocardiographic sign of cardiac ischemia. Am J Emerg Med. 2007 Feb;25(2):235-7.
12.  Pérez Riera AR, Ferreira C, Filho CF, Ferreira M, Meneghini A, Uchida AH, Schapachnik E, Dubner S, Zhang L. The enigmatic sixth wave of the electrocardiogram: the U wave. Cardiol J. 2008;15(5):408-21. Review. PMID: 18810715
13. Borbás J, Hategan L, Környei L, Katona M, Csányi B, Tringer Annamária, Forster T, Sepp R. Qualitative and quantitative assessement of ECG characteristics in patients with Andersen-Tawil syndrome. Scientific Congress of Hungarian Society of Cardiology - Cardiologia Hungarica, 2016.


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