Chest pain and LBBB. LBBB resolves and there is V1-V3 T-wave inversion.

A 59 year old man with no cardiac history was at work when he developed very typical substernal chest pressure.  He went to a clinic across the street and had this ECG recorded:

There is sinus tach with LBBB with appropriate discordance and no excessive discordance.  

To learn about appropriate and excessive discordance, please see this post:
http://hqmeded-ecg.blogspot.com/2011/05/lbbb-is-there-stemi.html


911 was called, the medics arrived, and recorded this ECG:

Again, there is sinus tach and no concordant ST elevation, all ST segments are appropriately discordant.  There is lead misplacement: the axis is different and all of I, aVL, V5, V6 should have upright R-waves; the fact that they are negative in I and aVL confirms lead misplacement.  The S-waves are not very deep, but that is because they are cut off.  If projected, they are indeed very deep.

The patient arrived in the ED and had this ECG:

No difference.  Sinus tach with appropriate ST segments.

The following ECG was recorded later:

Now the heart rate is 72 and LBBB is gone.  There is, however, T-wave inversion in leads V1-V3, suggestive of Wellens' syndrome.

Is this an anterior STEMI with LBBB?  Did the occlusion reperfuse, resolving the LBBB and leaving the patient with reperfusion T-waves (Wellens' syndrome)?

He was taken to the cath lab.  All coronaries were completely normal.  All troponins were undetectable.

Explanation:
The patient had a worrisome history: 59 yo with significant substernal chest pressure, so his pretest probability of MI (and even of STEMI) is reasonably high.  However, he had a left bundle brach block with normal appropriate discordance on 3 EKGs.  Only 5-13% of patients with chest pain and LBBB have MI; many fewer have coronary occlusion.  Additionally, appropriate discordance is common in NonSTEMI, but very unusual in coronary occlusion (STEMI).   

Moreover, and importantly, there was sinus tach.  Whenever you see tachycardia with bundle branch block, you should suspect that it is rate related BBB.  Indeed, once the heart rate came down, the BBB resolved.

After resolution, there was T-wave inversion in V1-V3, highly suggestive of ischemia.  There are features of the T-wave inversion, however, which argue against ischemia.  First, as I have pointed out in posts on pulmonary embolism (see links), T-wave inversion of anterior infarction (Wellens' syndrome) almost always has an upright T-wave in lead III.  Also, anterior ischemia is unlikely to spare lead V4 as in this case.
http://hqmeded-ecg.blogspot.com/2011/03/chest-pain-sob-anterior-t-wave.html
http://hqmeded-ecg.blogspot.com/2010/03/anterior-t-wave-inversion-due-to.html

Cardiac Memory
There is another more likely explanation of this T-wave inversion: "Cardiac Memory."  Cardiac Memory (CM) has been described for a couple decades.  It is most common after termination of pacing and other etiologies of abnormal depolarization such as Left Bundle Branch Block.  After resolution of the abnormal depolarization, there may be transiently inverted T-waves that last for hours to days (these T-waves are the heart's "memory" of the previous abnormal conduction).  This phenomenon is poorly understood, but involves "transient electrical remodeling." 
http://www.heartrhythmjournal.com/article/S1547-5271%2807%2900801-6/abstract

Shvilkin et al. described the way to differentiate CM from ischemia:
http://circ.ahajournals.org/cgi/content/full/111/8/969
In short, the combination of:
(1) positive T_aVL (as in this case) and
(2) positive or isoelectric T-wave in lead I (as in this case) and
(3) maximal precordial T-wave inversion greater than the T-wave inversion in lead III (as here: maximal precordial T inversion is in lead V2, at 4.5 mm, and T-wave inversion in lead III is only 2.5 mm) was

92% sensitive and 100% specific for CM, discriminating it from ischemic precordial T-Wave Inversion.

Thus, the very well informed physician could differentiate these ECGs from those of an LBBB patient with MI:
1) no concordance
2) no excessive discordance
3) LBBB with tachycardia, probably rate related
4) subsequent T wave inversion that, according to Shvilkin et al., is diagnostic of cardiac memory.  It is NOT Wellens' syndrome.