Friday, September 28, 2012

Three Cases of Unstable Angina

Unstable angina consists of anginal symptoms but without a diagnostic rise and/or fall of troponin with one level above the 99% reference value for the assay used.  It may have ECG findings, or not.  Most "unstable angina" is diagnosed in patients who present to the ED with chest pain, or other symptoms suggestive of ischemia, but without a diagnostic ECG and without positive troponins.

After "ruling out for MI," the patient is then "risk stratified" with provocative testing (stress echo or stress sestamibi) or with CT coronary angiogram.  However, these are tests of stenosis and do not answer the question "Were the symptoms caused by fissuring and thrombosis of coronary plaque?"  In other words, they may answer the question of whether the patient has coronary disease, but not whether that disease caused the symptoms, and thus not whether the patient truly had unstable angina.  Stable coronary lesions (stenoses) are much less likely to cause subsequent infarction compared to unstable ones.  Evidence of truly unstable angina can be found in the ECG, or even in a rise and fall of troponins that is beneath the 99% reference value.

Patients who are at low risk for coronary disease, have low risk symptoms, have a truly low risk ECG (and this is where ECG expertise really comes into play), and serial undetectable troponins (or detectable but with no rise and fall), have an unknown benefit from such risk stratification testing.  (There have been no randomized trials showing benefit.)

The following cases of true unstable angina are very instructive:

1. This case is frightening 

2. In this case, the warning signs are missed and the patient returns with a STEMI

3. In this case, Wellens' T-waves are missed.

Wednesday, September 26, 2012

Acute Dyspnea in a Middle Aged Male

A middle aged man with several CAD risk factors presented with one week of intermittent  shortness of breath and then sudden severe SOB.  There was no chest pain.

Here is the initial ECG:

There is grouped beating, which should always make you think of Wenckebach (2nd degree, Mobitz type I).  This is indeed Wenckebach, which is common in inferior MI.  The rhythm itself is stable -- there is little danger of progression to complete AV block.  It is a sign that pathology is present, and this is confirmed with the ST elevation (< 1 mm in inferior leads and reciprocal ST depression in aVL).  There is also ST depression in V2 and V3, diagnostic of simultaneous posterior STEMI.  There is T-wave inversion which suggests reperfusion.  There is a pathologic Q-wave already in lead III.

The patient went for immediate angiography and PCI of a 100% occluded RCA.  Why was there T-wave inversion if the artery was 100% occluded?   Because there was good collateral circulation

Wellens' first described the T-wave inversion bearing his name in 1982 and it was in connection with "unstable angina" of the LAD, with stenosis in all cases progressing to complete infarction within a couple weeks.  In 1989, he published a much larger case series of 180 cases (out of 1260 consecutive cases of unstable angina), and 33 of these had 100% occluded arteries (the other 147 had open arteries).  But in all 33 cases, there was good collateral circulation.  The ECG tells you what is going on at the cellular level (ischemia or not), but not why there is or is not ischemia.  So whether the myocardium under those leads is reperfused through collaterals or through opening of the artery (spontaneous or due to therapy), there may be T-wave inversion. 

By the way, completed transmural infarction that has no reperfusion at all will also present with (shallow) T-wave inversion, but in the presence of well-formed, deep Q-waves.  Wellens' waves do not have pathologic Q-waves.

The initial troponin I was 14.1, indicating recurrent or prolonged MI.  TnI peaked at 28 ng/ml.

Echo showed EF of 53% and an inferior wall motion abnormality.

Saturday, September 15, 2012

Prehospital Ventricular Fibrillation in a Young Woman. What is the Diagnosis?

An under 30 yo woman collapsed and was found in ventricular fibrillation, and was successfully defibrillated.

Here is her prehospital ECG:
What is it?

ECG diagnosis: There is sinus rhythm.  There is what I call a "wavy" pattern and large U-waves (see arrow).  Do not mistake the U-wave for a T-wave, or the long Q-U interval for a long QT.  This is diagnostic of hypokalemia.  The K was 1.3 mEq/L.The patient eventually recovered.

Here are more ECGs of hypokalemia which demonstrate the "wavy" pattern:

Notice the "wavy" pattern in V2 and V3, created by downsloping ST depression followed by the U-wave. 

When there is an apparent T-wave with an apparent "down-up" pattern (in contrast to an up-down pattern, as in Wellens'), the terminal "up" portion is almost always NOT a T-wave, but rather a U-wave.  There is one exception to this: when the down-up is actually reciprocal to an up-down: this happens with Wellenesque T-waves in opposite leads aVL and III: Wellenesque up-down T-wave in lead III, indicative of inferior Wellens' waves (and thus inferior Non-STEMI), will have a reciprocal down-up in lead aVL and vice versa.

Here is another:
K = 1.4.  Notice again the wavy pattern in almost all leads, with down-up. The end of each wave is the (upright) U-wave.

K = 2.3.  Again, the wavy pattern.

Here are more cases of hypokalemia, some of which mimic ischemia. 

Tuesday, September 4, 2012

Male in his 40's with chest pressure: what is the diagnosis

This 40-some year old patient complained of chest pressure and had this ECG recorded:

See comments and diagnosis below

The providers were a bit worried about this ST elevation and I was in the department, so they showed it to me: my answer took 2 seconds and was unequivocal: LVH and early repolarization, no STEMI.

How did I know this?  Primarily because:

If inferior MI, there would be significant ST depression in aVL.
If anterior MI, there would not be such high voltage, especially in lead V4.

Though the early repol/anterior STEMI formula may give false positives in LVH (I'm actually not sure of this), the value obtained after plugging in STE60V3 = 5 mm, QTc = 400 ms, and R wave V4 = 33 mm = 18.2 (far less than 23.4, strongly arguing against anterior STEMI).  I did not use the formula, but one could do so and be reassured.

My colleagues appropriately did a bedside ultrasound and found completely normal function.  They did admit him for "rule out" and all troponins were negative.

Diagnosis: Anterior and "inferior" ST elevation due to LVH and early repolarization

Modified Sgarbossa Rule Published Online: Annals of Emergency Medicine

Link: Diagnosis of ST-Elevation Myocardial Infarction in the Presence of Left Bundle Branch Block With the ST-Elevation to S-Wave Ratio in a Modified Sgarbossa Rule

There are differences between previous posts and the findings in this paper.  

Previously, the best ratio was 0.20.  Due to slight differences in methodology, the final rule uses 0.25.  It is important to realized that the use of 0.20 will result in slightly higher sensitivity and lower specificity for STEMI. 

Also, I did not use the absolute value of the ratio.  Thus, whereas, before, excessive discordance was greater than 0.20, it is now less than -0.25 (less than a negative number).  This may be confusing, but was more accurate in terms of simple arithmetic (dividing a positive number by a negative one).

Thus, for the revised rule, the third component of the rule [greater than or equal to 5 mm discordant ST elevation in leads with a negative QRS (S-wave)] is replaced by a ratio of ST elevation at the J-point, relative to the PR interval (a positive number), divided by the preceding S-wave (a negative number, so the result is a negative number) that is less than or equal to -0.25, was far more sensitive and was more accurate than the Sgarbossa rule at diagnosing coronary occlusion.  Additionally, the discordant ST elevation must be at least 1 mm.  The criteria need to be met in only one lead to be positive.

Furthermore, we found that a simple rule using only any excessive discordance (excessively discordant ST elevation or ST depression in just one lead, without paying attention to concordance), with a ratio less than or equal to -0.30, was the most sensitive (100%), with excellent specificity (88%) and the best accuracy.

Both rules need validation in another study.  We are working on that.

The full text is not free now; I'm not sure if it will be when published in print.

Here are some example cases.

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