Friday, October 26, 2012

Man in his 70's with presyncope. Some interesting data on troponins included.

Announcement: On Thursday, November 29 at 1:30 PM Central Time, there will be a live broadcast of the ECG Blog.  We will have a Skype call in number for your ECG questions.  Number to be announced -- see upper sidebar.

Case:

A man in his 70's presented with presyncope.  He denied CP or SOB.  He had no medical problems and had not seen a doctor in a long time.

Here is his initial ECG:
Sinus rhythm.  There is high voltage, possible LVH.  There is abnormal ST segment depression (STD) in leads II and aVF and V3-V6, with minimal ST elevation in aVR.  This is very suggestive of ischemia.

The patient remained asymptomatic in the ED.

At 26 minutes, another ECG was recorded:

There is slightly less STD here
Another ECG was recorded at 2 hours:
The ST depression is almost completely resolved.

So there is subtle, but real, and dynamic ST depression.  ST depression can be either secondary to an abnormal QRS (such as in LVH or LBBB).  Or it can be "primary", that is, not due to the abnormal QRS.  In this case it appears to be primary.

Such primary ST depression can be due to a baseline finding, in which case it is not dynamic.  It can be due to hypokalemia, but this patient was not hypokalemic.  Or it can be due digoxin, but this patient was not on digoxin.  Therefore, one must presume it is due to ischemia.  And, in such a patient, ischemia is probably due to ACS.

The patient was given aspirin and clopidogrel.  He was admitted.  His every 3 hour troponins [Ortho Clinical Diagnostics (OCD), level of detection = 0.012 ng/ml, manufacturer's 99% reference = 0.034 ng/ml] were: 0.014, then 0.020, then 0.017, then 0.012.  One last one measured a couple days later was less than 0.012 (undetectable).

So the troponins do not reach the level for diagnosis of NonSTEMI (which would require the troponin to reach 0.035 ng/ml).  But there is a rise and fall.  This, especially along with the EKG findings, is diagnostic of unstable angina.

Some data on troponins:

The manufacturer's 99% reference level is determined by testing a heterogeneous population of people, some with chronic diseases, and in the case of this OCD assay, 99% have a level less than or equal to 0.034.  Recently, Apple et al. (Clinical Chemistry 58(11): xxx-xxx; 2012; http://hwmaint.clinchem.org/cgi/doi/10.1373/clinchem.2012.192716) studied troponin levels in over 500 truly normal individuals and found that the 99% reference for the OCD assay is 0.019 ng/ml.  So if the definition of MI were based on this, rather than the manufacturer's level, one could call this an MI.

Here are 3 articles suggesting that, with high sensitivity troponin, many cases of angina are detectable, and that they have a rise and fall beneath the 99% reference for MI:


1.            Januzzi JL, Jr., Bamberg F, Lee H, et al. High-sensitivity troponin T concentrations in acute chest pain patients evaluated with cardiac computed tomography. Circulation 2010;121(10):1227-34.
2.            Sabatine MS, Morrow DA, de Lemos JA, Jarolim P, Braunwald E. Detection of acute changes in circulating troponin in the setting of transient stress test-induced myocardial ischaemia using an ultrasensitive assay: results from TIMI 35. Eur Heart J 2009;30(2):162-9.
3.            Venge P, Johnston N, Lindahl B, James S. Normal plasma levels of cardiac troponin I measured by the high-sensitivity cardiac troponin I access prototype assay and the impact on the diagnosis of myocardial ischemia. J Am Coll Cardiol 2009;54(13):1165-72.


In any case, the rise and fall of  troponin, whether above or below the 99% reference, repesents ACS.  It is important to note, however, that in ACS, the lower the troponin level, the lower the risk.  Nevertheless, a rise and fall like this, even if below the level for diagnosis of MI, indicates ACS and puts the patient at risk of a larger MI and even death.

Outcome

The patient was in the hospital for several days.  He had some episodes of what is described as variously as bundle branch block and as ventricular tachycardia.  He had a normal echocardiogram, and a normal stress test EXCEPT that he had runs of V Tach during the test.

An angiogram showed a 90% RCA stensosis.  He received a stent.

Conclusion:

1. The patient had unstable angina, but without pain.
2. Dynamic ST depression is nearly diagnostic of ischemia
3. Rise and fall of troponins, even if too low to diagnose MI, indicates ischemia and, in the this clinical context, unstable angina.

3 comments:

  1. Very useful post, thank you, and I'm looking forward to the 29th!

    Also, you mentioned that the 99% reference in the Apple et al. paper was shown to be 19 ng/mL, but I believe you meant 19 ng/L.

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  2. I had been learned that if there is reciprocal changes, it indicates myocardial injury? am I right, sir...

    In the ECG shown, no reciprocal changes i can find..(ST depression at III should be ST elevation in aVL

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