Persistent ST elevation after previous MI, otherwise known as "LV aneurysm" morphology
Posted Aug 27 2009 11:32pm
Case 1.Classic anterior LV aneurysm morphology (Persistent ST elevation after previous MI).
This 46 yo male presented with chest pain. There is 1 mm of ST elevation in V1-V3, but there are large QS-waves preceding the STE. Such QS waves are highly suggestive of old transmural MI, with subsequent akinesis or dyskinesis of the anterior wall. Acute MI, if early in its course (first 6 hours, at least), always has tall T-waves in addition to ST elevation.
There is one retrospective study (Smith SW. American Journal of Emergency Medicine 23(3):279-287, May 2005) showing that the T/QRS ratio is significantly greater in acute anterior STEMI than in old anterior MI with persistent ST Elevation. The best criterion for differentiating was the sum of STE in V1-V4 divided by the sum of the QRS's in V1-V4 (TV1+TV2+TV3+TV4 divided by QRSV1+QRSV2+QRSV3+QRSV4). If this value was <0.22,>0.36, then it is likely to be acute STEMI.
T-waves in aneurysm may be upright or inverted, but in neither case should they have high voltage. [Deep inversions suggest very recent NSTEMI (e.g., Wellens'). Tall T-waves suggest acute STEMI.]
The above ECG has a summed ratio of 0.05 and is clearly NOT an acute STEMI. It is important to know that only about 70%-80% of patients with the ECG morphology of "LV aneurysm" actually have an LV aneurysm, as defined by echocardiographic dyskinesis. "LV aneurysm" is far less common in this era of reperfusion, in which STEMI is not allowed to progress to full infarction (also known as "transmural" infarction, an old but useful term). The patient above had akinesis and had formerly had a mural thrombus, which is a common complication of an immobile wall which also may have post-infarction inflammation.
This patient ruled out for MI with negative troponins.
Case 2. Exaggeration of persistent STE after old MI by tachycardia
This 65 yo male presented with dyspnea but no CP. The lungs sound wet. The ECG is shown.
There is quite a bit of ST elevation in the anterior leads, but it is preceded by very deep QS waves suggestive of old MI. Previous MI can have persistent ST elevation, and just like in Left Bundle Branch block and other entities, ST elevation may be exaggerated in states of tachycardia. Therefore, the T-wave to QRS ratio may also be exaggerated. Here the formula TV1+TV2+TV3+TV4 divided by QRSV1+QRSV2+QRSV3+QRSV4 = 0.27, substantially > 0.22, and would indicate acute STEMI. But one must be suspicous of a false positive in the presence of extreme tachycardia such as this. Also arguing against STEMI is the fact that there is no single T/QRS ratio (V1-V4) > 0.36.
The difficult decision is this: is this an old MI with exaggerated persistent STE due to tachycardia, or is it an old MI with a new STEMI superimposed? Given that the BNP was > 5000 and the patient had no chest pain, and the high likelihood that such a morphology represented the former (not the latter) diagnosis, the patient was not set up for angiogram and reperfusion.
A previous ECG was found and is shown It is evident that there previously was classic LV aneurysm morphology, but with much less ST elevation. The ratio here is 0.05. A previous echo had shown severe decreased LVF with an akinetic anterior wall.
Clinicians correctly interpreted the first ECG as exaggeration of ST elevation of old MI due to tachycardia, stress, and exacerbation of CHF. Treatment of CHF resulted in a slowing heart rate. Follow up confirmed all troponins negative and resolution of ST elevation when the heart rate came down.