The term "Reciprocal Change"

[pchangb]

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I have two questions.

Question 1 :
Reciprocal change is
A) a phenomenon that can exclusively be seen in myocardial infarction(or some
other heart disease).
B) a general electrophysiologic law which asserts 'the opposite lead tends to show
inverted voltage'. We often apply the law when discussing myocardial infarction
with ST segement.

Question 2 :
If there is a transmural infarction in posterior myocardium, then ST depression
will be seen in v1~v4, by reciprocal change. Also if there is a subendocardial
infarction in anterior myocardium, then ST depression will be seen in v1~v4. How
can I differentiate them by EKG ?

😕

 

[MD2b06]

Look at the t wave. If it's anterior ischemia, the t wave will be inverted in the anterior leads. If it's a posterior MI, the ST segments will be depressed anteriorly, but the t-wave will be upright. You can also ask for posterior leads, v7, v8, v9.

 

[pchangb]

I am not satisfied fully, but thank you!

 

[Packman2003]

Look for an prominent R wave in V1. If You see one, think posterior. In anterior MIs you will see Q waves form rather than prominent Rs.

 

[drstar842]

I'm going to assume you will have ruled /in/out arrhythmias, bundle branch blocks, ventricular hypertrophies, Printzmetal's, or J point elevations before applying these steps. Also, all bets are off if WPW or LBBB is present

Reciprocal change refers to deviation of the ST segment, T wave, or Q waves in the opposite direction from that of their MAXIMAL deviation.
Easiest way to not get confused anymore:
1. Check V1-V2 for abnormal R wave (V1: R amp > S amp, R dur >= 0.04s, R amp >= 0.60 mV; V2: R amp >= 1.5 x S amp, R dur >= 0.05s, R amp >= 1.50 mV) and ST segment depressions (Just eyeball it, if their is a R wave present that's bigger than the S wave, you're probably dealing with posterior)
2. If you don't see those findings on the ECG then you can rule out a transmural posterior MI
3. If you ruled out a transmural posterior MI, then you don't need to worry about reciprocals anymore, as it's the only time "reciprocals" are used for a dx on ECG (and, even then, you need to get posterior leads before moving to additional testing). In other words, scan the ECG for ST elevations first. Then, if you find any, you can see if there are any reciprocal changes, though just b/c they aren't there doesn't mean it's not still a STEMI
4. If you don't see any STEMIs, and you ruled out the transmural posterior MI, then you are left w/ either subendocardial infarctions, subendocardial ischemia, and/or transmural ischemia. Remember, subendocardial infarctions by definition can't cause ST elevations and the damage they cause aren't typically extensive enough to cause any reciprocal changes either way (basically, don't start w/ a ST depression and look for its reciprocal ST elevation, do it they other way around)
5. Now, without cardiac enzymes or a timeline, it's difficult to separate these out. With an ischemic attack, the ST segment should return to baseline after the angina. While with non-Q-wave subendo infarction, the ST segment can stay depressed for up to 48 hrs (and you need positive cardiac enzymes). But, there are some tricks to try an localize the ischemia and differentiate transmural vs subendocardial:
LAD localized ischemia --> T wave inversions in V2, V3, V4
RCA localized ischemia --> T wave inversions in III & aVF (inferior) or V2 & V3 (anterior)
LCX localized ischemia --> T wave inversions in I, aVL, V4, V5, V6
For subendocardial ischemia, the MEAN direction of the T wave shifts AWAY from the involved ventricle
For transmural ischemia, the MEAN direction of the T wave shift TOWARDS the involved ventricle (may see hyperacute T waves with increased amplitude)

 

[pchangb]

Thank you.
R/O posterior STEMI -> R/O other STEMI -> other conditions. what a nice approach!