This is the conclusion to 90 year old male CC: "Possible stroke". You might want to go back and familiarize yourself with the details of the case. Let's take another look at the 12-lead ECG.
Now with the computerized interpretive algorithm.
On Facebook I had asked whether or not this ECG showed signs of ischemia.
This ECG shows ST-depression in the lateral leads (I, aVL, V5 and V6) and modest ST-elevation in the right precordial leads (V1-V3). That's because it shows a strain pattern or secondary repolarization abormality due to left ventricular hypertrophy.
According to at least one study this is the most common cause of ST-elevation in chest pain patients. Hence, it is a very important pattern for paramedics to recognize in the field (although it's rare for LVH with strain to fool the GE-Marquette 12SL interpretive algorithm).
How would we know it's a strain pattern?
When we look at any 12-lead ECG we should consider the Six Step Method (or some other standardized approach).
Here we see that the patient is in sinus rhythm with a normal frontal plane axis. The QRS duration is < 120 ms so it's not a bundle branch block or paced rhythm.
At this point we might pick up on ST-depression in the lateral leads but it's too early to call it ischemia. We need to consider other possible causes. Since left ventricular hypertrophy often presents with ST-depression in the lateral leads that is a likely culprit.
Let's add the depth of the S-wave in lead V2 with the height of the R-wave in lead V5 (or V6 — they're both about the same). Is the result equal or greater than 35 mm?
You don't need calipers for this because it doesn't have to be perfect. 35 mm is 7 large blocks so eye-ball it. The S-wave in lead V2 is at least 4 large blocks deep (it's actually more than 5 but this is the "fast and dirty" method) and the R-wave in lead V6 is at least 3 large blocks in amplitude. That's greater than 35 mm so you've met the criteria.
There are other criteria for LVH but this is the most important for ruling out STEMI mimics because LVH is usually an anterior STEMI mimic so the most important issue here is the depth of the S-waves in the right precordial leads (V1-V3). With a "strain pattern" the deeper the S-waves the more pronounced the secondary ST-T abnormality in the opposite direction.
Conversely, the taller the R-waves, the more pronounced the ST-depression and T-wave inversion. A lot of people talk about the shape of the ST-segments and T-waves in the presence of LVH, how it should be asymmetrical and upwardly or downwardly concave. That's ususally true but it's not always the case.
In this case the "strain pattern" is fairly modest. The ST-elevation in V1-V3 is not particularly impressive. Other times the result can be quite profound.
If you're still not clear on what a "strain pattern" is with LVH, take a look at the precordial leads. The QRS complex starts out negative in lead V1 and ends up positive in lead V6. The transition lead is lead V4 (which is equiphastic). As the QRS complex transitions from negative to positive, the T-wave transitions from positive to negative.
That's what we call a "widened QRS/T angle" which means that there is more than 100 degrees difference between the QRS axis and the T-wave axis. Let's take a look at the computerized measurements. The QRS axis is 16 degrees and the T-wave axis is 148 degrees.
To be much simpler about it, with a strain pattern positive QRS complexes have negative T-waves and negative QRS complexes have upright T-waves. (You should not include isoelectric or equiphasic QRS complexes in this analysis).
The general appearance of this 12-lead ECG is one of T-wave discordance. That's a finding that should almost always make you pause and consider that you're dealing with a secondary ST-T abnormality — in other words a STEMI mimic.
This patient received a fairly extensive workup for his near-syncope including a CT scan and nothing was found. He was discharged from the emergency department.
You can find previous posts about left ventricular hypertrophy here.
The Code STEMI Web Series comes to First Responders Network!