MI without 12 lead changes?

[DwayneEMTP]

Hey all,

Had a run the other night during my phase one clinicals.

50is male.

AAOx4, somewhat anxious, but in good humor.

Chest pain x 1-1.5 hours, radiating to neck and left arm, "pressure" in nature.

Nondiaphoretic, possibly a little pale, though not dramatically so. Skin warm and dry.

3 lead shows normal sinus rhythm @ 74

BP 125/85 (ish), pulse full and regular, Temp normal to touch.

Patient states stent placement x 2 at unknown locations x 3 years.

History of like pain level and location but no MI history.

Only meds ASA q a.m., nitro prn.

Pt states that pain was 6/10 before he self administered his prescribed nitro s/l 40 mins passed, then 4/10. A second dose 15 mins pre EMS showed no change in pain level. Pt denies n/v, LOC, other symptoms. Addl dose of nitro via EMS shows pain level change to 2/10.

12 lead shows normal sinus @ 68bpm without ectopy of any kind. I mean, it looked like the examples they give you on your first day of cardiology...Perfect.

Other interventions performed but unrelated to the question (I believe)

My question is this. After the call the medic asked me what I thought was going on. I said "I'm not sure, but it doesn't appear to be an MI."

She said "Ok, why?"

I said "The perfect 12 lead, nondiaphoretic, - n/v, but mostly because of the 12 lead."

In short she said (paraphrased) "I believe he was having an MI and it just hasn't shown up on he 12 lead yet, you do know and MI doesn't necessarily show up right?"

Well, I didn't..How can this be? If an EKG shows the electrical activity of the heart, and an MI changes that electrical activity, how can we have those changes without seeing it on the monitor?

Maybe a dumb question, but I don't get it.

Thanks for any help you can give!

Dwayne

[EMS49393]

The instructor responsible for my education taught that a 12-lead ECG would show a ST elevation in a person having an MI only 50% of the time. With a 15-lead, that increases to 73%. I value this statement to be pretty accurate, given I was a student of Bob Page.

Cardiac enzymes are reliable, however the 100% gold standard for detection, and hopeful correction of the acute MI is cardiac cath. Again, same instructor.

Sounds like a case of that patient not getting the memo on making sure his signs and symptoms were textbook. Sometimes they just aren't diaphoretic, they aren't nauseous, they have no changes on the ECG. Sometimes they have a toothache and syncope with changes on the ECG. Patients are all so strangely different.

[mobey]

There will be more in-depth answers than this but for now...

I think what she was refering to was a Non-STEMI, or Non-ST elevation MI. You may see inverted T waves or ST-depression in the absence of ST elevation or BBB.

The Non-STEMI is detected through elevation in cardiac enzymes like troponin.

If this scenario repeates itself reply to your medic "Might be a Non-STEMI, but I can only call it unstable angina till the blood work comes back".

I will be interested to see if there is really a delay in 12 lead changes in AMI, it would surprise me since ischemia causes ST depression, by the time an infarct ocurrs I would think you would see some sort of changes.

Thanks for the post, lookin forward to the replies.

Mobey

[Kaisu]

sounds like unstable angina that was on its way to an MI. Sometimes, they have no ECG or enzyme abnormalities at all. If angina doesn't resolve with nitro, we bring them into the hospital. If they have normal ECG/enzymes they are admited to the CDTU (cardiac diagnostic testing unit). Tests are repeated here for 12-18 hours. Often, the changes will reflect at that time. If all is normal, then we send them to the big belt sander (stress test). Anytime we pinpoint an MI, they go directly to the cath lab.

So yes - it is normal for a patient to be having an MI with no changes in enzymes or ECG.

[Doczilla]

Only 30-50% of acute MIs show EKG changes. EKG is good to "rule in" or confirm the suspected diagnosis, but is notoriously insensitive. You need cardiac enzymes and a stress test to rule it out.

'zilla

[AZCEP]

Only 30-50% of acute MIs show EKG changes. EKG is good to "rule in" or confirm the suspected diagnosis, but is notoriously insensitive. You need cardiac enzymes and a stress test to rule it out.

'zilla

Or, you could just take them to the cath lab to be sure On a serious note, Doc have you had any experience using ultrasound or CT/MRI for suspected MI's? Some of our docs have suggested they should be considered.

[DwayneEMTP]

Only 30-50% of acute MIs show EKG changes. EKG is good to "rule in" or confirm the suspected diagnosis, but is notoriously insensitive. You need cardiac enzymes and a stress test to rule it out.

'zilla

Yikes, don't I feel like a dope! I was pretty sure I stayed awake through all of cardiology, but somehow I missed this...

Thanks all, I'll do some review!

Dwayne

[Kaisu]

My instructor explained it as this : It takes about 1 hour for cardiac muscle to be injured and 6 for it to die. Often, there hasn't been enough damage until later for it to show up. I'm sure there are more technical answers but that one makes sense to me.

[Ridryder 911]

Hence the reason we perform "serial" ECG's. As well, ever seen non "q" wave AMI's? In fact one of the old test questions from ACLS was " a normal XII lead, excludes an AMI?"..

Like Doc described not all AMI's have ECG changes.

R/r 911

[akroeze]

My instructor quoted it as roughly 80% of MIs have XII Lead changes. I guess like anything else it depends on which study you quote.