Acute M.I.

This ECG was taken from a 66-year-old woman who presented to the emergency department complaining of chest pain and shortness of breath.  She attributed her symptoms to her COPD, but stated that her aerosol treatment had not helped.  She waited for some time before deciding to go to the hospital, then drove herself. In the emergency department, she had blood drawn, an I.V. started, and an aerosol treatment of albuterol.  She was then taken to the radiology dept. for a chest xray.  When she returned, a 12-lead ECG was done.  45 minutes had passed since she first arrived at the hospital.  This ECG is shown here.  It shows ST elevation in the inferior leads:  II, III, and aVF.  The patient was taken immediately to the cath lab, where her right coronary artery was found to have a 100% occlusion. (See image accompanying this ECG).  Angioplasty was successful, and stents were placed in the artery.  The patient was found to have anemia, with a hemoglobin of 5.5, and she was given a blood transfusion.  During the cath procedure, a ventriculogram was performed, which showed a stunned and akinetic inferior wall.  Unfortunately, subsequent ventriculogram performed several weeks later showed the lack of motion of the inferior wall to be permanent.  The ventriculogram is also posted here, and at this YouTube link, so you will be able to show your students the mechanical effects on the heart of a delay to treatment in acute STEMI.  See our YouTube site for more ventriculograms and cath videos.

Unbelievably, this inferolateral ST elevation M.I. was missed by the treating paramedics in the field.  An elderly woman stepped off a curb and was hit by a very slow-moving car.  She fell and sustained a Colle's fracture of the right wrist. While the paramedics assessed her, she complained of chest pain, prompting them to perform a 12-Lead ECG.  The machine's interpretation called attention to the inferior and lateral walls' injury pattern, but the paramedics did not believe it, because "she was a trauma patient". They ran three ECGs, and still did not agree with the machine.

The patient was transported to a hospital without an interventional cath lab, and she was forced to endure a one-hour wait to be transferred to an appropriate hospital.

This is a great ECG for a discussion with your students about "distractors".  The call came in as a trauma, so that, in itself, was a distractor.  The rescuers saw what they expected to see. The angulated fracture distracted them - putting them into full trauma assessment mode.  Then, the frequent and coupled PVCs also distracted them, possibly making it more difficult for them to evaluate the ST segments in the normal beats.  Interestingly, the second and third ECGs did not have PVCs, and the ST elevation was even more clear.

PVCs which are repeating themselves in groups of two, three, or more are sinister in a chest pain patient, and may indicate LV dysfunction. They could possibly result in ventricular tachycardia, which would be disasterous for this patient.

In this ECG, there is ST elevation in II, III, and aVF and reciprocal ST depression in I and aVL, indicating acute inferior wall M.I. Also, this patient has developed pathological Q waves in III and aVF, and probably II as well, indicating permanent damage to the myocardium.  A ventriculogram or echocardiogram will confirm akinesis of the inferior wall in most cases.  In this ECG, there is no ST depression in V1 through V3, so we can hope the posterior wall has been spared.  Notice the flattening of the ST segments in the elevated leads.  This is a sign of CAD.  Last week's ECG had coved upward (frowning) ST segments, which are even more sinister looking.  Lead V1 has the flattening, and a pathological Q wave.  When V1 looks "sick" and V2 looks "well", there is a good probability of right ventricular injury as well.  Lead III has a taller ST segment than Lead II.  This has also been shown to be a marker of RVMI.  Regardless, a right-sided ECG, or at least a V4 right, should be obtained in any IWMI, since the RCA often supplies both the right ventricle and the inferior wall of the left ventricle.

The rhythm in this ECG is interesting, as well.  It appears to be sinus, but it is difficult to evaluate P waves.  In the Lead II rhythm strip, they appear to change in morphology. Because the R to R interval remains constant, we feel this change in appearance is due to baseline artifact caused most likely by patient movement such as breathing.  What do you think?  

Our thanks to Andrew Porter for contributing this ECG.