Inferior Wall 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.

This week's ECG of the Week is from an elderly woman who suffered an acute occlusion of the right coronary artery.  The ECG clearly shows ST elevation in leads II, III, and aVF, indicating inferior wall injury.  In this case, this ECG was obtained in the field by paramedics, and was the second ECG done on this patient. For this tracing, the paramedics obtained V3 and V4 on the right side to better view the right ventricle. V3 and V4 right clearly show ST elevation as well, indicating RVMI.  The slight coving and elevation observable in V1 is also an indication of RV involvement, and the ST depression in V2 indicates posterior wall injury.  All of this results from a proximal lesion of the RCA in this patient.  Such a lesion carries a high morbidity and mortality.

Taking the time to obtain a right ventricular lead is controversial in some settings.  Some believe the patient's hemodynamic condition should be treated, regardless of the presence or absence of ST elevation in right chest leads.  Others find it very helpful to know that the right ventricle is affected.  In this case, paramedics in this community have a protocol to avoid the use of nitroglycerine in RVMI patients, even when the BP is adequate.  So, for them, it is important to have the information gathered from V Right leads.

The rhythm here is interesting, as well, and not at all uncommon for IWMI patients.  The baseline artifact makes it a bit difficult to march out all the P waves, but it appears they are sinus P waves that are slightly irregular at a rate of 52 to 54.  The PR intervals appear to be progressively prolonging, but there is no "grouped beating" observable on this short strip.  A lack of a concurrent Lead II rhythm strip also makes it difficult to determine the rhythm, as Lead II does have very visible P waves, and would be helpful.  The regularity of the narrow complex bradycardia points to a junctional escape rhythm, which would make this a third-degree AVB at the AV node level, which is very common with IWMI.  What do you think?

This month's strip from Jason Roediger's ECG Challenge blogpost is a nice complement to the strip presented here.  His is much clearer, and has a Lead II rhythm strip.  Do you think these ECGs show the same rhythm, or two different rhythms?

For an excellent discussion of "AV Dissociation" vs. "AV Block", go to Christopher Watford's Ask the Expert post.  Thanks very much to ECG Guru Sebastian Garay for this interesting ECG.

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.

Inferior wall MI: ST elevation in II, III, and aVF. Reciprocal ST depressions. Sinus bradycardia and first-degree AV block suggests sinus node and AV node ischemia. This is a good "classic" inferior wall M.I. It is good for teaching inferior-posterior injury, and the effects of RCA occlusion on the sinus and AV nodes. The low voltage in the limb leads may also be due to acute M.I., but in this case, we do not know the patient's body size.