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Isolated Posterior Wall M.I.

Submitted by Dawn on Sat, 11/11/2023 - 15:51

This interesting case was provided by Dr. Bojana Uzelac, Emergency Medicine physician.  We are paraphrasing a translation of her comments here.

The patient is a 50-year-old complaining of chest pain.

The ECG shows a rare occurrence – an isolated POSTERIOR WALL MI (PWMI).  Note that leads V1 through V4 show the usual signs of posterior wall MI.  We see ST segment depression, which represents a reciprocal view of the ST elevation present on the posterior wall of the left ventricle.  The relatively tall, wide R waves in V2 and possibly V3 represent pathological Q waves on the posterior wall. (V2 R/S ratio > 1). What is unusual here is that there are no signs of inferior wall MI or lateral wall MI.  Posterior wall MI usually occurs in conjunction with one of these.

 PWMI is most often seen as an extension of inferior wall MI or lateral wall MI, because of shared blood supply.  Usually, it is the right coronary artery that supplies both the posterior and inferior areas of the left ventricle (about 80% - 85% of the population).  In some individuals, the circumflex artery supplies both areas. Posterior M.I. may also be seen in conjunction with lateral wall MI, when the circumflex supplies the posterior and lateral walls.  In the case shown here, only the posterior wall is involved.  Most cases of isolated PWMI involve either the circumflex or one of its marginal (OM) branches.  Only about 3.3% - 5% of all MIs are isolated PWMI.

 

Dawn's picture

Inferior Posterior Wall M.I. In Cabrera Format

Submitted by Dawn on Sat, 08/26/2023 - 16:53

Does something about this ECG look "different" to you?    This ECG shows a “classic” presentation of inferior-posterior M.I. when it is caused by a lesion in the right coronary artery (RCA). There are ST elevations in leads II, III, and aVF.  Reciprocal ST depression is seen in Leads I and aVL.  There is also reciprocal ST depression in Leads V1 – V3.  These more rightward anterior leads are reciprocal to the posterior (or posterior-lateral) wall, so the ST elevation is actually posterior.  Another sign that this is an RCA lesion is that the ST elevation in Lead III looks worse than the STE in Lead II.  It would be helpful to check the right precordial leads, or at least V4 Right, as elevation there would indicate right ventricular M.I. 

Depending on how experienced you are at evaluating ECGs, you might have immediately noticed something “different” about this tracing.  It is printed in Cabrera format, which groups the leads (viewpoints) more geographically than a traditional ECG does.  In addition to grouping the leads more geographically, instead of aVR, the machine records - aVR.  That reverses the negative and positive poles of aVR, putting the positive ("seeking") electrode at 30 degrees - halfway between Leads I and II.   Those of us who have been looking at ECGs for decades often feel a bit disconcerted by this format, because we have developed almost an intuitive way of seeing the ECG as a “map”, and this rearrangement thwarts our brains’ approach to the ECG.  I would imagine, however, that this might make interpretation a bit easier for someone who is not prejudiced by the standard way of printing.  This method is especially helpful when looking for inferior wall M.I., as we see here, because the lateral leads are together in a row, and the inferior leads are grouped together. 

Dawn's picture

Widespread ST Elevation With Right Bundle Branch Block

Submitted by Dawn on Sat, 02/04/2023 - 10:22

Usually, instructors of basic ECG classes look for examples of the most common conditions that are likely to be encountered by the learners.  But, sometimes, it is advantageous to show students more unusual presentations to remind them of the infinite possibilities when we care for living beings.  This series is a very good example of what can and does happen to some people with cardiovascular disease.  It will give your students an opportunity to think about possible interpretations, and also about anticipating clinical implications and emergencies that may arise.

The Patient:  This patient is a man in his 80s who has been active his whole life.  He considers himself to be healthy, giving no medical history and denying medication use. He states that he has had a yearly health exam.  Today, he felt “tired and dizzy” while raking leaves.  As he walked to his house to rest, he had a syncopal episode and fell, hitting his head. He was unconscious for a few minutes. A family member called for Emergency Medical Services (EMS). Paramedics found him awake and complaining of bilateral “shoulder and wrist” pain. He had no obvious trauma to his extremities, but had some bruising on his head and face.  He denied recent illness and substance abuse.  He was oriented x3. He was pale and diaphoretic, and complained of nausea. He denied chest or back pain.  He denied shortness of breath.  BP 100/60.  Heart rate bradycardic.  SPO2 above 95%.  He was given aspirin and ondasetron, and transported to a hospital.

Dawn's picture

Inferior-posterior Wall M.I. and AV Dissociation

Submitted by Dawn on Mon, 12/06/2021 - 17:59

At the ECG Guru website, our main goal is to provide quality teaching materials to those who teach ECG interpretation and other cardiac topics.  This ECG offers teaching opportunities for those who teach any level of student.

The patient:   This ECG was obtained in the Emergency Department from a 54-year-old man who was complaining of severe chest pain and nausea.  His BP was 130/68.

Dawn's picture

Inferior Wall M.I. With Atrial Fibrillation

Submitted by Dawn on Sat, 02/23/2019 - 22:17

The Patient   This ECG was obtained from a 74-year-old man who had a history of COPD. He was complaining of severe chest pain at the time of the ECG.

The ECG     The rhythm is atrial fib or flutter (the R to R intervals are irregular, but seem to repeat about 4 interals).  Flutter waves are seen during some of the longer intervals. The rate is approximately 90 beats per minute.  The ST segments are very noticeably elevated in Leads II, III, and aVF.  There is reciprocal ST depression in Leads I and aVL, and also in all the precordial leads. 

Dawn's picture

Inferior Wall M.I. and Right Bundle Branch Block

Submitted by Dawn on Wed, 09/06/2017 - 20:45

These ECGs were taken from a 76 year-old-man who was complaining of chest pressure for 20 minutes.  He had a remote history of coronary artery bypass graft surgery.

This case has several good teaching points, including:

Significant artifact.  The limb leads show artifact which is severe enough to hamper our assessment of the j point location. Every effort should be made to eliminate artifact.  Some measures that might help are:

        *  clean and slightly "rough up" the skin where the electrode will be placed.  A rough wash cloth or gauze pad will work.

        *  shave hair if necessary.

        *  avoid areas of movement if possible.  Precordial electrodes must be placed in specific spots, but limb leads may be placed anywhere on the limb or on the trunk if it is impossible to avoid movement on the limbs.

       *   use fresh electrodes that have been protected from drying out.

Subtle STEMI changes.   This patient has an inferior wall M.I., which was confirmed as a complete occlusion of the right coronary artery in the cath lab.  The ST elevation in Leads II, III, and aVF is subtle, and more difficult to measure because of the artifact.  However, the SHAPE of the ST segments is a giveaway - they are very straight.  A convex-upward shape is normal (see Lead I).  Also, Lead aVL shows typical ST DEPRESSION, as a reciprocal view of the STE in Lead III.  More ST depressions can be seen in Leads V1 through V3, and they end abruptly there.  These localized ST depressions represent a reciprocal view of the posterior (also called lateral) wall, and represent an "extension" of the inferior wall M.I. up the back of the heart.  A V4 Right lead was obtained and shows no measurable ST elevation, but the shape is straight to slightly "frowning", indicating that the right ventricle may soon have STE.  Repeat ECGs should be obtained to watch for more definite ST elevations.

Dawn's picture

Inferior-lateral and Posterior M.I.

Submitted by Dawn on Thu, 01/15/2015 - 23:55

This is from a Cardiac Alert patient, with chest pain, in the Emergency Department.  The ECG shows ST elevation in the inferior leads (II, III, and aVF), and in the low lateral leads (V5 and V6).  There is reciprocal depression in V1 and V2, indicating injury in the posterior wall.  One could argue that "inferior" is just the term we use for the lower part of the posterior wall - the part that faces the floor in a standing person.  So, "inferior-posterior" reflects a more proximal occlusion of the culprit artery.

The high lateral wall is represented by I and aVL.  These leads would usually show marked reciprocal ST depression when II, III, and aVF have elevation.  However, in this ECG, aVL is depressed, but not as much as expected, and Lead I almost looks elevated!  This could represent even more extensive lateral wall involvement.  A dominant right coronary artery could be the culprit, but it seems more likely that a dominant circumflex artery is to blame, as it could perfuse the entire lateral wall before joining with the posterior descending artery and perfusing the inferior wall.  Unfortunately, we do not have the cath results on this patient.

The ST elevation in this ECG has the classic appearance of acute M.I., and will be interesting to both beginner and advanced students.

Often, one ECG can provide a wealth of teaching opportunities, no matter what the level of your students.  For the student learning to monitor the rate and rhythm, you might crop this image to only show the Lead II rhythm strip at the bottom, for a good example of normal sinus rhythm with a borderline PRI of .20 sec.   For the student learning about ST elevation M.I., this is a good example of inferior-posterior and lateral injury.  Leads aVL, V1 and V2 demonstrate reciprocal ST depression.  When an observant student notices the slight ST elevation in V6, a discussion of coronary artery distribution can occur.  

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