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Inferior-lateral M.I. With QRS Fragmentation

Submitted by Dawn on Sat, 08/13/2016 - 23:33

SUBTLE ST CHANGES This ECG was obtained from an 87-year-old man who was experiencing chest pain. Due to the subtle ST elevation in Leads II, III, aVF, V₅, and V₆, (inferior- lateral walls) the ECG was transmitted to the hospital by the EMS crew, and the cath lab was activated. The patient denied previous cardiac history.

In addition to the subtle ST elevation, there is ST depression in V₁ through V₄, which represents a reciprocal view of the injury in the inferior-posterior-lateral wall. Because the anterior wall is superior in its position in the chest, it is opposite the inferior/posterior wall, and can show ST depression when the inferior-posterior area has ST elevation. This ECG was the 6^th one done during this EMS call. Prior to this one, the ST segments were elevated less than 1 mm. This is a good example of the value of repeat ECGs during an acute event.

RIGHT VENTRICULAR M.I.? This ECG was done with V₄ placed on the right side, to check for right ventricular M.I., which is a protocol for this EMS agency. When the right coronary artery is the culprit artery (about 80% of IWMIs), RVMI is likely. In RVMI, we would usually see reciprocal ST depression in Leads I and aVL, but the STE is very subtle here, so the depression would likely be also. When the culprit artery is the left circumflex artery (<20%), lateral lead ST elevation is more likely, as we see here in V₅ and V₆.

WHAT ABOUT RHYTHM? The rhythm is sinus with PACs. PACs are considered to be benign in most situations, but in a patient with acute M.I., any dysrhythmia can be concerning. The QT interval, measured as QTc (corrected to a heart rate of 60 bpm), is slightly prolonged at .458 seconds (458 ms). Over .440 seconds is considered prolonged in men, and over .500 sec. places the patient at increased risk of developing torsades de pointes. CAD and myocardial ischemia can lead to this modest increase in QTc.

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Atrial Fib To Cardiac Arrest

Submitted by Dawn on Sun, 07/03/2016 - 14:31

A paramedic crew responded to the office of a local physician. A 61-year-old male presented with a one-week history of chest pain and shortness of breath. He had a previously undiagnosed atrial fibrillation with rapid ventricular response and left bundle branch block, but was alert. Shortly after transport commenced, the patient became unresponsive with Torsades de Pointes, which rapidly degenerated into ventricular fibrillation. The paramedic placed pads and defibrillated within one minute. After two minutes of compressions, the patient had a fairly regular rhythm with return of spontaneous circulation. Transport time was short. On catheterization, the patient was found to have severe coronary artery disease, requiring coronary artery bypass graft surgery (CABG) A balloon pump was inserted in an attempt to strengthen him for surgery.

What is the rhythm? The 12-lead ECG presented here shows atrial fibrillation at a rate of 138 per minute. The rhythm is irregularly-irregular with no P waves. Since the patient had not yet been diagnosed with atrial fib, obviously no therapy had been initiated to control the rate. There is a PVC near the end of the strip.

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Inferior-posterior M.I. With Subtle ST Elevation

Submitted by Dawn on Mon, 01/18/2016 - 00:24

This ECG is a good example of an inferior wall M.I. that was confirmed and treated in the cath lab.

The ST segments are elevated in Leads II, III, and aVF, but the amount of elevation may look subtle to some. When the amount of elevation seems small, what other signs can help us recognize acute ST-elevation M.I.?

PATIENT HISTORY AND PRESENTATION This patient had acute chest pain, and was over the age of 50. We do not know his past medical history. His chest pain was described as substernal and epigastric, radiating to his back. He had nausea and diaphoresis. His past medical history is unknown, but it would be significant if he had a history of coronary artery disease, past M.I., smoking, metabolic syndrome, strong family history of heart disease, etc.

ST SEGMENT ELEVATION DISTRIBUTION In acute STEMI, the elevation will be seen in “related leads”. That is, the leads that are affected will reflect a region of the heart that is supplied by the same artery. Some M.I.s are larger than others, affecting more leads, because some obstructions are more proximal than others in the artery. This ECG shows STE in the inferior wall leads: II, III, and aVF. The culprit artery for this patient was the right coronary artery, which supplies the inferior and posterior wall of the left ventricle, the right ventricle, and the right atrium in the majority of people.

RECIPROCAL ST DEPRESSION Finding reciprocal ST depression in the leads that are OPPOSITE the affected leads is a very reliable sign to confirm that the STEs are due to an acute M.I. In fact, often the reciprocal depression is “stronger” or easier to see than the elevation. It is important to teach your students how the standard leads are oriented to the heart, so they will recognize the 12-Lead ECG as a “map” of the heart. The reciprocal ST depression in this ECG is seen in Leads aVL and I (subtle), which are across the frontal plane from Lead III. We also note reciprocal ST depression in the precordial leads, especially notable in Leads V1 through V3. This can reflect the injured area extending up the back of the heart from the inferior wall (posterior wall). The R waves in V2 and V3 are a bit higher than normally expected, which could indicate a reciprocal view of pathological Q waves on the posterior wall. Print the ECG out on paper, turn it upside down, and look at V2 and V3 through the back. V2 and V3 will look like a “classic” STEMI. This should be approximately the view you would get from additional posterior leads.

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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.