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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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Inferior Wall M.I.

Submitted by Dawn on Tue, 11/17/2015 - 14:38

This ECG shows a common manifestation with inferior wall M.I., BRADYCARDIA. We see the signs of acute inferior wall M.I. in the inferior leads: II, III, and aVF all have ST segment elevation. There almost appear to be pathological Q waves in Leads III and aVF. There are still VERY tiny r waves, and the downward deflections are not wide, but should full-blown Q waves develop in these leads, they would signify necrosis in the area. A repeat ECG would certainly be warranted.

Another sign that there is an inferior wall STEMI is the ST segment depression in Leads I and aVL, which are reciprocal to Lead III. ST depression can have many meanings, but when it is localized in the leads which are opposite ST elevation, it is reciprocal. There is also ST depression in Leads V1 and V2. These leads are reciprocal to the POSTERIOR wall, otherwise known as the upper part of the inferior wall. If an inferior wall M.I. is large enough, it can produce ST elevation in the posterior leads (not performed in this case), and ST depression in the anterior leads, especially V1, V2, and V3.

The rhythm is a marked sinus bradycardia, at just under 40 beats per minute. Sinus bradycardia is very common in inferior wall M.I., because the inferior wall and the sinus node are usually both supplied by the right coronary artery. AV blocks can also occur because the AV node is also supplied by the RCA in most people.

It is important to remember that bradycardia does not always need to be treated. In patients with acute M.I., a well-tolerated bradycardia may actually be beneficial to the injured heart, reducing supply/demand ischemia. A well-tolerated bradycardia is a rate that does not produce low blood pressure and poor peripheral perfusion. Some people tolerate rates in the 40’s quite well. If the patient shows signs of poor perfusion: low BP, decreased mentation, pallor, shortness of breath, the rate should be cautiously increased with medication or electronic pacing.

Inferior Wall ST-elevation M.I.

Submitted by Dawn on Sun, 02/24/2013 - 12:24

This is an excellent example of acute inferior wall ST elevation M.I. (STEMI) in a 78 year old woman who had been experiencing intermittent chest pain for two days. This 12-lead ECG has been formatted to simultaneously produce three rhythm strips below the 12-Lead. The rhythm strips are run simultaneously with the 12-Lead, and show 3 different leads. This feature can been invaluable when trying to decipher complex rhythms.

In this case, the patient is in normal sinus rhythm, and has classic ST segment elevation in the inferior wall leads: II, III, and aVF. There is some reciprocal ST depression in Leads I and aVL, and also in V1 and V2, suggesting injury extending up the posterior wall. ST depression is noticeable in V6 as well. This patient's RCA lesion was opened and stented, and she did well immediately post cath. We have no records past that.