This ECG was recorded from a 75-year-old man with substernal chest pain and diaphoresis. It shows a pretty classic picture of acute inferior wall M.I. The second ECG is a repeat tracing with the V4 wire moved to the V4 Right position, and it is positive for right ventricular M.I. The patient was found to have a 100% occlusion of the right coronary artery, which was opened and stented in the cath lab.
There are several other examples of IWMI with RVMI in our archives, so we will confine this commentary to the ECG signs that make these tracings so typical of right coronary artery occlusion. Once you are familiar with the typical pattern of IWMI / RVMI, it is easy to see, even when the ST elevation is subtle (as this one certainly is NOT).
Signs of IWMI in these ECGs are:
· ST elevation in inferior leads II, III and aVF.
· Reciprocal ST depression in leads I and aVL.
Signs of RVMI in these ECGs are:
· ST elevation in V4 right.
· ST elevation in V1 without ST elevation in V2.
· ST elevation in lead III is greater than ST elevation in lead II.
Other common findings in right coronary occlusion that are seen in these ECGs:
· ST depression in V2. If not for the RVMI causing elevation in V1, there would be ST depression in V1 also. This is a reciprocal ST depression, reflecting STE in the posterior wall. The posterior wall is called the lateral wall by some because it is oriented behind the anterior wall, but toward the patient’s left side. This area across from V1, V2, and sometimes V3 can have ST elevation if an inferior wall M.I. is large enough to extend up toward the base of the heart. Electrodes placed on the left side of the back might show the STE.
· Bradycardia and heart block. Sinus and AV node blocks often occur in IWMI because the two nodes usually have the same blood supply as the inferior wall and right ventricle. AV blocks are usually of the “Type I” variety. There may be varying amounts of first-degree AVB, second-degree AVB, Type I (Wenckebach), and even third-degree, or complete heart block. In the first ECG, at 3:17, we see some 2:1 AVB. There are also some periods where there is AV dissociation with junctional escape, or possibly very long PR intervals (beats 1,5,6). In the second ECG, at 3:27, we see a slight increase in the sinus rate with Wenckebach periods (beats 5-8).
· Bradycardia, even if caused by AV block, might actually be helpful to the M.I. patient, as a rapid rate could use up the heart’s resources and hasten heart failure. The rate should be evaluated in light of the patient’s hemodynamic condition: blood pressure, skin color and temperature, and mental status.
Being able to quickly and confidently recognize the patterns produced by RCA occlusion will help when you are confronted with a symptomatic patient whose ECG has minimal ST elevation.
Our thanks to Palm Beach Gardens, FL Fire Rescue for donating these ECGs.
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