Chest Pain and Shock: Is There a Right Ventricular OMI on This ECG? and Should He Undergo Trancutaneous Pacing?
Highlights
- any STE in V1 in the setting of inferior OMI is very specific and about 70% sensitive for right ventricular OMI. This is because V1 sits directly over the RV.
HOWEVER, this only applies when there is NO ST depression in V2. STD in V2 "pulls down" the ST segment in V1 thus negating any sign of RV MI.
In fact, if there is significant STD in V2, but NONE in V1, that is a sign of probable RV MI, as you would expect associated STD in V1 with such a posterior OMI. (View Highlight)
- Atropine usually works in junctional rhythm with a narrow complex (View Highlight)
- Transcutaneous pacing should not result in subsequent pacing insensitivity unless the escape is infra-Hissian (below the bundle of His). Such an escape would have a wider complex. (View Highlight)
- approximately 80-90% of patients have a "right-dominant" circulation. In these patients, after supplying the RV (right ventricle) — the RCA continues as the PDA (Posterior Descending Artery) along the undersurface of the heart to supply the posterior and inferior walls of the LV (left ventricle) — and sometimes the lateral wall with postero-lateral branches off the PDA. (View Highlight)
- about 15% of patients have a left-dominant circulation, in which the RCA is less prominent. To compensate, the LCx (Left Circumflex) artery is a relatively larger vessel, and it (rather than the RCA) provides most (or all) of the blood supply to the PDA. As a result, not only the lateral — but also the inferior and posterior walls of the LV are predominantly supplied by LCx artery in patients with a left-dominant circulation. (View Highlight)
- Acute occlusion (OMI) of either the RCA or the LCx may result in acute infero-postero-lateral MI (although statistically — the RCA will much more commonly be the "culprit" artery) (View Highlight)
- Among the ECG features that further support the likelihood of the RCA as the "culprit" artery are: i) ST elevation in lead III>II; — ii**)** Marked reciprocal ST depression in lead aVL; iii) Relatively less (or no) lateral ST elevation, with the amount of ST elevation in lead III>V6; and, iv) Evidence of acute RV involvement (View Highlight)
- The LCx does not supply the right ventricle. Therefore, if there is ECG evidence suggesting acute RV involvement in association with inferior STEMI — this is virtually diagnostic of the proximal RCA being the "culprit" artery (since the RV is supplied by this initial part of the RCA) (View Highlight)