• The free wall of the right ventricle (RV) is supplied by the marginal (RM) branches of the right coronary artery (RCA).
• Electrical activity of the RV free wall is detected by the right-sided leads (V1R-V6R) placed over the right side of the patient's anterior chest, mirroring the precordial leads placed over left anterior chest.
• Since right-sided leads are not part of the standard 12-lead ECG, right ventricular STEMI is often silent (easily missed).
• Patterns of right ventricular STEMI, corresponding ECG leads exhibiting ST elevation, and culprit lesion(s) are listed below:
Isolated right ventricular --- V1 or V3R-4R --- RCA-RM
Inferior-right ventricular --- II, III, aVF + V1 + V3R-4R --- RCA or RCA/LCx-PDA
• Because the right coronary artery (RCA) also supplies blood to the SA and AV nodes, right ventricular MI is often associated with conduction block such as sinus node dysfunction and AV block.
• Isolated right ventricular (RV) free wall MI is very rare. Most MIs involving the RV also involve the inferior wall of the left ventricle (LV). This is because in order to cause an infarct of the entire RV free wall, the occlusion must occur at the proximal right coronary artery (RCA) which will inadvertently impair distal flow to the posterior descending artery (PDA) supplying the LV inferior wall.
• RV free wall MI arises when there is occlusion(s) of either the --
Marginal (RM) branch(es) of the RCA supplying a large part of the RV free wall,
Proximal non-dominant RCA with PDA branching from an intact left circumflex (LCx), or
Proximal dominant RCA with adequate collateral flow from the left-sided circulation to the LV inferior wall
• ECG findings associated with right ventricular free wall MI include:
ST elevation in right-sided leads (V3R-6R, most sensitive/specific lead is V4R)
ST elevation in right anterior (V1-2) and right inferior (III) leads
• On echocardiography, there is hypo/akinesis of the RV free wall (shaded in grey below) seen in apical 4 chamber, parasternal long and short axis views.
• Inferior-RV MI is caused by occlusion(s) of the --
Proximal dominant right coronary artery (RCA) and its branches including the posterior ascending artery (PDA),
Proximal non-dominant RCA and PDA of the dominant left circumflex artery (LCx), or
Proximal non-dominant RCA and distal wrap-around left anterior descending artery (LAD)
• ECG findings associated with inferior-RV MI include:
ST elevation in inferior (II, III, aVF) and right-sided (V1R-6R) leads
ST elevation in III greater than ST elevation in lead II
Reciprocal ST depression in lateral leads (I, aVL)
• On echocardiography, there are hypo/akineses of the inferior and RV free walls (shaded in grey below) seen in apical 4- and 2- chamber, and parasternal long and short axis views.
