Precordial leads

May manifest as tall R waves in the right precordial leads and ST-segment depression in leads Vj - V4... 

Obtain right precordial leads in any patient with an inferior wall myocardial infarction... 

The electrocardiogram can be obtaining using standard limb leads and/or precordial leads. A lead should be selected that is stable over time and that has a sharp demarcation at the end of the T wave to facilitate the measurement of the QT interval duration. One can also position a monophasic action potential electrode catheter through the femoral or carotid artery to obtain endocardial monophasic action potentials (see below Modification of the Method). 

Fujiki A, Usui M, Nagasawa H, Mizumaki K, Hayashi H, Inoue H. ST segment elevation in the right precordial leads induced with class IC antiarrhythmic drugs insight into the mechanism of Brugada syndrome. J Cardiovasc Electrophysiol 1999 10(2) 214-18. 

The VR lead is usually not taken into account by the cardiologist when interpreting an ECG. Nonetheless, ST-segment elevation in VR is very important in the presence of an STE-ACS in the precordial leads because it suggests that LAD occlusion is proximal to SI (Figures 4.18 and 4.19). 

Figures 3.18 and 3.19 show the evolution of two Mis from the acute phase with a huge ST-segment elevation until the appearance of Q wave of necrosis and negative T wave of subepicardial ischaemia. In Figure 3.20, a patient with chronic MI of inferior wall presents in the same ECG a different grade of ECG pattern of subepicardial ischaemia (negative and deep T wave in inferior leads, tall and positive T wave in right precordial leads as a mirror pattern and flat T wave in V6).

Figure 4.3 Observe how an amplified ECG (4x) allows the proper assessment of ST-segment deviation. (A) Post-myocardial-infarction patient with slight ST-segment elevation in right precordial leads. When amplified ECG...

Figure 4.16 Acute myocardial infarction in a patient with rapid atrial fibrillation. The ECG shows ST-segment elevation in V2-V5, I and VL. Leads II, III, and VF present an evident ST-segment depression as a mirror pattern of ST-segment elevation in precordial leads. This is a pattern of acute coronary syndrome with ST-segment elevation of the anterior wall according to the classical classification.

ST elevation in precordial leads and VL ST elevation in inferior wall and/or lateral /eac/st... 

Also, the ST-segment elevation is seen in the precordial and inferior leads in the presence of an STE-ACS due to the very proximal occlusion of the RCA before the RV marginal branches. In this case usually the ST-segment elevation in VI > V3-V4, while in an STE-ACS due to the distal occlusion of the LAD, the contrary occurs (i.e. the ST-segment elevation is VI < V3). Table 4.2 shows the ECG criteria that allow differentiating the culprit artery (proximal RCA or distal LAD) in the case of ST-segment elevation in precordial leads and inferior leads. 

Table 4.2 The ST segment elevation in precordial leads (especially V1- V3-V4) and inferior leads (II, III and VF).

Inferior leads Usually ST t greater than in precordial leads, if not (Figure 10.4) there is ST fin V1 that is not seen in LAD distal occlusion ST t usually smaller than in precordial leads... 

In exceptional cases of proximal occlusion of very dominant RCA, the ST-segment elevation may be seen in all precordial leads, in V1 to V3-V4 due to proximal occlusion and in V5-V6 due to very dominant RCA (local injury vector) (see Figure 8.39). 

Incomplete occlusion of LAD involving diagonal but not septal branches or selective occlusion of Dl Often ST-segment elevation in I, VL and V5-V6 and sometimes even in more precordial leads, and ST-segment depression in II, III and VF (III > II). 

Figure 4.32 Usefulness of the ST/T changes in the extreme right precordial leads (V4R) to differentiate among the proximal RCA (A), distal RCA (B) and LCX involvement (C).

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