Injury vector

The injury vector has approximately the same direction as that of the vector of ischaemia and infarction but opposite sense (see p. 35, 60 and 131 and Figures 3.6, 4.8 and 5.3). Therefore, most probably, in case of injury of the lateral wall, an ST-segment depression will be especially recorded in V1-V2, and in case of injury of the inferobasal wall, the ST-segment depression will be recorded especially in V2-V3. However, further perfusion studies, with imaging techniques in the acute phase have to be done to validate this hypothesis. 

It should be noted that the infarction vector also moves away from the infarction area (p. 133), while the injury vector is directed towards the injured area (p. 58). 

As can be observed in the VCG, the final part of QRS loop (2 in Figure 4.14) is displaced from the beginning (1 in Figure 4.14), the free space being the expression of the injury vector (see distance 1-2 in Figure 4.14). 

Theory of the injury vector (Figures 4.6-4.8) The electrocardiographic pattern of suben-... 

Figure 4.8 Subendocardial (A) and subepicardial (B) injury vectors in case of experimental (1) or clinical (transmural) injury (2).

Both the clinical ST-segment depression pattern and the experimental subendocardial injury pattern have a common explanation the sum of subendocardium TAP, which is of worse quality than in the subepicardium (Figure 4.5), or the generation of an injury vector (Figure 4.8). In NSTE-ACS the presence of new ST-segment depression is related with the presence of evident active ischaemia predominantly in the subendocardium. On the other hand, the presence of flat or negative T wave is related with previous ischaemia (often is a reperfusion pattern) without subendocardial predominance (Table 2.1 and Figure 3.9). 

Figure 4.9 (A) In case of diffuse subendocardial circumferential injury due to incomplete occlusion of left main trunk (LMT) in a heart with previous important subendocardial ischaemia, the injury vector that points circumferential subendocardial area is directed from the apex towards the base, from forward to backwards and from left to right. This explains the typical morphology of...

ST-segment depression in all the leads except VR and V1, with maximal ST-segment depression in V3-V5. As the injury vector faces more VR than V1 the ST-segment elevation in VR > V1. (B) Typical ECG of LMT critical subocclusion. The ST-segment depression is higher than 6 mm in V3-V5 and there is not evident final positive T wave in V4-V5. 

In theory the presence of subendocardial or transmural injury in completely opposite areas of the heart may decrease or even conceal the two injury vectors (Madias, 2006). However, in practice, this does not occur usually, because the ischaemia is usually due to occlusion of only one vessel and this does not generate equal and opposed injured areas (Rautaharju, 2006). Furthermore, with the same amount of injury in two opposite areas, it is more visible in the surface ECG of the injury area that is more close to subepicardium. In the chronic phase it is more often seen that a new vector of infarction in opposed area may cancel the Q-wave pattern of a previous infarction (see Figure 5.38). 

Figure 4.10 In an acute coronary syndrome with ST-segment elevation in V1-V2 to V4-V6 as the most striking pattern, the occluded artery is the left anterior descending coronary artery (LAD). The correlation of the ST-segment elevation in V1-V2 to V4-V5 with the ST morphology in II, III and VF allows us to know if it is an occlusion proximal or distal to D1 (see Figure 4.43). If it is proximal, the involved muscular mass in the anterior wall is large and the injury vector is directed not only forward but also upward, even though there can be a certain...

Figure 4.11 In an acute coronary syndrome with ST-segment elevation in II, III and VF as the most striking abnormality, the study of the ST-segment elevation and depression in different leads will allow us to assure if the occluded artery is RCA or LCX and even the site of the occlusion and its anatomical characteristics (dominance, etc ). This figure shows that the presence of ST-segment depression in lead I means that this lead is facing the injury vector tail that is directed to the right and, therefore, the...

Figure 4.14 ECG and VCG in two cases (A, B) of anterior subepicardial injury. See the injury vector (arrows between 1 and 2).

Figure 4.15 Subacute phase of inferolateral infarction. The ECG shows Q in II, III, VF, RS in V1 and tall R wave in V2, with ST-segment depression in V1-V3 and ST-segment elevation in II, III and VF. The inferolateral subepicardial injury vector is directed towards the injured zone (downwards and backwards) and therefore produces ST-segment depression in V1-V3, as well as ST-segment...

In this case, the injury vector is directed anteriorly, upwards and somewhat to the left (Figure 4.20D). The projection of the injury vector in different positive and negative hemifields of different leads of FP and HP explains the ST-segment elevation from V2-V3 to V5-V6. However it does not usually explain the ST-segment elevation in V1 because the projection of this vector in the HP falls often a little to the left in the limit of negative hemifield of VI or close to it. Also, these correlations explain the ST-segment elevation in lead I, especially in VL, and the ST-segment depression in the inferior leads (III + VF > 2.5 mm)... 

Figures 4.20 and 4.21). Usually, more ST-segment depression is seen in III than in II, since lead III is opposed to VL, and therefore the injury vector falls more in the negative hemifield of III and more directly this lead faces the injury vector tail (Figure 4.21). 

In this case, the injury vector is also directed anteriorly and often rather to the left and usu-... 

Figure 4.21 (A) The ECG in STE-ACS due to LAD occlusion, proximal to D1, but distal to S1. Observe the ST-segment elevation from V2 to V5, with ST-segment depression in II, III, and VF more evident usually in III than II due to the direction of injury vector. There is neither ST-segment...

Figure 4.22 STE-ACS due to occlusion of long LAD, distal to D1 and S1. (A) Site of occlusion (B) myocardial area at risk (C) involved segments in bull s-eye projection (D) injury vector directed forward but somewhat downwards...

The injury vector is directed anteriorly and to the right because the injury vector faces the anteroseptal area and often downwards (occlusion distal to Dl), especially if the LAD is long and wraps the apex, affecting part of the inferior wall. Then, if the anterior wall is not greatly affected because the occlusion occurs below a big Dl, the involvement of the inferior wall can turn out to be more important than the involvement of the anterior wall. The projection of this injury vector in the positive and negative hemi-fields of different leads of FP and HP explains the ST-segment elevation from VI to V4 and... 

The injury vector is directed upwards, leftwards and forwards (Figure 4.26D). According... 

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). 

The injury vector is directed anteriorly, upwards and to the right (Figure 4.28D) and, there-... 

Figure 4.25 Above (A) STE-ACS due to LAD occlusion proximal to S1 but distal to D1. (A) The site of occlusion. (B) Myocardial area at risk. (C) Bull s-eye polar map with involved segments. (D) Injury vector directed to the right and forwards due to occlusion proximal to S1. In case of a long LAD involving also inferior wall, the vector can be directed somewhat downwards due to relatively small myocardial area of anterior wall involved in case of occlusion distal to D1. The occlusion distal to D1 explains the ST-segment elevation from V1 to V3-V4 and...

The vector of injury in cases of infarction due to non-proximal occlusion of the RCA is directed downwards posteriorly and to the right. Due to the RV extension in case ofveryproximal RCA occlusion, the injury vector is directed more to the right than posteriorly (compare Figures 4.30D... 

B) Myocardial area at risk. (C) Polar map in bull s-eye projection with the most involved segments marked in gray. (D) Injury vector projected on frontal, horizontal and... 

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