Inferolateral zone infarction

Both acute coronary syndromes (ACSs) and infarcts in chronic phase affect, as a result of the occlusion of the corresponding coronary artery, one part of the two zones into which the heart can be divided (Figure 1.14A) (1) the inferolateral zone, which encompasses all the inferior wall, a portion of the inferior part of the septum and most of the lateral wall (occlusion of the RCA or the LCX) (2) the anteroseptal zone, which comprises the anterior wall, the anterior part of the septum and often a great part of inferior septum and part of the mid-lower anterior portion of lateral wall (occlusion of the LAD). In general, the LAD, if it is large, as is seen in over 80% of cases, tends to perfuse not only the apex but also part of the inferior wall (Figures 1.1 and 1.14). 

Figure 4.17 Acute myocardial infarction with ST-segment elevation in II, III and VF and ST-segment depression in V1-V3. This pattern corresponds classically to an infarction involving inferior and posterior walls. Nowadays, this is the pattern of STE-ACS of inferolateral zone evolving to inferolateral infarction due to distal occlusion of a dominant RCA (ST-segment depression in I and V1-V3,...

Figure 5.9). Seven infarcted areas due to first MI have been found to have a good correlation with seven electrocardiographic patterns (Cino et al., 2006). Four of these are located in the anterosep-tal zone, while the remaining three in the inferolateral zone, the former being secondary to occlusions in different segments of the LAD and its branches and the latter due to RCA or LCX occlusion... 

Figure 8.13 (1) The three types of repolarisation abnormalities that may be seen in an acute phase of myocardial infarction involving the inferolateral zone ...

We will just remind (see p. 137) that seven areas of MI detected by CE-CMR have good correspondence with seven ECG patterns (four in anteroseptal zone - septal, apical-anterior, extensive anterior and mid-anterior - and three in the inferolateral zone - inferior, lateral and infero-lateral) (Figure 5.9 Cino et al., 2006). We have also demonstrated that in clinical practice the presence of these seven ECG patterns correlates well with the corresponding infarction areas detected by CE-CMR, and therefore these have real value in clinical practice (Bayes de Luna et al., 2006a-c) (Table 5.3). Therefore, in chronic infarction the correlation between ECG changes (Q waves of necrosis) and involved area (CE-CMR) is clearly good (88% global concordance). However, the in-farcted area of apical infarction (A-2 type), mid-anterior infarction (A-3 type) and lateral infarction (B-l type) presents the lower concordance. 

The presence of many electrocardiographic criteria showing inferior and lateral involvement represents generally a large infarction that encompasses the cases of worst prognosis of MI of inferolateral zone, especially in case of MI due to very dominant RCA or LCX. The ejection fraction is usually diminished. Therefore, in the acute phase, quick decision should be taken (urgent PCI) to avoid haemodynamic complications. 

Some Q-wave infarctions may exhibit normal or near-normal ECG recordings in the chronic phase. They are usually but not always small septal, mid-anterior, inferior or lateral infarctions that, generally, in the acute phase exhibit ST-segment elevation in the corresponding leads, accompanied by a Q wave. Relatively often, especially in the inferolateral zone or in septal or mid-anterior infarction, the Q wave disappears over time (Figure 8.12 Bayes de Luna et al, 2006a-c). 

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...

Figure 5.52 The ECG of a patient with complete LBBB and associated infarction. There are ECG criteria suggestive of extensive anterior myocardial infarction (qR in I, QR in VL and low voltage of S in V3). The CMR images (A-D) demonstrated the presence of an extensive infarction of anteroseptal zone (type A-3) (proximal LAD occlusion). The inferolateral wall is free of necrosis (see (D)), because the...

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