Inferolateral infarction

Fig. 14.2. Complete right posterior cerebral artery (PCA) territorial infarct.Notice the anterolateral mesencephalic and the inferolateral thalamic infarcts. Old left striatocapsular infarct...

When adenosine (70 micrograms/kg/minute) was given by intravenous infusion to 45 patients with acute myocardial infarction preceding balloon angioplasty, one patient developed persisting hypotension in conjunction with a large inferolateral myocardial infarction (18). Transient hypotension in three other patients resolved with a reduction in dosage. There were no cases of atrioventricular block. 

A previously healthy 19-year-old man took tablets containing a total of 24 mg of Ephedra alkaloids and 100 mg of caffeine, and 15 minutes later developed severe chest pain radiating down the left arm. An electrocardiogram showed an inferolateral myocardial infarct, confirmed by creatine kinase and troponin I measurements. He made a full recovery, and coronary angiography showed only minimal atherosclerotic disease of the left anterior descending artery. 

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). 

We should remember that in some chronic coronary patients, those who present a transmural infarction classically named inferoposterior but with the new classification we define as inferolateral MI (Figure 5.9B(3)), a tall, frequently peaked, and in this case persistent, T wave may be recorded in V1-V3 as a consequence of the changes that the transmural infarction produced in repolarization (mirror pattern of inferobasal and lateral subepicardial ischaemia) (Figure 3.10). 

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 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,...

In Figures 5.4 and 5.5 the changes that, as a consequence of the presence of the vector of infarction, are generated in the ventricular depolarisation loops in the presence of two prototype infarctions (anteroseptal and inferolateral areas, respectively) are represented. Said changes explain the presence of Q waves in the different leads by means of the loop-hemifield correlation. Some of the ECG morphologies and the QRS loops correlations in the seven types of infarctions, according to the classification... 

Figure 5.5 (A) See the comparison between normal activation and activation in case of inferolateral infarction. The vector of infarction is directed upwards and a...

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... 

Electrocardiographic pattern of the inferolateral infarction (Figure 5.9B(3)) diagnostic criteria supporting the RCA or the LCX being the culprit arteries... 

The inferolateral infarction due to an RCA occlusion generates an infarction vector that points upwards and a little rightwards, and anteriorly. 

In inferolateral infarction due to RCA occlusion, there are more signs of inferior than of lateral infarction, and, in any case, the latter may be manifested by an RS in VI and in some cases by abnormal q wave in the left precordial leads, but not by q wave in leads I and VL (Figure 5.33). In turn, in inferolateral infarction due to LCX occlusion, the lateral wall is more involved than the inferior wall, and this explains why a Q wave may be recorded in I, VL, V5 and V6, though usually a QR, instead of a QS, pattern is seen. Also, according to the loop-hemifield correlation, the Q wave in II, III and VF may be more important... 

In some cases of inferolateral involvement, especially due to RCA occlusion, there is a clear sign of inferior infarction but no evidence of lateral infarction (no q in lateral leads and/or R in VI). In our experience the contrary inferolateral involvement with only ECG evidence of lateral infarction occurs less frequently. 

Figure 5.37 ECG of a patient with two Mis, one apical and the other inferolateral. The presence of QR in V1, RS in V2 and qR with wide q in III is the abnormal QRS change. The QR pattern of V1 is explained by double infarction (apical + inferolateral). However, there are not many leads with Q wave in spite of clinical and isotopic evidence of double...

Figure 5.46 (A) Patient with complete right bundle branch block in acute phase of inferolateral infarction.

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...

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. 

Anteroseptal versus inferolateral MI prognostic implications. It is known that the MI involving LAD presents for similar area of necrosis, increased myonecrosis, reduced early and late left-ventricular function and high mortality compared with infarction in other vascular territories. However, the mechanisms underlying a worse prognosis are not completely characterised. Recently, it has been demonstrated (Kandzari et al, 2006) that prognosis after primary PCI in patient with ACS, the majority with ST-segment elevation, is different in patients with LAD occlusion than in RCA or LCX. Acute myocardial infarction due to LAD is associ-... 

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. 

This infarction never occurs in isolation (Zimmerman, 1968). In acute phase oflarge inferolateral infarctions or, less frequently, of anteroseptal infarctions, the presence of PR-segment deviations, atrial arrhythmias and/or abnormal P waves (notched, irregular shape) suggests that atrial involvement has occurred. This probably occurs rarely, although this has to be studied with new image techniques (CE-CMR). 

From the prognostic point of view, these usually correspond to large anteroseptal or inferolateral infarctions. In case of acute inferior MI the presence of PR-segment depression >1.2 mm in inferior leads has been demonstrated to be a marker of higher risk of in-hospital mortality and cardiac rupture (Jim et al., 2006) (Figure 10.6). Often these cases present supraventricular arrhythmias, especially atrial fibrillation. 

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). 

Bayes de Luna A, Cino J, Kotzeva A et al. New ECG criteria of inferolateral myocardial infarction assessed by contrast enhanced-cardiovascular magnetic resonance based on the morphology of QRS in VI. Eur Heart J Supl 2006b 27 871. Abstract. 

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