Repolarisation changes

Figure 3.27 The mixed repolarisation changes (C) are explained by the combination of the primary changes due to ischaemia (A) and the changes secondary to the depolarisation abnormalities (e.g. LVH) (B).

The morphology of ST-segment depression is more difficult to assess in the presence of a wide QRS complex or LVE. In this situation mixed repolarisation changes can be observed (alterations secondary to LVH or LBBB and primary alterations due to ischaemia) (see ECG pattern of injury in patients with ventricular hypotrophy and/or wide QRS ) (p. 120). 

We will refer to the diagnosis in the chronic phase. The hemiblocks do not alter the repolarisation changes that can be observed in the acute phase of MI. 

The markers of poor prognosis are the following (1) Repolarisation changes (ST/T)... 

The Q-wave infarction is diagnosed by the development of a new Q wave plus enzyme-level increase (CPK or troponin-level rise). Because of the setting in which the Q-wave infarction occurs, repolarisation changes that precede it are sometimes difficult to assess, but sometimes a clear ACS with ST-segment elevation may be diagnosed. 

In probably more than 50% of cases, an MI with normal intraventricular conduction and narrow QRS does not show a Q wave of necrosis or equivalent (R in V1-V2). However, it may show anomalies in the mid-late part of QRS (as low r in lateral leads, rsr , slurrings, etc. (fractionedQRS)). Also repolarisation changes may be recorded especially in the acute phase. The incidence of MI without Q wave is variable depending on whether it is detected. In the emergency department it is higher and in the CCU lower. 

These repolarisation changes in the extreme right precordial leads are seen only in the hyperacute phase of infarction. Therefore, their absence does not rule out the diagnosis of an RV infarction in the subacute phase. According to our experience,... 

If the delay is subepicardial or even transmural (see The concept of ECG patterns of ischaemia, injury and necrosis ) (p. 20). this delay of repolarisation without change of shape of TAP generates a flattened or negative T wave. 

Figure 3.9 In case that in basal state a certain degree of ischaemia with subendocardial predominance exists too mild to produce clear ECG changes, an increase of active ischaemia still with subendocardial predominance will produce an ST-segment depression (subendocardial injury pattern) (A). If as a consequence of ischaemia there is a delay in repolarisation predominating in subepicardium or being transmural, a flattened or negative T wave appears in leads with, but also without, predominant R wave (B-1) (subepicardial ischaemia pattern). The latter pattern is...

The ECG pattern of subepicardial ischaemia -flattened or negative T wave - is observed in IHD (Table 2.1), but it may also appear in other situations (see Table 3.2). We have to remember that the ECG pattern of subepicardial ischaemia (negative T wave) although may probably be due to real active ischaemia (ACS), more often appear in the dynamic changes of some ACS as a reperfusion pattern or is explained by the changes that MI has induced in ventricular repolarisation (chronic Q-wave MI) (p. 37 and Table 8.1). 

Figure 4.1 Holter recording of a very young patient with early repolarisation pattern recorded at night (A) that disappeared at daytime (B). During tachycardia the repolarisation presents changes typical of sympathetic overdrive (C).

Figure 4.51 Above Examples of four types of repolarisation alterations that can be seen in sportsmen without heart disease (Plas, 1976). Below Drawings of more typical changes in V2.

With respect to chronic repolarisation abnormalities, the negative T wave is more symmetric than that in the isolated complete LBBB (Figures 3.40 and 1.58). In clinical practice positive T wave in V5 and V6 is usually seen when the LBBB is not too advanced, and septal repolarisation does not predominate completely over left-ventricular repolarisation. In some cases it may be the expression of changes of repolarisation polarity induced by ischaemia. 

As we have discussed previously ( cardiac memory in the intermittent LBBB and WPW syndrome), patients with intermittent right-ventricular stimulation, when the stimulus is conducted via the normal path (Figure 3.35), can show a cardiac memory phenomenon (lack of adequacy of the repolarisation to the depolarisation changes), which explains the anomalous repolarisation (negative T wave) that is sometimes observed, in sinus rhythm in the absence of IHD. It has been demonstrated that in this situation, the T wave is negative in precordial lead but is positive in I and VL (see Figure 3.35, p. 52). 

A) tall and/or wide T waves in inferior leads (B) abnormal ST-segment elevation, with no changes of the final part of QRS (C) important ST-segment elevation and distortion of the final part of QRS. (2) The three types of repolarisation... 

Figure 8.21 The ECG recorded during ACS (B) represents subtle changes of the repolarisation (more positive T wave in V2-V4, somewhat more evident ST-segment depression in inferior leads and V6) as compared to previous ECGs (A). These features suggest inferolateral involvement, as it was...

The electrocardiographic changes, when present, are of STE-ACS type and, frequently, with evolving Q-wave infarction. Furthermore, there is a risk for a false-positive diagnosis, since in the young population consuming cocaine, the pattern of early repolarisation is also frequently seen. 

ECG recordings with QS morphology in V1-V2 may be seen due to septal fibrosis or in elderly patients. This pattern most probably corresponds to an old infarction when this is recorded in patients with chronic IHD and is accompanied by changes of repolarisation suggestive of ischaemia. The presence of Q waves in certain leads does not rule out the presence of viability in the correlated cardiac segments (Schinkel et al., 2002). 

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