Subendocardial ischaemia

The same pattern (STf in VR) in case of an NSTE-ACS with ST-segment depression in many leads suggests the incomplete occlusion of the left main trunk (LMT) (Yamaji et al, 2001) or its equivalent (very proximal LAD occlusion + LCX) in patients with previous subendocardial ischaemia (Figures 4.59-4.61). 

ECG pattern for subepicardialischaemia) or symmetric and usually taller-than-normal T wave with QTc prolongation (ECG pattern of subendocardial ischaemia) located in different leads according to the corresponding affected zone - anteroseptal or inferolateral (see Experimental point of view -below - and Figure 3.5). 

The ECG pattern of subepicardial ischaemia, is more consequence of previous ischaemia than due to the presence of active ischaemia. On the contrary, the ECG pattern of predominant subendocardial ischaemia (symmetric and usually taller-than-normal positive T wave accompanied by rectified ST segment and prolongation of QTc interval) represents the first ECG change induced by active ischaemia (Figure 3.7). 

In the VCG the T wave of subepicardial ischaemia, which is the only one that is usually recorded because the T wave of subendocardial ischaemia is very transient, presents a T loop of homogeneous inscription and frequently small and more or less rounded, although it may be very narrow in some planes (Figure 3.17). 

When acute coronary occlusion is carried out in experimental animals with closed thorax, it gives rise, during the initial phase of ischaemia, to a delay in repolarisation (TAP) in the subendocardium, which is the area that first suffers ischaemia (Lengyel et al, 1957). This subendocardial ischaemia is evidenced by a tall and peaked T wave immediately followed by ST-segment elevation (injury pattern) if the occlusion persists and the ischaemia becomes severe and transmural (see ECG pattern of injury p. 55). This pattern maybe self-limited if the occlusion is temporary, as in coronary spasm (Prinzmetal... 

Figure 3.5 Explanation of how the sum of the TAP from the subepicardium and the subendocardium explain the ECG, both in the normal situation (A), as in the case of subendocardial ischaemia (B) (tall and peaked T wave) and...

In some cases of coronary artery spasm of just a few seconds duration, the reversible subendocardial ischaemia pattern may be the unique electrocardiographic change recorded. Sometimes, while passing from one pattern to another (from a posi-... 

Electrocardiographic pattern of subendocardial ischaemia diagnosis and differential diagnosis... 

The ECG pattern of subendocardial ischaemia -a T wave more symmetric and often taller preceded by rectified ST segment and accompanied by... 

QTc prolongation (T wave of subendocardial ischaemia) - is observed in the acute phase of IHD (Table 2.1 A) but may also be seen in other situations (Table 3.1). 

The T wave of subendocardial ischaemia is a temporary pattern that may be recorded during a brief time in the hyperacute phase of STE-ACS (Figure 8.7) and during a coronary spasm (Figure 8.46)... 

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...

Figure 4.59 (A) The ECG of a patient with ACS and the ECG typical of tight but incomplete occlusion of the left main coronary artery (see coronary angiography) (B) in the presence at basal state of important and circumferential subendocardial ischaemia. There is ST-segment depression in more than eight leads and clear ST-segment elevation in VR. Note that the maximum depression occurs in V3-V4 without final positive T wave in V4-V5.

Now we will discuss the evolving electrocardiographic patterns that can appear throughout the occlusion of an epicardial coronary artery and its prognostic implications (Figures 3.18,3.19 and 8.5). (a) Subendocardial ischaemia (symmetric and peaked T wave and usually taller)... 

ECG pattern of subendocardial ischaemia and the pattern of subepicardial ischaemia. Slight ST-segment elevation may be noted in V1 lead. (B) Few hours later appeared typical pattern of subepicardial injury (ST-segment elevation) with QS of necrosis in V2-V4. 

This ACS with regional involvement is usually secondary to an incomplete coronary artery occlusion in patients frequently presenting with prior predominantly regional subendocardial ischaemia and single- or multivessel disease, but one culprit artery. Any coronary artery may be the culprit one and the occlusion often is not proximal (Table 8.2). 

Figure 8.46 Above Crisis of coronary spasm (Prinzmetal angina) recorded by Holter ECG. (A) Control. (B) Initial pattern of a very tall T wave (subendocardial ischaemia). (C) Huge pattern of ST-segment elevation. (D-F) Resolution towards normal values. Total duration of the crisis was 2 minutes. Below Sequence of a crisis of Prinzmetal angina with the appearance of ventricular tachycardia runs at the moment of maximum ST-segment elevation.

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