Electrocardiographic changes secondary to myocardial ischaemia

The importance of ECG to detect myocardial ischaemia correlation with imaging techniques 

Myocardial ischaemia is the name given to the decrease in the perfusion of a certain area of the myocardium. Therefore whenever the oxygen supply is not sufficient for demands, a state of myocardial ischaemia occurs. This may be caused by (1) acute diminution of a coronary blood flow (ACSs and MI), which is usually secondary to the complete or partial occlusion of a coronary artery due to atherothrombosis, and (2) when there is an increase of a myocardial oxygen demands. The latter happens with exercise in cases in which impaired myocardial perfusion already exists, especially in the subendocardium when the coronary arteries have a diminished ability to increase a coronary blood flow (exercise angina). We have to remind that the subendocardium is more vulnerable to myocardial ischaemia because its vasodilatory capacity is less, and this vulnerability increases during exercise (tachycardia) (see p. 57). 

Generally, the clinical presentation of myocardial ischaemia is the characteristic pain known as angina pectoris or some equivalents (e.g. dyspnoea), although sometimes ischaemia may be silent (see Silent ischaemia , p. 302). If the anginal pain is new or if it has increased with respect to previous discomfort (crescendo angina), this constitutes the clinical condition called acute coronary syndrome (ACS), which may evolve into myocardial infarction (MI) (see Section Acute coronary syndrome , p. 209). If the angina pain appears with exercise 

The concept of the electrocardiographic patterns of ischaemia, injury and necrosis (Sodi Pallares, 1956,1968 Cabrera, 1966) 

We will now briefly define the classical ECG patterns of ischaemia, injury and necrosis, and later on (sections Electrophysiological mechanism of the ECG pattern of ischaemia to ECG pattern of necrosis ) we will explain these in detail. 

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CHAPTER 2 Electrocardiographic changes secondary to myocardial ischaemia 21... 

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