Anatomy - Risk assessment on the basis of ST deviation

ST segment deviation in different leads can be used to estimate the extent of risk to the compromised region of the myocardium and consequently can be used to identify patients requiring urgent intervention.

Two methods of risk assessment using ST deviation are described below.

Method 1: Using the sum of the amplitudes of the ST-deviation in the 6 limb leads and 6 precordial leads.

As this sum increases, the risk to the compromised region of the myocardium increases.

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A cumulative ST deviation of 12 mm or more is an indication for urgent intervention. However, since the extent of ST deviation during ischemia fluctuates considerably, a single ECG tracing may not represent a reliable picture of the degree of ischemia in many cases. Because of this limitation, the method below is much preferred.

Method 2: ST-segment deviation vector (Ischemia Vector)

The ST-segment deviation vector is the vector that represents the ischemic region. In this method, the graphical representation of the leads is used to determine which areas of the myocardium are at risk. Moreover, the ST-segment deviation vector may also be useful in determining the specific site of occlusion in the culprit coronary artery. The use of the ST-segment deviation vector is further described in the subsections below.


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