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MEDICINE HURST VENTRICULAR ELECTROCARDIOGRAPHY - Part 7

Đặc điểm của khối còn lại Bộ phận Posterior-kém • • Thời gian QRS là 0,9-0,11 giây, nó thường là 0,10 thứ hai. Vector QRS có nghĩa là hướng về 120 ° bên phải và hơi phía sau .* Một điện trước đó không hiển thị vector QRS có nghĩa là hướng bên phải. Nếu không có điều này, nó là không xác định được khối này. | 169 identify the true cause of the left axis deviation of the mean QRS vector. Table 8.9 Electrocardiographic Characteristics of Left Posterior-Inferior Division Block The QRS duration is 0.9 to 0.11 second it is usually 0.10 second. The mean QRS vector is directed about 120 to the right and slightly posteriorly. A previous electrocardiogram that does not show the mean QRS vector directed to the right. Without this it is impossible to identify this block. Anterolateral infarction right ventricular hypertrophy acute and chronic cor pulmonale and emphysema can be excluded by other clinical methods. It is not possible to assign a precise number of degrees to the rightward direction of the mean QRS axis in order to identify the presence of left posterior-inferior division block. Some authors state that it should be 110 to the right and I have used 120 in this book. Table 8.10 Electrocardiographic Abnormalities That Must Be Differentiated From Those of Left Posterior-Inferior Division Block The tall thin normal adult may have a mean QRS vector that is directed vertically and posteriorly. On rare occasions it may be directed as much as 110 to 120 to the right. It may be impossible to distinguish this finding from the abnormality due to a posterior-inferior conduction defect. Myocardial infarction of the anterolateral ventricular wall may produce a QRS complex duration of 0.10 second and a mean QRS vector direction of 120 to the right and posteriorly. These are the salient features of right posterior-inferior division block. Other evidence of infarction ie abnormal ST and T vectors may be present to distinguish it. The duration of the mean QRS complex is 0.12 second or more as in right bundle branch block with the mean QRS vector directed to the right and anteriorly. Right ventricular hypertrophy may produce a mean QRS vector that is directed to the right and anteriorly but this may not arise early in its natural history when due to acquired disease in the adult. .