tailieunhanh - MEDICINE HURST VENTRICULAR ELECTROCARDIOGRAPHY - Part 3

Lưu ý rằng trường điện chia ngực thành hai nửa; điện tích âm sẽ được ghi lại từ nửa bên phải và điện tích dương sẽ được ghi lại từ bên trái. Khi điều này xảy ra, dẫn độ võng ghi V1 và V2 tiêu cực, dẫn hồ sơ V3 lệch một chút tiêu cực, và dẫn V4, V5, V6 ghi lại độ võng tích cực. | 57 Figure illustrates the type of deflection that would be recorded at positions V1 V2 V3 V4 V5 and V6. Note that the electrical field divides the thorax into two halves negative charges will be recorded from the right half and positive charges will be recorded from the left. When this occurs leads V1 and V2 record negative deflections lead V3 records a slightly negative deflection and leads V4 V5 and V6 record positive deflections. One can see how a plane that is perpendicular to the arrow intersects the surface of the chest and divides the thorax into two halves. In this case the transitional pathway passes between leads V3 and V4 it is slightly negative but smallest in lead V3 . The vector is directed about 35 posteriorly. Observations such as those illustrated in Figure lead to the formulation of the following rule whenever an electrical force represented as a vector is perpendicular to a precordial lead axis it will project. its smallest shadow on that axis and the electrocardiograph machine will write its smallest deflection on that lead. A vector representing such an electrical force will be directed toward the area of the chest where the precordial electrodes record upright deflections. It is not possible to state as was the case with the extremity leads that whenever an electrical force represented as a vector is parallel to a precordial lead axis it will project its largest shadow and therefore record its largest deflection on that lead axis. This is because some of the precordial electrode positions especially V1 V2 V3 and V3R are nearer the heart than the others and would record larger deflections the precordial electrodes are not electrically equidistant from the heart. Therefore to restate the situation one can assume that when an electrical force is perpendicular to a precordial lead axis the electrocardiograph machine will write its smallest deflection on that lead but one cannot assume that an electrical force parallel to a precordial .