Medrano G A, de Micheli A
Prensa Med Mex. 1979 Nov-Dec;44(11-12):234-41.
In the presence of low right atrial rhythms, the eight-shaped PF loop is located in the first quadrant, the PH loop is rotating in a counterclockwise direction and PS can rotate in either course. When the rhythm originates in high left atrial regions, PF and PH loop loops can be found in the third quadrant of both planes and should have a clockwise rotation. When the pacemaker is located in low left atrial regions, the PF loop rotates in a counterclockwise direction, or with its branches superposed, and located in the second quadrant; PH is rotating clockwise in the third quadrant; PS with either a clockwise or a counterclockwise rotation, is situated above and slightly ahead of the E point. In the presence of a nodal rhythm, the P loops show a counterclockwise rotation or an eight-shaped configuration. In the absence of atrial enlargements, the PF loop can be seen in the first quadrant and the PH in the first or the fourth quadrant.
在右心房低位节律存在时，“8”字形PF环位于第一象限，PH环呈逆时针方向旋转，PS可沿任一方向旋转。当节律起源于左心房高位区域时，PF环和PH环可在两个平面的第三象限发现，且应呈顺时针旋转。当起搏器位于左心房低位区域时，PF环呈逆时针方向旋转，或其分支重叠，位于第二象限；PH在第三象限呈顺时针旋转；PS呈顺时针或逆时针旋转，位于E点上方且略靠前。在存在结性节律时，P环呈逆时针旋转或“8”字形形态。在无心房扩大的情况下，PF环可见于第一象限，PH环可见于第一或第四象限。
