Why is that?

为什么会这样
Because your heart is oriented in space,

因为你的心是立体的
it's a three dimensional object.

它是一个三维对象
All of these cells are at particular three-dimensional positions

这些细胞都在这个三维物体内部的
inside this three dimensional object.

特定的三维位置上
As these currents happen they happen in a very spatially oriented way.

由于这些电流以一个非常注重空间的方式发生
So,the potential difference I measure at a distance,

所以我可以测量两点间的电位差
here and here for example,is different.

比如从这儿到这里是不一样的
It's sort of like looking at the heart from different vantage points,

这有点像在从不同角度观察心脏
looking at the electrical activity of the heart

从不同位置
from different vantage points.

观察心电活动
One of the things that cardiologists have learned how to do

心脏科医师们已经掌握如何