My heart missed a beat. What could it mean?

我的心跳都停了。这是怎么回事？

Glancing up at Rick’s face, she felt her heart miss a beat.

【miss】抬头一看里克的脸，她感到自己的心脏都停跳了一拍。

His heart missed a beat as he saw the body of a small child at the water’s edge.

【heart】看到水边一具幼儿的尸体时，他心跳都停顿了一下。