This is the term used to describe the contraction of the heart.

这是用来描述心脏术语。

This is a term used to describe the contraction of the heart.

这是一个用来描述心脏术语。

That is reassuring. But what about the other bad beats, the premature contractions in the heart's lower chambers?

这就让人放心了。那其他有害心跳，发生在心脏下腔期前(室性期前)呢?

On rare occasions, a sudden change in heart rhythm prevents the upper chambers of the heart from contracting normally.

在极少数情况下，心律突然变化会阻止心脏上腔正常。

Frank and Starling were looking at the amount of blood in the heart before the ventricles contract.

Frank 和Starling正在观察心室前心脏血流量。

It would squeeze the capsule tightly as the heart contracted and still keep a firm grip on it when the heart was relaxed.

它可以随着心脏微挤压胶囊，且在心脏放松时，也能紧紧抓住。

This ability is thanks to the intrinsic conduction system, which is the internal regulating system that causes the heart to contract rhythmically.

这种能力是由于内在传导系统，这是导致心脏有节奏内部调节系统。

This ability is thanks to the intrinsic conduction system, which is defined as the internal regulating system that causes the heart to contract rhythmically.

这种能力归功于内在传导系统，内在传导系统被定义为使心脏有节奏地内部调节系统。

That's right - a healthy heart does not pump every last drop of blood out of the ventricles when they contract no matter how strongly they contract.

没错，一个健康心脏在时候不会把每一滴血从心室中泵出，不管多厉害。

However because calcium is also involved in cardiac myocyte contraction, these agents also reduce contractility of the heart and should not be used in case of systolic heart failures.

然而，因为钙通道也参与了心肌，所以这些药物也会减弱心脏力，因此性心力衰竭患者不应该使用该类药物。