She studied the blocked entrance and saw water tricklingin through the cracks.
她仔细观察了被堵塞的入口，发现水是从裂缝中慢慢渗透进来的。
英语百科
Parasystole
（重定向自Entrance block）
Parasystole is a kind of arrhythmia caused by the presence and function of a secondary pacemaker in the heart, which works in parallel with the SA node. Parasystolic pacemakers are protected from depolarization by the SA node by some kind of entrance block. This block can be complete or incomplete.