Headlines in the United States tell of bitter political polarization. Take gun control, for instance. Mass shootings have become all too common, followed by news stories that imply that reform efforts ...

It's no secret that we live in a polarized world. Even if you ignore politics (good luck trying that), you'd also have to ignore entertainment news (exes or coworkers squabbling), sports news ...

The PR interval is the time from the beginning of the P wave (atrial depolarization) to the beginning of the QRS complex (ventricular depolarization). The normal PR interval measures 0.12-0.20 ...