Both your linked fact from the University of Arkansas
> When you sneeze, the intrathoracic pressure in your body momentarily increases. This will decrease the blood flow back to the heart. The _heart compensates_ for this by changing its regular heart beat momentarily to adjust. However, the **electrical activity of the heart does not stop** during the sneeze.
...as well as your 'myth' from webMD
> For instance, it's **_not true that your heart stops_** when you sneeze. When your chest contracts because of a sneeze, your blood flow is momentarily constricted as well. As a result, the rhythm of your heart may change, but it definitely doesn't stop.
...come to the **same conclusion** , namely the heart does not stop during a sneeze.