"Any existing pacemaker device would need to be placed on the...

"Any existing pacemaker device would need to be placed on the outside of the heart to be in the correct position and this is not feasible without open heart surgery."

Current leadless devices are designed for the right ventricle. No, it is not feasible to place them on the outside of the heart, not even with open heart surgery as they are not designed for that. Current CRT devices (which use leads) stimulate the left ventricle from the coronary sinus (which is on the outside of the heart but is accessed internally through the right atrium).

"The EBR device is much smaller and can be placed within the heart tissue area needed to pace the left ventricle by pushing it through from one of the right chambers of the heart with a catheter."

EBR's device is not 'pushed through' from the right chambers of the heart. It is deployed into the left ventricle by access of the arterial system. Yes you are correct that blood clotting on the left side can result in stroke, but the wise device endothelialises (~60 days) to minimise the risk of stroke.