Hiatal hernia is of various types.
The most common type, sliding type, would not likely cause effect on heart unless it got significantly large in size. Hiatal hernia is after all in the chest, and alrge one could potentially apply pressure on heart. Death due to sliding type would be unusual. On the other hand, the less common type known as paraesophageal hernia can get twisted in the chest and can create an emergent situation and even death. Your doctor is the best judge.