Prolonged constipation may cause you to strain and overexert yourself in the bathroom. It can trigger a fatal heart arrhythmia in some people. This happens because as you bear down while holding your breath, it triggers a nerve in your chest that sends a message to your brain that triggers a change in heart rate and blood pressure. Eventually, your blood pressure decreases after 5-7 seconds
When this happens, your body gets confused and tries to correct it, but sometimes it over-corrects. This over-correction can throw off your heart rhythm, skyrocket your blood pressure, and trigger a heart arrhythmia. Some say this is what happened to Elvis when he died!
There are other cases of chronic constipation that led to bowel perforation, exacerbated other illnesses, and led to death. However, keep in mind that this tends to happen mostly in the elderly and those with pre-existing heart conditions.
It can happen for a plethora of reasons. You may not be drinking enough water or getting enough fiber in your diet. You may get it from overloading on too many dairy products or from too much stress. There are also many medications, including strong pain medicines or iron pills, that can trigger constipation.