Complex sentence: Stress is the main factor in takotsubo cardiomyopathy, over 85% of cases are set in motion by either a physically or emotionally stressful event that prefaces the start of symptoms.
Split into simpler sentences: Stress is the main factor in takotsubo cardiomyopathy. Over 85% of cases that deal with broken heart syndrome are set in motion by either a physically or emotionally stressful event that prefaces the start of symptoms.