Back in 2011 my daugher, who was nine years old at the time, got a mechanical mitral valve. Post-surgery, her cardiologist put her on a daily aspirin in addition to the warfarin. A year later she started having terrible stomach issues, which got so bad that she was frequently vomiting throughout the day and especially after eating. I questioned the cardiologist whether it could be the result of irritation to the stomach lining from the aspirin and told him I wanted to stop it, and he agreed. However, it took multiple diagnostic test and several months before her stomach issues resolved once the aspirin was stopped. I can't be sure the gastritis was caused by the aspirin, but she has not had issues like that since.