Hello, Welcome to HCM. It is highly unlikely that severe constipation may cause irregular heart beats but yes,on few occasions it may cause rise in blood pressure due to continuous straining at stools. Also,let me know how you come to know about irregular heart beats or if you have gone to ER for EKG and the doctor have diagnosed it. As you had a mild heart attack previously in March,so I would advise to avoid straining at stools.Or doing so may cause exaggeration of cardiac problems. If you have constipation with hard stool, you should take plenty of water, foods like vegetables, fruits, and leafy vegetables on every day as it will make stool bulky and soft by retaining water in it leading to easy passage of stool. And make a habit of going to toilet everyday as if you skip one day the retained stool becomes hard on the next day. Even after trying this if you still have difficulty in passing stool you can take stool softeners like oral lactulose or syrup cremafin plus 3TSF daily at the bedtime after consulting your Physician. Hope this detailed information will help. Regards,