Question: Is it permissible for a person who has a heart disease to break his fast in case of feeling so tired in Ramadan?
Answer: A sick person who finds it hard to fast, either based on what a professional Muslim doctor tells him or because he feels unable to continue fasting, can break his fast. Allah the Almighty says: "but if any of you is ill or on a journey, the same number (should be made up) from other days." If the disease is chronic and not expected to recover, the person should pay fidya feeding a poor person for every day he didn't fast,  and if the illness is temporary, he should fast the same days after Ramdan.