Is it permissible for a chronic heart patient, who needs to drink a large amount of water daily, to break their fast in Ramadan when the days are long and hot, given the possibility of making up for it on shorter days, or fasting one day and skipping one?

Fasting Ramadan is obligatory for those who are able to do so, and it is permissible for those who are harmed by it to break their fast. So, whoever is able to fast some days without harm should do so, and they must make up the days they missed if they can do so on short days. If they are completely unable to make up the fast, then they must feed one poor person for each day.