Vienna has correctly and fully defined the expectations, but I would add that it is critical for a successful outcome in the long term is to have received oxygen quickly as the longer the heart is deprived of oxygenated blood (happens when the heart stops beating) the more severe the heart cell damage and a weaker heart (impaired contractions).
I was hospitalized for 5 days for heart failure, and 7 days is not unusual and if anything it is a bit too long for a very young person. Because of the age it is likely not vascular from any blockage, and more likely arrhythmia (irregular heartbeats).
"Patients who survive cardiac arrest without irreversible damage to their central nervous systems will likely undergo extensive diagnostic and therapeutic testing, including cardiac catheterization and/or an electrophysiology study. If they have underlying heart disease, such as coronary artery disease, this will likely be aggressively managed with medications and lifestyle changes. In addition, many patients may have an implantable cardioverter defibrillator implanted during their hospitalization. This device monitors the heart rhythm and, in the case of a serious arrhythmia, delivers a shock that jolts the heart back into a normal rhythm. These devices can be combined with pacemakers."
If he had cardiac arrest , yes it could take 7 or more days.
Different hospitals, different cases, hard to know or say.
I had heart failure and was in the hospital for 12 days, some people in more or less.
Good luck with your trust issue. Long distance relationship can not work without trust.