https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3370379/

Acute myocarditis mostly does not sufficiently respond to symptomatic medication for heart failure, and mortality is high in spite of treatment. The long-term disease course depends on the pathogen, the extent and type of inflammation, and the initial injury to the myocardium. Focal borderline myocarditis often undergoes spontaneous clinical healing if no serious heart failure developed initially. The early mortality of fulminant lymphocytic myocarditis requiring intensive care is in excess of 40% in the first 4 weeks (7). Untreated giant cell and eosinophilic myocarditis also have an extremely poor prognosis, with 4 year survival rates of less than 20% (8). Granulomatous necrotizing myocarditis is lethal if overlooked and untreated. Non-fulminant active myocarditis has a mortality rate of 25% to 56% within 3 to 10 years, owing to progressive heart failure and sudden cardiac death, especially if symptomatic heart failure manifests early on (9– 11, e1). In addition to impaired left ventricular (LV) and right ventricular (RV) function, virus persistence, chronic inflammation, and cardiodepressive autoantibodies are independent predictors of a poor prognosis (9, 12, 13).

First study I found on duckduckgo. 56% is a simplification, but is fairly accurate as internet talking points go. Some diseases that cause myocarditis don't do as much damage, but the viruses that do tend to do the most. The vaccine, with it's graphene nanoparticles (contamination?) and viral spike protein factory cells could in fact be far worse than other know causes of myocarditis, but that is not known yet. The important thing to know is that a large number of people die within weeks of myocaritis and everyone who survives, survives with damaged hearts that don't heal. Longterm survival is basically reliant on how much damage and if the person can get away with basically not exerting themselves or increasing their heart rate for the rest of their lives.