If people reinfected with the coronavirus COVID-19 have a 10% chance of serious cardiac complications, will the odds of this serious complication be even higher if another reinfection occurs?

Unfortunately, this is true as well. Not only will people be fully susceptible to reinfection with mutant strains developing among the population and circulating to and fro, once they have been infected and tissue damage results, a second, and a third, and a fourth reinfection will add to the damage and this will move towards serious complications at some point, and these serious complications will recur from that point on and worsen still. There is only so much beating a body can stand, particularly when the kind of impairment is to some degree a loss of function. Eventually, the strain becomes too much and a fatal infection will be the end point.