Two South Florida hospitals paid millions in fines this week to settle charges that they filed false claims with Medicare for implanting cardiac devices in patients during a waiting period when doctors are supposed to hold off and see if the patients recover on their own. Mount Sinai Medical Center in Miami Beach and Cleveland Clinic Florida in Weston were among 51 hospitals nationwide to pay more than $23 million in fines, closing a sweeping federal investigation into hundreds of hospitals for improperly billing Medicare for implantable cardioverter defibrillators or ICDs.