CREATE TABLE table_204_597 (id NUMBER, "main author" CLOB, "no. of patients" NUMBER, "duration of follow-up years" NUMBER, "linearized rate of infection" CLOB, "actuarial freedom from infective endocarditis" CLOB)

how long was the duration of follow up for revuelta ?
SELECT "duration of follow-up years" FROM table_204_597 WHERE "main author" = 'revuelta'
SELECT "duration of follow-up years" FROM "table_204_597" WHERE "main author" = 'revuelta'