instruction: how many patients since 1 year ago received opn aortic valvuloplasty two times?
response: SELECT COUNT(DISTINCT t1.subject_id) FROM (SELECT admissions.subject_id, COUNT(*) AS c1 FROM procedures_icd JOIN admissions ON procedures_icd.hadm_id = admissions.hadm_id WHERE procedures_icd.icd9_code = (SELECT d_icd_procedures.icd9_code FROM d_icd_procedures WHERE d_icd_procedures.short_title = 'opn aortic valvuloplasty') AND DATETIME(procedures_icd.charttime) >= DATETIME(CURRENT_TIME(), '-1 year') GROUP BY admissions.subject_id) AS t1 WHERE t1.c1 = 2