count the number of patients that are prescribed metoprolol tartrate in the same hospital encounter after having been diagnosed with abn react-cardiac cath until 3 years ago.
select count( distinct t1.subject_id ) from ( select admissions.subject_id, diagnoses_icd.charttime, admissions.hadm_id from diagnoses_icd join admissions on diagnoses_icd.hadm_id = admissions.hadm_id where diagnoses_icd.icd9_code = ( select d_icd_diagnoses.icd9_code from d_icd_diagnoses where d_icd_diagnoses.short_title = 'abn react-cardiac cath' ) and datetime(diagnoses_icd.charttime) <= datetime(current_time,'-3 year') ) as t1 join ( select admissions.subject_id, prescriptions.startdate, admissions.hadm_id from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where prescriptions.drug = 'metoprolol tartrate' and datetime(prescriptions.startdate) <= datetime(current_time,'-3 year') ) as t2 on t1.subject_id = t2.subject_id where t1.charttime < t2.startdate and t1.hadm_id = t2.hadm_id