how many interruption vena cava procedures were done until 3 years ago in total?
select count(*) from procedures_icd where procedures_icd.icd9_code = ( select d_icd_procedures.icd9_code from d_icd_procedures where d_icd_procedures.short_title = 'interruption vena cava' ) and datetime(procedures_icd.charttime) <= datetime(current_time,'-3 year')