when was the last time that patient 18159 had 2 int mam-cor art bypass's since 2101?
select procedures_icd.charttime from procedures_icd where procedures_icd.icd9_code = ( select d_icd_procedures.icd9_code from d_icd_procedures where d_icd_procedures.short_title = '2 int mam-cor art bypass' ) and procedures_icd.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 18159 ) and strftime('%y',procedures_icd.charttime) >= '2101' order by procedures_icd.charttime desc limit 1