when was the first time the heart rate measured in patient 13703 until 08/24/2102?
select chartevents.charttime from chartevents where chartevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 13703 ) ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'heart rate' and d_items.linksto = 'chartevents' ) and strftime('%y-%m-%d',chartevents.charttime) <= '2102-08-24' order by chartevents.charttime asc limit 1