19 Yrs Ago Had A Triple Bypass And Was Put

19 yrs ago had a triple bypass and was put on lopressor 25 mg a day. im 82 yomale. lately been getting liVERY lightheaded. bp low 80/50 p60 never had hi bp usually 120/50 told my cadiologist about this and he said eat more salt' when to family dr and he said cut it in half once a day. what should i watch for or is the dose low so it should go ok.