My BP was 90/60 during my youth. At night I would often have a resting pulse of 40. This was said by the doctor that it indicated excellent health, a good heart because of the exercise I had done. But it made me tired, and it was suggested I eat more salt to raise my BP. I did not have an MS dx, although it was suspected because of the family connection to MS. However, no dx until AFTER my BP went UP.

In middle age, my BP went up a lot, to about 140/90. The doctor didn't take that very seriously, saying it was the stress of work and I could go on a low salt diet and fix it.
I told the nurse that I suspected that the doctor did not take my situation seriously because I was a woman, a mere woman. The nurse smiled knowingly, and kept smiling a lot more when I saw her in the hall of the clinic (UW Hospital clinic).

Anyway, the low salt diet caused me to nearly pass out several times, and my husband had to rescue me, leave his work to gather me from wherever I nearly passed out. This continued, but finally my neurological status was bad enough so I had Optic Neuritis and got a DX through several tests.

My BP is now wonderfully normal except when I have an "attack". By attack I mean an attack of any of my three diseases which affect my neurological status. Then it can go up alarmingly. I regulate my tendency to get a fast pulse with a low dose of Propanalol, but a-fib can rear its ugly head.

The only time in recent years I have had a too low pulse was when I took a bad medication. Bad for me. The recent culprits have been chemotherapy for high platelets.
Hydrox-Urea and Interferon and Angrelide. All ER level situations. I had to take radiation to lower my platelets, which worked without side effects, but it is dangerous in that 10% or so can get leukemia a few years later, but they say I'm old enough so that won't matter.