How low is too low regarding heart rate??

I am a 63 year old man.  I have had sinus tachycardia many times in my life, and a heart rate too fast.  Now, my heart rate seems to have gone the other way.  I took a high rate of Effexor XR for many years and try to taper it down from 450 mg to 300 meg per day.  But now, my heart rate goes low.  My BP is basically ok, but it has also gone low before too, once down to like 98 / 45.  

I have also had many PVC's in the past, but now I don't have them.  It seems that when I drink caffine drinks, then I get them and it takes a month or so for them to go away once I start having them.

What are my risks... is this something that will kill me?  I am also a mental patient.  The problem is worse when I combine the effexor xr and vicodin... for a back pain chronic from inoperable condition in L4-L5 after a car accident.

Thanks...

[Brooke_38]

You didn't say how low your heart rate was. Are you having any associated symptoms like dizziness, fainting, fatigue?

You should be careful mixing effexor with vicodin as taking both will increase side effects.

Outside of the sinus tach, do you have any other cardiac related problems?