while it's possible for people to experience muscle stimulation from pacemakers it's typically the diaphragm as it lies close the the right ventricle which is actually being paced. while i can't diagnose the cause of your muscle twitching in this forum i would guess that left pectoralis stimulation would be pretty unlikely particularly if it doesn't seem related to your heart rate. always helpful to get checked out by your doctor if you have any concerns.
can pacemaker lead cause a chest muscle twitch. i have a st jude pacemaker and lift weights. i just started getting a muscle twitch in my left pectorail muscle. it is very random and it doesn't seem to affect my heart rate. is this common or should i have it checked?