Is weed grit a cause of pericarditis?

Not likely. Pericarditis is an inflammation of the pericardium usually caused by infection, underlying cardiac disease, or autoimmune diseases. Grit weed has particles of sand or glass added for weight. Inhaling them may increase respiratory problems, but there is no report yet that it can cause pericarditis. If the weed is contaminated with an infective agent, then it could cause pericarditis indirectly.