I don't believe taking such a comparatively low dose of Methylphenidate (Ritalin) would be enough to provoke any kind of serious physiological response. Anyone who would prescribe Methylphenidate would have at least a cursory knowledge of your medical history, which would include blood pressure history.
It's always riskier using stimulants when you have any kind of cardiovascular history, but that doesn't mean it can't be done. If you monitor yourself and use the medication responsibly i.e. as prescribed, I don't think it's contraindicated. This could change at any time, so like I said, always be monitoring yourself. If it is giving you anxiety, perhaps you could go buy a blood pressure cuff from the pharmacy or invest in a fitbit. This will give you pretty accurate readings for all of your cardiovascular indicators including pulse, blood pressure etc.