1)A resting heart rate of 170 is rarely normal nor healthy on stimulants. You may want to look into seeing a doctor and getting some basic cardiovascular tests done to determine whether you may have an underlying cause for this drastic spike in heart rate. It could save your life.
2)Anxiety can really increase blood pressure and heart rate while under the influence of a stimulant by quite considerable amount. If you are experiencing panic attacks from a serotonigenic substance like MDPV, then it would be best to take a long break(2 months) for your brain to up regulate the pleasure receptors involved in MDPV's method of action.
3)Benzodiazepines will most likely be administered to you intravenously upon entering a hospital if you consult an ER about having an overdose. Benzodiazepines will lower heart rate, blood pressure and put the "Brakes" on the MDPV which is what is causing your CNS to speed up out of control. Benzos like Lorazepam, Diazepam, Alprozolam and Clonazepam work wonders for reducing anxiety. However they will nullify a large majority of the pleasure you experience.