Wierse, was this prescribed cardiac rehab for you or for someone else. For yourself you can deduct mileage depending on how much out of pocket cost you have had for medical throughout the year. As for deducting because you are driving someone else, you'll have to check with an accountant/CPA. Or check the IRS website.
Business 56 cents/mile
Charitable 14 cents/mile
Medical and moving 23.5 cents/mile