Can the mileage to and from the cardiac rehabilitation be included as a "medical expense" for tax purposes?

Actually, geewiz is right about the 10% - it applies to everyone starting with the 2017 tax year. But most people are dealing with the 2016 tax year right now, for which the old 7.5% rule still applies for people 65 and older.

Yes, see Irsdotgov topic 502. For 2017 only medical expenses that exceed 10% of your adjusted gross income qualify for a deduction on your itemized deduction page. That is a fairly high bar for most of us to reach.

I agree with geewiz, except that if you're 65 or over, the old 7.5% floor stays in effect. Also you need to be careful whose return you're talking about. You can't claim your parent's expenses on your return unless you're claiming them as a dependent, which in general requires that you provide over half of their support.

And it really is quite a high bar to reach. The few times I've seen it were with people paying for their own insurance, who had significant expenses on top of that. Insurance alone can come close to consuming 10% of one's income, assuming you're not receiving Medicare.

and if the patient is your spouse - not yet 65??? The cardiac rehabilitation requires a lot of extra visits and time off work (meaning lower salary/FMLA leave). What do I need to do to prepare for the 2017 taxes. This second job literally began Jan of 2017.

Well, if the patient is your spouse and you're filing jointly, there's no question of whether you can claim them as a dependent. The 10% floor applies to your joint income. As far as planning, I can only say to keep records and receipts so you don't have to recreate too much at tax time.