Necessary for hiking? Not so much. But one way to test cardiovascular strength is the VO2 "Max" test.
VO2 stands for volume of oxygen consumed, and is generally measured in liters per minute (L/min) and also scaled for different bodyweights (mL/min/kg). That is, the amount of oxygen that your heart can pump to your muscles. One can say that the larger the value, the better cardiovascular shape you are in, as your heart can pump more oxygen and so you can perform more work during exercise (move faster).
The test generally lasts from 10 - 15 minutes, and works by increasing the workload each minute. In my case, the grade was set at 14%, and the speed was increased 0.5 mph each minute until failure. I think I failed at about 7 - 7.5 mph. The clip only shows the end of the test.
There are plenty of specifics one could talk about in regards to exercise performance - such as the applicability of such a test versus a lactate threshold test, which I will discuss in the future. Just keep in mind that getting a high maximum output does not mean that you can sustain a high level for a long period of time. That is a more important, and stronger indicator your endurance capacity.
How it Relates to Hiking:
VO2 max is tested a lot in runners, cyclists, cross-country skiers...but hikers may encounter similar endurance tasks. A nonstop effort of Iron Mountain can be quicker if you can pump more oxygen. Or, for a given pace, it will feel easier. More on training for this sort of thing later.
Max VO2 (L/min): 5.4
Max heartrate: 194
Don't try to max out while hiking!