When you're working down in the 70 range, you are putting a fair effort into the pedals. As you get above 80, you start to replace leg effort for leg speed. Until you're used to riding the higher revs and until you have a reasonable level of bike fitness, the higher revs will raise your heart rate (and with it, your breathing) but you'll put less stress on your body.
I'm no pro athlete by any means (50, over 105kg, fitter than six months ago but let's just say that's a relative judgement

) and I make the above comments based on my own experience, not on articles.
I now ride with a cadence in the 80's. It zips higher from time to time and sometimes, it's appropriate to keep it higher - I climb with a cadence of 90 because that's where I convert the most power into useful work.
It appears that your 'natural' cadence drops as you get older. I started by aiming for 90. That required a fair bit of careful cadence watching on my part and some rides designed specially to train my legs to work at those speeds. Once I was able to spin freely throughout the ride, I started to let my legs decide where they wanted to work rather than 'watch the clock'. As a result, I now work in the eighties.
As my cadence drops out of the eighties, the effort required to ride goes up noticeably. In the old days, I would have welcomed that because it felt like I was working. It's a false impression - okay, it's accurate because you are working, but you are working harder than you have to. I also find that I start to get sore knees and muscle pain if I let things mope about in the seventies.
When you get tired, letting your cadence drop is very seductive but again, it's a false impression because you working harder. By choosing a gear that allows you to spin in the eighties (totally ignoring bike speed), you will in fact, go further and often recover while on the bike. Hell, I can now recover while climbing hills if I have a low enough gear to use.
I use a HRM. My max HR is 185. If I ride with a HR of 140, I can go miles - recently did a century and a large part of that success was carefully controlling that HR. For a more intense workout, such as my 30km rides while the lad's at soccer training, I run my HR around 150 - 160 and get back the car swathed in sweat and feeling comfortably tired. Recovery rides are great and I'll do them at HRs below 120.
I control my HR using my gears. I keep the cadence up, but if the HR goes too high, I drop a gear or two and let the bike speed drop. On a long ride, where I'm tiring towards the end, my bike speed will drop as I come down through the gears. I've actually got quite good control over my HR now - if I'm aiming at 140 and it runs up to 145, down one gear will see the HR back to 140 very soon.
BUT, the numbers are just that, numbers. The above sounds like I'm ruled by the computer but in reality, I'm not. I use it as a guide. It has proven a great boon in helping me understand my body because many of the signals your body sends you are subtle and the 'thing that goes beep ... too flamin' often' tells you what those signals actually mean.
Of course, I also ride a fixed gear bike ... where you've go no control over cadence, HR or indeed much esle. When the road starts going up, you have to fight it because you can't change down a gear. When the road goes down, your legs are forced to spin with the pedals (a cadence of 140 is fun ... except when you're knackered from climbing up the other side of the hill you're now rolling down

). On those rides, the HRM sits in my back pocket (because I've only got a basic computer on the fixie), quietly recording the numbers so I can scare myself later - because there's only one gear, you can easily calculate your average and max cadence.
Richard