I am not aware of any human trials on cannabis due to it's schedule 1 status - no recognized medical benefits. Do you have a source to cite? Was it outside the US?
Unfortunately I could only give you abstracts right now--and they're not the ones that I looked at. I don't currently have at-home access to the university servers which is where I found most of this info.
What I can tell you:
1. I'm not blowing smoke up your ass.
2. There have been plenty of human trials.
3. Recent ones have been out of country for the most part (but not all)
4. These were effects well understood as early as the 60's and 70's during which there were quite a few human trials performed here in the US.
Most of the new research builds off the research from the 70's and simply added in various drugs to see what what was antagonizing the cardiovascular effects. IE, are they alleviated by atropine/propranolol/etc. This gives them an idea of what receptor is being acted on by the stuff.
Furthermore, again I can't find them right now, but there are a myriad of effects on lipid synthesis, lipid storage and transport, and other lipid-y stuff--which also have implications for cardiovascular health (and might be a mediating factor in some of the observed BP issues).
Here's an example of a 1979 article which covered human trials:
http://link.springer.com/article/10.1007/BF00426733
You'll notice it discusses "characteristic tachycardia" in the abstract. As I've said this is a well understood and established effect of the drug in humans--this language echoes that. The data would do the same if we had access to the article.
It's a pretty marked effect, so it's not some tiny percentage fraction. We're talking taking resting heart rate from 70 to above 100. Not a statistically tiny result by any stretch.
Here's a more recent study covering some effects relating to abrupt cessation that are pretty striking:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3045206/
Here's an example of US human trials taking place in 1992:
What you commonly hear is that there is no research being done because it's schedule 1. That's not precisely true. There isn't a great deal of research being done to determine medically beneficial effects--but there's actually quite a lot of data out there on the ill effects.
A case study:
A meta analysis published in 2007:
http://www.sciencedirect.com/science/article/pii/S0167527306007789
and so on. This is just what I can find in google--which is a really terrible tool for doing this type of research. If I had access to the university I could literally pull up journal after journal after journal.
Ultimately what is clear is that there are serious and lasting physiological effects related to smoking.
That certainly doesn't mean the stuff should be illegal, but we should also not be willfully ignorant of this. It's also not proper to discuss cannabis as though there are no ill effects. It's just not true.
There are no particularly acute ill effects at typical dosages--but that's a far stretch from it can never hurt you ever, and that's what most people are walking around saying to people and believing themselves. Hell I'm currently dealing with a lot of cardiovascular issues myself, and the doctors can't figure it out.
I wouldn't be the slightest bit surprised to find out it has something to do with me smoking pot all day every day since the age of 13. Not even slightly surprised. I love my pot, though, so I probably won't let that sway me still :)
Obviously this ignorance hurts the legitimacy of the movement--because in essence the people carrying the flag don't know what the hell they're talking about. If you want to be taken seriously you must protect your credibility like it's all that you have (because it is).
Our "lobby" if we can call it that has been bleeding this credibility for most of the push for legalization over the last 15ish years--almost totally unbenknownst to them unfortunately.