I think "OHS" is a smidge of a misnomer, the way we typically use it. Maybe we should all switch to "OCS" = Open Chest Surgery, which is what I think we mean most of the time. Any time a chest is cracked open and the heart is exposed to air and bright lights is "OHS" in my books. The minimally invasive and robotic options are still variations on OHS in my mind, even though they are relatively common in some centers.
The competition/choice between the various general options, and the regional (and chronological) variations in their use, is a fascinating topic for us, and maybe for some other students of medicine and history. Of course, the choices change depending on exactly what has to be done to the heart, but speaking generally:
When minimally invasive heart surgery was first developed, I think it looked like the obvious way of the future. It increased fairly fast from zero, but I think its progress has been very slow or "sideways" or possibly even "backwards" in recent years. I see it partly as a conflict between the convenience of the patient (smaller scars are always better, and a cracked sternum is a negative, so avoiding it is a Good Thing) versus the convenience of the surgeon (getting better access to your "workplace" is a Good Thing, and learning new and tricky techniques is mostly a negative, as are having occasionally to switch approaches mid-surgery, or God Forbid losing a patient or compromising a patient's clinical outcome).
I think it's also partly a conflict between "the best" and "what works well", or "the good enough" -- and between the novel and the tried and true. There are SO MANY things that have to go right for a heart-valve op to be a complete success (and so many possible "bumps" on the recovery road), that even many World-Class surgeons don't consider it worthwhile to risk their great track record (and the benefits it gives their patients) by "changing their game", in return for benefits that are mostly either cosmetic or "convenience" (like being able to lift 30-pound objects a month sooner post-op. That group of World-Class surgeons includes mine and his colleagues -- surgeons who invented and pioneered many important and revolutionary surgical breakthroughs, including "The David Procedure" and the "Simplici-T" ring for MV repairs, etc. These people aren't shy about trying new things that are necessary to save a life, or to restore good quality of life, or to maximize the odds that a patient will be healthy and fit. But my guy was very clear about how uncomfortable he is whenever he performs minimally-invasive heart surgery -- uncomfortable mostly because he's unusually nervous that the surgery won't go well. Maybe that discomfort is mostly because they only DO minimally-invasive heart surgery rarely and under duress, like for young "babes" who REALLY don't want a sternotomy scar added to their décolletage. I.e., maybe they'd become comfortable if they just DID the M-I approach more, maybe first "interning" in a place where they are the standard approach. But what they're doing NOW is working so well, they get to use phrases like "Gold Standard" in the titles of their peer-reviewed articles, so should they really be downplaying the surgical approach that works that well, in favor of one that MAY (or may not) ever be quite that successful? There are some good reasons and some less-good reasons not to change.
I don't have the answer, partly because I don't know whether the results will ever be as good as Dr. David's and Dr. Feindel's in terms of cardiac outcomes. I've also found my sternotomy to be a relatively short-lived and painless nuisance, and my scar isn't going to change my life, either. (I'm planning to spend next week skiing downhill at Whistler, 8-9 weeks post-OHS, and my still-healing sternum is probably THIRD on my list of new post-OHS worries, AFTER my still-weird heart function, my ACT/Warfarin/Coumadin [My cardiologist thinks that NOBODY who's on ACT should EVER ski downhill!], and only THEN my sternum. I'm adding a heart-rate monitor AND a helmet AND some chest padding to my ski gear, to try to minimize those worries.)
So I wasn't crushed when I found out that Dr. Feindel really did NOT want to do my surgery minimally-invasively, and I stuck with him and his team, and I still don't regret that choice. Somewhere there's a parallel universe, where I went to Ottawa or Manhattan to get the job done through a much smaller opening, or two or three -- but not in this universe, and that's OK with me. Interesting issue, though.