Dear Ken,
You ask an interesting question for which we don't completely have the answer. Your son has two issues, actually; he has a coarcation of the aorta, which was repaired and then subsequently stented, and he has a bicuspid aortic valve with reportedly mild dilation. We know that the transmission of the pulse wave of blood down the aorta after coarctation repair (and especially with a stent in place) is abnormal, making the aorta seem somewhat more stiff. We also think that isometric activity in patients with coarctation with persistent hypertension is not good. Overall, as you state, the amount of static, or isometric, activity needed to pitch is low, so that's probably fine. The main issues, then, are his blood pressure response to exercise, the amount of aortic dilation (which I cannot tell officially without seeing him), and also how much OTHER exercise he does. If his blood pressure response to exercise is normal, he should be okay from a dynamic standpoint. However, if he is playing competitively, the question is whether he is weightlifting as part of his training. If he is, he should be doing low weights/high repetitions to limit his isometric work. In the end, though, we have very little data to say what really should or shouldn't be done with these patients. These are just attempting to connect the few dots that we have to make a (vaguely) educated decision.
Thank you for your reply and the information you provided.
I did not mean to imply that I knew "the amount of static, or isometric, activity needed to pitch is low". I don't know, and that is what lead to my central question: just where does baseball pitching lie along the low-to-high spectrum of isometric sports activity? So I gather you think it is on the low side?
My son's cardiologist has also stated my son's athletic restriction in a somewhat different manner: i.e. no activity that leads to significant muscle building. And that statement is what lead me to consider the position of "pitching" separate from "baseball" in general, because pitching competitively for more than a couple of innings takes quite a bit of strength and stamina in the legs and back, more so than any other baseball activity. That strength and stamina must come from some level of muscle building during bullpen training or during the course of pitching in the games themselves. That said, pitchers don't typically have the exagerated back muscles of weightlifters nor the exagerated leg muscles of speed skaters (for instance). So again, I'm not sure how to classify "pitching" relative to this "muscle building" restriction. There is much dynamism in pitching, but there is also the need for strength and stamina.
Although my son's cardiologist has restricted him from weightlifting, the cardiologist has cleared him for push ups and sit ups. This clearance was based on the low to moderate weight involved in these exercises. And this seems to coincide with your advice to use "low weights/high repetitions to limit his isometric work". Thank you.