Limiting exerciser is standard advice with aortic valve problems, for the simple reason it is often necessary.
Having thought about it, any prescribed limit will be a little arbitrary.
I wonder if something like Staley’s Escalating Density Training (EDT) would allow for more control. The idea is you do a 1-3 pairs of exercises for many sets at easy weights, say 50%. Because of this, it is easy to stop when a parameter like heart rate is too high. But still get a very good workout in that boosts strength and hypertrophy.