Thanks, folks. Thinking it over, I've been down the beta-blocker/vasodilator lane before, and while it was at times very disagreeable on the hills I did get up them. The main difference is that this time the stenosis can't be stented without blocking off a subsidiary network, so that I'll just have to ride with it and hope.
E-bikes are becoming common here. Several times recently I've gasped up hills only to see very unathletic-looking types cruising up ahead, sitting upright and putting no visible effort into it. Galling, that.