Sorry to hear about that. Ephedrine is not my favorite drug, but it wouldnt be related to the pulmonary artery rupture. Ive seen it happen in a clinical setting from a connective tissue disorder where a component of the artery was genetically absent making it less strong than a normal person. It also can happen from sudden impact. Princess Diana died of a pulmonary artery rupture due to the car accident she was in. ALthough I agree that ephedrine can be dangerous and recommend not taking it, it is unlikely that it would weaken arterial integrity.
My condolences.