During a percutaneous coronary intervention (PCI) to restore perfusion in a coronary artery, the procedure typically involves placing a stent to keep the artery open after balloon angioplasty. In this case, since the options are presented, the most likely occurrence during PCI for Helen would be drug-eluting stent placement.
Drug-eluting stents are commonly used during PCI as they help prevent the recurrence of blockages by releasing medication that inhibits cell growth in the artery, thereby reducing the risk of restenosis.
The other options listed (Thallium stress test, heart valve replacement, aortic dissection) are not standard components of a PCI procedure.