Read the Fine Print

A down-on-his luck writer wins a 100 million lottery and fulfills his life-long-dream. He buys a British title, Lordship Viscount St. Austell-in-the-Moor Biggleswade-Brixham and the castle that comes with this title for nearly 80 million. Unfortunately, he failed to read the fine print; “the new owner cannot inhabit the castle for 50 years, or until the last of the retired clowns currently inhabiting the castle are no more.” When informed of this clause, our down-on-his-luck writer becomes apoplectic and begings to suffer chest pains. He is taken to the ED where a diagnosis is made that indeed, he has an occluded coronary artery. Heart catheterization reveals only the posterior interventricular artery needs a stent and one is deployed. Which of the indicated arteries was first entered by the heart catheter to deliver the stent?

The posterior interventricular artery is a continuation of which artery?