Averted Catastrophic Transseptal Puncture: Percutaneous Transseptal Mitral Commissurotomy in a Patient With Undiagnosed Azygous Continuation of the Inferior Vena Cava

A case is presented of a patient requiring percutaneous mitral balloon commissurotomy. During positioning of the transseptal needle, an unusual needle position on the lateral projection prompted the physician to abandon the puncture and do an angiogram of the inferior vena cava. This revealed an azygous vein continuation. The valve was treated at a later date under general anesthesia with transesophageal echo guidance. This case illustrates how reliance on the posterior-anterior projection to find the optimal point for transseptal puncture can be very misleading and how crucial the lateral projection is.