Late Thrombosis After Radiation: Sitting on a Time Bomb

Abstract

ive years after Condado et al 1 first treated human coronary arteries with brachytherapy, there is ongoing clinical investigation into its safety and efficacy in preventing restenosis.As with any novel technique, unexpected complications may dampen early high expectations and result in pessimism and skepticism.However, time, experience, and complete data analysis will determine the reality. See p 789Costa and coworkers 2 may be reacting prematurely by reporting a new phenomenon in interventional cardiology entitled "late, sudden thrombosis after PTCA plus radiotherapy."They report 6 (6.6%) of 91 patients who presented with late total occlusion/thrombosis at angiographic follow-up; these patients were enrolled into different radiation protocols using different ␤-emitters at different prescribed doses.Late total occlusion or late thrombosis is a valid concern, especially when associated with acute myocardial infarction (MI).However, can we really draw any conclusion from 6 heterogeneous case reports taken from a small cohort of patients in the absence of a control group?Is this announcement based on too few data, and is it premature?An editorial based on a Brief Rapid Communication mandates the editorialist to gather additional information, disclose his own insights, and provide the readers (the jury in this case) with as much information as possible. Definition and NomenclatureAcute thrombosis occurs during or early after intervention, and subacute thrombosis occurs within the subsequent 30 days.Both usually present with unstable symptoms and angiographic evidence of thrombus.However, the definition of late thrombosis may be problematic.It may not present with symptoms.It may be detected only when follow-up angiography shows a late total occlusion, which could also be the result of progressive intimal hyperplasia.Late total occlusion/thrombosis should be defined as any angiographically documented total occlusion Ͼ30 days after the proce-dure.For patients who have a patent treatment site at 6 months and subsequently develop a total occlusion, we propose the term "late late thrombosis."Based on these new definitions, the investigators presented 4 patients with late thrombosis and 2 with late late thrombosis.