CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Peter Sick, MD*
* Krankenhaus Barmherzige Brüder Regensburg, Medizinische Klinik III/Kardiologie, Prüfeningerstrasse 86, 93049 Regensburg, Germany (Email: peter.sick{at}barmherzige-regensburg.de).
Although we are pleased that Drs. Stöllberger and Finsterer read our article with interest, their letter titled "An Out-of-Date-Procedure" seems to be part of their series of editorials against left atrial appendage (LAA) occlusion, made particularly odd in this instance by the claim that use of these devices will contribute to the obesity epidemic and global warming. We are also puzzled by the characterization of this technology as "out of date," considering that it is currently undergoing its first randomized prospective trial.
Drs. Stöllberger and Finsterer state that they are prompted "to challenge the authors’ conclusion that LAA occlusion with the WATCHMAN system is safe and effective." We are unable to find any allusion to "safe and effective" in our report (1). Claims for efficacy are not, as they might not be aware, designed into pilot trials. Indeed we were careful to state that the study was not powered to address efficacy and that the data are preliminary, suggesting safety and feasibility only. We hope safety and efficacy will be shown by the randomized PROTECT-AF pivotal trial, with currently over 400 patients enrolled (2).
With regard to the prevalence of thrombus in the LAA in un-anticoagulated patients, the rate of 2.5% to which the letter’s authors allude comes from their data (3) and varies from the rest of the published data, reporting left atrial thrombus in up to 25% of un-anticoagulated atrial fibrillation (AF) patients (4–6). Their concerns relating to possible significance of the proximity of the circumflex coronary artery, possible undersizing of devices, potential difficulties with device fixation, and leakage "of a primarily completely closed LAA," although important to consider, are based only on speculation, in some cases refer to the surgical rather than percutaneous experience, and have as yet no evidence base for support. Drs. Stöllberger and Finsterer do reference their case report of a patient with device embolization who was not part of this trial. We are puzzled by their pre-publication of that particular case despite its being part of an ongoing study in which they have no involvement.
Our study was too small to address a number of their queries that will be part of the analysis of the large pivotal study under way. As the authors must be aware, pilot trials generally exclude the highest-risk patients, in this case so as not to withhold anticoagulation until feasibility is shown. Regardless, the patient population in our pilot study is from a vast pool of AF patients, the majority of whom worldwide are not anticoagulated, despite the well-reported 6:1 ratio of embolic events in the absence of anticoagulation (7).
We are pleased to have in common with Drs. Stöllberger and Finsterer our considerable enthusiasm for eliminating the obesity and global warming epidemics, but their implicating LAA-occlusion in these "epidemia" is, like their letter, a bit extreme. Far from needing to be "strongly re-considered," the device is just now being considered in the first place with the crucible of a carefully designed, conducted, and monitored randomized trial. If the WATCHMAN is in fact safe and effective, it has the potential of contributing uniquely to the welfare of AF patients. We look forward to analyzing those results based on the scientific method.
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References
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1. Sick PB, Schuler G, Hauptmann KE, et al. Initial worldwide experience with the WATCHMAN left atrial appendage system for stroke prevention in atrial fibrillation J Am Coll Cardiol 2007;49:1490-1495.[Abstract/Free Full Text]2. Fountain RB, Holmes DR, Chandrasekaran K, et al. The PROTECT AF (WATCHMAN Left Atrial Appendage System for Embolic PROTECTion in Patients with Atrial Fibrillation) trial Am Heart J 2006;151:956-961.[CrossRef][Web of Science][Medline] 3. Stollberger C, Chnupa P, Kronik G, et al. Transesophageal echocardiography to assess embolic risk in patients with atrial fibrillation Ann Intern Med 1998;128:630-638.[Abstract/Free Full Text] 4. Dawn B, Varma J, Singh P, et al. Cardiovascular death in patients with atrial fibrillation is better predicted by left atrial thrombus and spontaneous echocardiographic contrast as compared with clinical parameters J Am Soc Echocardiogr 2005;18:199-205.[CrossRef][Web of Science][Medline] 5. Stoddard MF, Singh P, Dawn B, et al. Left atrial thrombus predicts transient ischemic attack in patients with atrial fibrillation Am Heart J 2003;145:676-682.[CrossRef][Web of Science][Medline] 6. Blackshear JL, Odell JA. Appendage obliteration to reduce stroke in cardiac surgical patients with atrial fibrillation Ann Thorac Surg 1996;61:755-759.[Abstract/Free Full Text] 7. Caro JJ, Groome PA, Flegel KM. Atrial fibrillation and anticoagulation: from randomised trials to practice Lancet 1993;341:1381-1384.[CrossRef][Web of Science][Medline]
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