Incidence of Newly Detected Atrial Arrhythmias Through Implantable Devices in Patients With a History of Thromboembolic Events
To the Editor:
I read the article by Ziegler et al,1 and their results are an important addition to the literature on the high detection rate of paroxysmal atrial fibrillation (AF) in patients with cryptogenic stroke. I have some concern, however, about some of the definitions the authors used, particularly on the duration of AF. The authors cite a report from the Heart Rhythm Society (HRS)2 about the definition of AF being >30 seconds as a justification for longer cardiac monitoring. They comment on this duration because the study by Tayal et al3 reported AF of <30 seconds using an external monitor. However, the HRS document directly refers to a consensus statement by the American College of Cardiology, which the authors could have referenced, and which also includes the following statement: “Episodes of AF briefer than 30 s may be important in certain clinical situations involving symptomatic patients, preexcitation or in assessing the effectiveness of therapeutic interventions.”4 I would argue that a patient with a prior embolic stroke would be considered symptomatic. Given the superiority of warfarin over aspirin for AF, and the equivalent safety and effectiveness of warfarin and aspirin in the Warfarin-Aspirin Recurrent Stroke Study (WARSS) trial for cryptogenic stroke,5 the <30-second episodes may be sufficient to change management in cryptogenic strokes. The authors then use a 5-minute justification of atrial fibrillation based on results from the MOde Selection Trial (MOST) study.6 However, a 5-minute cutoff was only used for high rate atrial arrhythmias and was not used for AF; it was not AF that was associated with the outcomes mentioned in the report by Ziegler. The authors go on to advocate for prolonged monitors that are placed subcutaneously, which are incidentally also made by Medtronic (funding source for the article and employer of several of the authors), although a trial is currently underway to evaluate the effectiveness of these devices. Further statements on the role of the funding source may have been helpful. The authors indicate that the rate of detection of AF increased to 36% using a shorter time interval, but it may have been useful to see the Kaplan-Meier curves for that time window. It could be that an externally placed device may be sufficient to detect clinically important AF within 30 days.
Ziegler PD, Glotzer TV, Daoud EG, Wyse DG, Singer DE, Ezekowitz MD, Koehler JL, Hilker CE. Incidence of Newly Detected Atrial Arrhythmias Via Implantable Devices in Patients With a History of Thromboembolic Events. Stroke. 2010; 41: 256–260.
Calkins H, Brugada J, Packer DL, Cappato R, Chen SA, Crijns HJ, Damiano RJ Jr, Davies DW, Haines DE, Haissaguerre M, Iesaka Y, Jackman W, Jais P, Kottkamp H, Kuck KH, Lindsay BD, Marchlinski FE, McCarthy PM, Mont JL, Morady F, Nademanee K, Natale A, Pappone C, Prystowsky E, Raviele A, Ruskin JN, Shemin RJ. HRS/EHRA/ECAS expert Consensus Statement on catheter and surgical ablation of atrial fibrillation: recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on catheter and surgical ablation of atrial fibrillation. Heart Rhythm. 2007; 4: 816–861.
Tayal AH, Tian M, Kelly KM, Jones SC, Wright DG, Singh D, Jarouse J, Brillman J, Murali S, Gupta R. Atrial fibrillation detected by mobile cardiac outpatient telemetry in cryptogenic TIA or stroke. Neurology. 2008; 71: 1696–1701.
European Heart Rhythm Association; Heart Rhythm Society; Fuster V, Rydén LE, Cannom DS, Crijns HJ, Curtis AB, Ellenbogen KA, Halperin JL, Le Heuzey JY, Kay GN, Lowe JE, Olsson SB, Prystowsky EN, Tamargo JL, Wann S, Smith SC Jr, Jacobs AK, Adams CD, Anderson JL, Antman EM, Hunt SA, Nishimura R, Ornato JP, Page RL, Riegel B, Priori SG, Blanc JJ, Budaj A, Camm AJ, Dean V, Deckers JW, Despres C, Dickstein K, Lekakis J, McGregor K, Metra M, Morais J, Osterspey A, Zamorano JL; American College of Cardiology; American Heart Association Task Force on Practice Guidelines; European Society of Cardiology Committee for Practice Guidelines; Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation). J Am Coll Cardiol. 2006; 48: 854–906.
Mohr JP, Thompson JL, Lazar RM, Levin B, Sacco RL, Furie KL, Kistler JP, Albers GW, Pettigrew LC, Adams HP Jr, Jackson CM, Pullicino P; Warfarin-Aspirin Recurrent Stroke Study Group. A comparison of warfarin and aspirin for the prevention of recurrent ischemic stroke. N Engl J Med. 2001; 345: 1444–1451.
Glotzer TV, Hellkamp AS, Zimmerman J, Sweeney MO, Yee R, Marinchak R, Cook J, Paraschos A, Love J, Radoslovich G, Lee KL, Lamas GA. Atrial high rate episodes detected by pacemaker diagnostics predict death and stroke: report of the Atrial Diagnostics Ancillary Study of the MOde Selection Trial (MOST). Circulation. 2003; 107: 1614–1619.