ASA January 2006 Newsletter

any anesthesiologists, surgeons, and cardiologists wrongly believe that all implantable cardioverter-defibrillators (ICDs) work, although most devices actually perform as designed and programmed. Most physicians also believe that a magnet will always suspend tachy therapy (such as shock). In fact misinformation about cardiac generator issues gets published all too frequently,¹ and these articles often generate comments submitted after publication, suggesting that the review process is lacking as well.² This area is ripe for patient injury, since many cardiac events get misinterpreted in patients with devices.^3-6 At least part of the problem is the lack of training, especially among cardiologists.⁷

In reality, most ICDs will suspend shock therapies upon magnet placement. Some ICDs can be programmed to ignore magnet placement (St. Jude Medical, Syl Mar, California; Guidant Medical, Indianapolis, Indiana; Angeion Corporation, St. Paul, Minnesota). When a magnet mode is present and enabled, often there is no good way to confirm appropriate magnet placement, since only ICDs from Guidant provide unambiguous feedback of correct magnet placement and, therefore, suspension of tachy therapies. It is interesting to note that some pacemakers also can be programmed to ignore magnet placement, yet many physicians wrongly believe that all pacemakers convert to some continuous, asynchronous pacing behavior with magnet placement.²

The notices in early 2005 by both Medtronic⁸ and Guidant^9-11 regarding premature battery failure in some defibrillators should serve as a wake-up call to insist on a preoperative evaluation of any device in any patient having an elective surgery. Even more alarming, Guidant issued a notice regarding malfunction of the magnetic reed switch in a number of their ICDs used in patients with severe cardiomyopathies, and Guidant recommends that magnet function be permanently disabled by programming in these ICDs.¹² Also Medtronic announced recently a problem with some Sigma pacemakers.¹³ And, unknown to most practitioners, some ICD leads “chatter,” creating electrical noise on the ventricular channel that can lead to inappropriate shock therapy without warning, especially in the setting of mild tachycardia (heart rates 90-100 bpm).

Following the course of action recommended in the ASA “Practice Advisory for Perioperative Management of Patients With Cardiac Rhythm Management Devices” <www.ASAhq.org/publicationsAndServices/CRMDAdvisory.pdf> approved by the ASA House of Delegates in October 2004 and published in the journal Anesthesiology,¹⁴ should prevent any untoward events that might arise, since the advisory recommends comprehensive generator evaluation both preoperatively and postoperatively. Although some authors and societies might consider this strategy unnecessary,¹⁵ it certainly provides the highest level of safety for our patients.

References:
1. Stone KR, McPherson CA. Assessment and management of patients with pacemakers and implantable cardioverter defibrillators. Crit Care Med. 2004; 32(4) (Suppl):S155-S165.
2. Rozner MA. Pacemakers and implantable cardioverter defibrillators. Crit Care Med. 2004; 32(8):1809-1812.
3. Rozner MA, Nishman RJ. Pacemaker-driven tachycardia revisited. Anesth Analg. 1999; 88(4):965.
4. Rozner MA, Nishman RJ. Electrocautery-induced pacemaker tachycardia: Why does this error continue? Anesthesiology. 2002; 96(3):773-774.
5. Rozner MA. Pacemaker and electrocardiographic monitor psuedomalfunction during extracardiac radiofrequency ablation. Anesthesiology. 2005; 102(1):239.
6. Southorn PA, Kamath GS, Vasdev GM, Hayes DL. Monitoring equipment induced tachycardia in patients with minute ventilation rate-responsive pacemakers. Br J Anaesth. 2000; 84(4):508-509.
7. Rozner MA. Pacemaker misinformation in the perioperative period: programming around the problem. Anesth Analg. 2004; 99(6):1582-1584.
8. ICD recall. Available at <www.medtronicinfo.com/overview.asp>. Published February 10, 2005. Accessed on December 8, 2005.
9. Important medical device safety information and corrective action (Insignia, Nexus). Available at <www.guidant.com/physician_communications/insignia-nexus.pdf>. Published September 22, 2005. Accessed on December 8, 2005.
10. Urgent medical device safety information and corrective action (Contak Renewal failure). Available at <www.guidant.com/physician_communications/RENEWAL_ RENEWAL2.pdf>. Published June 23, 2005. Accessed on December 8, 2005.
11. Urgent medical device safety information and corrective action (Prizm failure). Available at <www.guidant.com/physician_communications/PRIZM2_DR.pdf>. Published June 23, 2005. Accessed on December 8, 2005.
12. Urgent medical device safety information and corrective action (magnet issue). Available at <www.guidant.com/physician_communications/RENEWAL3_RENEWAL4.pdf>. Published on June 23, 2005. Accessed on December 8, 2005.
13. Important Patient Management Information. Available at <www.medtronic.com/crmLetter.html>. Accessed on December 8, 2005.
14. Practice advisory for the perioperative management of patients with cardiac rhythm management devices: pacemakers and implantable cardioverter-defibrillators: A report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients With Cardiac Rhythm Management Devices. Anesthesiology. 2005; 103(1):186-198.
15. Stevenson WG, Chaitman BR, Ellenbogen KA, et al. Subcommittee on Electrocardiography and Arrhythmias of the American Heart Association Council on Clinical Cardiology in Collaboration With the Heart Rhythm Society. Clinical assessment and management of patients with implanted cardioverter-defibrillators presenting to nonelectrophysiologists. Circulation. 2004; 110(25):3866-3869.

Marc A. Rozner, Ph.D., M.D., is Associate Professor of Anesthesiology and Cardiology, University of Texas M.D. Anderson Cancer Center and Adjunct Assistant Professor of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston.

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