ICD Indications: What's New in 2003?

Andrew E. Epstein, MD

Disclosures

May 28, 2003

Editorial Collaboration

Medscape &

The 24th Annual Scientific Sessions of the North American Society of Pacing and Electrophysiology (NASPE) was held in Washington, DC, from May 14-17, 2003. In 2002, the ACC/AHA/NASPE committee established to revise guidelines for the implantation of antiarrhythmia devices updated the previously published (1998) version of the document. In addition to some minor wording changes, major new recommendations regarding implantable cardioverter-defibrillators (ICDs) were made, including:

  1. ICD implantation for spontaneous ventricular tachycardia not amenable to other treatments in patients with no structural heart disease (Class I indication).

  2. ICD implantation for patients at least 1 month post-MI and 3 months post coronary revascularization and a left ventricular ejection fraction ≤ 0.30 (the so-called MADIT II indication, Class IIa indication).

  3. ICD implantation for patients with syncope of unexplained origin or family history of unexplained sudden cardiac death in association with typical or atypical right bundle branch block and ST-segment elevations (Brugada syndrome, Class IIb indication).

  4. ICD implantation for patients with syncope and advanced structural heart disease in whom thorough invasive and noninvasive investigations have failed to define a cause (Class IIb indication).

MADIT II (Multicenter Automatic Defibrillator Implantation Trial II) Substudy Findings

The presentations at the NASPE Scientific Sessions refined and reinforced these guideline recommendations. One issue that has, in part, been responsible for the slow approval of prophylactic ICD reimbursement in patients with coronary artery disease and left ventricular ejection fractions ≤ 0.30 has been the difficulty in identifying subsets of this group who may derive special benefit.

Limitations of Electrophysiologic Studies

Dr. James P. Daubert (University of Rochester Medical Center, Rochester, New York) presented the electrophysiologic study results from patients in the MADIT II study,[1] with emphasis on their ability to predict subsequent ventricular tachycardia and fibrillation events.[2] Of 742 patients randomized to defibrillator therapy, 583 underwent electrophysiologic study. Ventricular arrhythmias were induced in 210 of these individuals (36%). The main findings of the study were that inducibility showed a trend to predict subsequent ICD therapy delivery, but only for patients with inducible ventricular tachycardia. Conversely, ventricular arrhythmia inducibility was inversely related to the occurrence of ventricular fibrillation. The implications of this study are that inducibility is not predictive of mortality and ICD use. Therefore, in patients post-MI with left ventricular ejection fractions ≤ 0.30, electrophysiologic study is not indicated to select those for prophylactic defibrillator implantation.

Further limitations of the clinical utility of electrophysiologic study were presented by Dr. Helmut U. Klein and colleagues (Otto-von-Guericke University, Magdeburg, Germany), who discussed the reproducibility of electrophysiologic study testing in a group of 56 patients enrolled in the MADIT II study from 2 centers.[3] Of these patients, 23% had an inducible ventricular arrhythmia at baseline. At a second electrophysiologic study, 27% of the inducible patients had become noninducible. Conversely, 18% of patients with an inducible arrhythmia had become noninducible at the second study. Similar reversals were seen at a third electrophysiologic study, when performed. Thus, neither inducibility nor noninducibility of ventricular tachycardia is a reliable marker for risk stratification, and further limits the clinical utility of electrophysiologic study testing.

Mechanisms of Death in MADIT II

Further insight into the MADIT II study findings was provided by Dr. Henry M. Greenberg (St. Luke's-Roosevelt Hospital, New York, NY), who presented the mechanisms of death in MADIT II.[4] He and his coauthors showed that the efficacy of the ICD in decreasing total mortality is primarily due to the reduction of sudden arrhythmic events. The data also suggested that, by preventing death from malignant arrhythmias, ICD use postpones death with a potential for increasing the frequency of congestive heart failure admission.

Dr. William N. Brodine (Research Medical Center, Kansas City, Missouri), showed that beta-blocker use was not associated with a significant reduction in the time to first appropriate defibrillator therapy in MADIT II, perhaps because background therapy with other drugs was so well tailored to patient care.[5]

Finally, Dr. David J. Wilber (Loyola University Medical Center, Maywood, Illinois) reported that the survival benefit of the ICD increases with time, indeed, up to 15 years following MI.[6] In short, all the MADIT II presentations reinforced the robustness of the data and durability of prophylactic ICD therapy in patients with similar characteristics to those of MADIT II patients.

Reliability of ICD Generators and Leads

In addition to the above, several important papers were presented regarding the other aspects of ICD therapy. Dr. Anzhen Qi, University of British Columbia, Vancouver, Canada, analyzed the long-term reliability of ICD generators and leads.[7] After 3 years following implantation, 14% of ICDs were explanted and replaced. Device recall was the most common reason for early replacement. The authors also found that generator reliability differs significantly between manufacturers and that reliability of the high voltage lead was 93% at 3-year follow-up.

Further information on the reliability of defibrillator leads was presented by Dr. Slawomir Weretka, University Hospital (Heidelberg, Germany), in a study of 450 patients.[8] They reported that one particular polyurethane lead had a 47% failure at 8 years. The authors went on to recommend that polyurethane leads be replaced at 4 years, and at every device replacement irrespective of intraoperative testing results. A member of the audience commented that this decision should be patient and lead specific.

Dr. Robert Hauser (Minneapolis Heart Institution Foundation, Minneapolis, Minnesota) reported from the Multicenter Registry that the mean time to ICD generator failure due to any cause was 3.9 +/- 1.3 years for 442 single-chamber devices, and 2.5 +/- 1.3 years for 53 dual-chamber devices.[9] The mean time to failure for 136 ICD leads was 4.5 +/- 2.7 years, including 5.7 +/- 2.5 years for 74 coaxial polyurethane leads and 3.0 +/- 2.3 years for 61 multilumen silicone leads. The authors concluded that lead failures occur regardless of design.

Biventricular Pacing/Defibrillator Systems

Regarding the implantation of biventricular pacing/defibrillator systems, from both US Food and Drug Administration (FDA) and ACC/AHA/NASPE guideline perspectives, biventricular pacing ICDs are appropriate for patients when both ICD and heart failure pacing indications are present. The durability of long-term benefit from biventricular pacing was substantiated by Dr. Michael Giudici (Genesis Heart Institute, Davenport, Iowa) and Dr. Bradley Knight (University of Chicago Hospitals, Chicago, Illinois).[10,11]

In Dr. Giudici's presentation, symptomatic improvement associated with cardiac resynchronization therapy in conjunction with an implantable defibrillator was sustained in the majority of responders through 30 months of follow-up. Dr. Knight reported that 3.4% of patients (15/443) were unable to have sustained therapy due to diaphragmatic or phrenic nerve stimulation, uncorrected loss of left ventricular capture, symptoms associated with the therapy, system explantation due to infection without replacement, and left ventricular conductor coil fracture. With this knowledge will come further improvement in this technology that will undoubtedly translate into improved patient care, quality of life, and outcome.

References
  1. Moss AJ, Zareba W, Hall WJ, et al, for the Multicenter Automatic Defibrillator Implantation Trial II Investigators. Prophylactic implantation on a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002;346:877-883.

  2. Daubert JP, Zareba W, Schuger C, et al. Does EPS inducibility in MADIT II patients predict subsequent VT and/or VF events? PACE. 2003;26(Pt II):960. Abstract 127.

  3. Reek S, Klein HU, Neumann T, et al. Reproducibility of electrophysiological testing in patients with remote myocardial infarction and severe left ventricular dysfunction: MADIT II substudy. PACE. 2003;26(Pt II):960. Abstract 128.

  4. Greenberg HM, Case RB, Brown MW, Carroll ER, Moss AJ, for the MADIT II Investigators. Mechanisms of mortality in the Multicenter Automatic Defibrillator Implantation Trial (MADIT II). PACE. 2003;26(Pt II):961. Abstract 129.

  5. Brodine WN, Tung RT, Lee JK, Lee B, Zareba W, Moss AJ. Beta blocker use & appropriate ICD therapy in the MADIT-II study. PACE. 2003;26(Pt II):961. Abstract 131.

  6. Wilber DJ, Zareba W, Hall WJ, Brown M, Moss AJ. Time-dependence of mortality risk and defibrillator benefit following myocardial infarction: lesions from the Multicenter Automatic Defibrillator Implantation Trial II. PACE. 2003;26(Pt II):961. Abstract 130.

  7. QI A, Kerr CR, Humphries KH, et al. Long-term reliability analysis of implantable cardioverter defibrillator generators and high voltage leads: frequency and causes of removal from service. PACE. 2003;26(Pt II):1014. Abstract 344.

  8. Weretka S, Becker R, Voss F, et al. Long-term performance of defibrillator leads: a study on 450 patients. PACE. 2003;26(Pt II):935. Abstract 25.

  9. Hauser RG, Gornick CC, Parsonnet V, et al. ICD system longevity and reliability: results from the multicenter registry. PACE. 2003;26(Pt II):1013. Abstract 338.

  10. Giudici MC, Boehmer J, Birgersdotter-Green U, Yong P. Symptomatic improvement with cardiac resynchronization therapy: how long will it last? PACE. 2003;26(Pt II):939. Abstract 43.

  11. Knight BP, Coman J, Faddis M, Bailin S, Yong P. Long-term retention of cardiac resynchronization therapy. PACE. 2003;26(Pt II):940. Abstract 48.

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