Advertisement

The Implantable Atrial Defibrillator: Are All the Problems Solved

  • S. Lévy

Abstract

Atrial fibrillation (AF) is an extremely common arrhythmia seen in clinical practice, as shown by a number of epidemiologic studies. A significant number of patients either have recurrent attacks of atrial fibrillation despite pharmacological therapy, or are controlled, but complain of intolerable side effects. The atrial defibrillator (AID), a device capable of detecting and automatically terminating AF, may be an interesting non-pharmacological therapy of atrial fibrillation. Two devices are currently available for clinical evaluation: The Metrix system (In Control Redmond, USA) which is a stand-alone defibrillator, and the Medtronic 2030 which is a double-chamber defibrillator under evaluation solely in patients in whom a ventricular defibrillator is indicated, and who have paroxysmal atrial fibrillation. This presentation will focus on the Metrix system aimed at the trat-ment of patients whose major clinical problem is atrial fibrillation. This type of system has to deal with four issues: (1) the feasibility of atrial defibrillation, (2) the possible shock-related discomfort, (3) the safety of the device, and (4) the proper identification of patients who might benefit from the device. Several studies have shown that atrial defibrillation using low-energy shocks between two intracardiac catheters, in the coronary sinus and in the right atrium is feasible in patients with persistent spontaneous atrial fibrillation. As the minimum energy requirement in order to successfully terminate atrial fibrillation in 75% of patients averages 200-300 V (2–3 J), the conversion voltage needs to be above these values in order to have a satisfactory safety margin. Termination of atrial fibrillation with energy levels of less than 1 joule was found to be associated with little, if any discomfort. A good correlation was also found in our study between the level of discomfort and increasing voltage. The difference was statistically significant (p < 0.02) between 140 V and 220 V shocks and 220 V and 300 V shocks (p < 0.01). A marked inter-individual variation was noted. Therefore, this aspect should be tested before indicating the device in a given patient. Both in the XAD study and the Metrix study with the physician-activated device in more than 50 patients and more than 3000 shocks, no ventricular proarrhythmia was observed with synchronized shock. As shocks delivered following short (below 300 ms) RR intervals were associated with a low but definite risk of ventricular fibrillation, the shocks were delivered after an RR interval of 500 ms or longer.

Keywords

Atrial Fibrillation Paroxysmal Atrial Fibrillation Chronic Atrial Fibrillation Intolerable Side Effect Minimum Energy Requirement 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Suggested Readings

  1. Kannel WB, Abbott RD, Savage DD (1982) Epidemiologic features of chronic atrial fibrillation: The Framingham study. N Engl J Med 306: 1018-1022Google Scholar
  2. Bialy D, Lehmann MH, Schumacher DM et al (1992) Hospitalization or arrhythmias in the United States: Importance of atrial fibrillation. J Am Coll Cardiol 19: 41AGoogle Scholar
  3. Pritchett ELC (1992) Management of atrial fibrillation. N Engl J Med 326: 1264 - 1271PubMedCrossRefGoogle Scholar
  4. Lévy S, Camm AJ (1993) An implantable atrial defibrillator: An impossible dream? Circulation 87: 1769 - 1772PubMedCrossRefGoogle Scholar
  5. Cooper RAS, Alferness CA, Smith WM et al (1993) Internal cardioversion of atrial fibrillation in sheep. Circulation 87: 1673 - 1686PubMedCrossRefGoogle Scholar
  6. Murgatroyd F, Slade AKB, Sopher M, Rowland E, Ward DE, Camm J (1995) Efficacy and tolerability of transvenous low energy cardioversion of paroxysmal atrial fibrillation in humans. J Am Coll Cardiol 25: 1347 - 1353PubMedCrossRefGoogle Scholar
  7. Keane D, Sulke N, Cooke R et al (1993) Endocardial cardioversion of atrial flutter and fibrillation. PACE 16: 928Google Scholar
  8. Johnson E, Smith W, Yarger M et al (1994) Clinical predictors of low energy defibrillation thresholds in patients undergoing internal cardioversion of atrial fibrillation. PACE 17: 742 (abstr)Google Scholar
  9. Lévy S, Ricard Ph, Pak Law C, Lok NS, Camm JA, Murgatroyd F, Jordaens LJ, Kappenberger LJ, Brugada P, Ripley KL (1997) Multicenter low energy transvenous atrial defibrillation ( XAD) trial results in different subject of atrial fibrillation. JACC 29: 750-755Google Scholar
  10. Lévy S, Ricard Ph (1997) Low energy cardioversion of spontaneous atrial fibrillation: Immediate and long-term results. Circulation (in press)Google Scholar
  11. Alt E, Schmitt C, Ammer R, Coenen M et al (1994) Initial experience with intracardiac atrial defibrillation in patients with chronic atrial fibrillation. PACE 17: 1067 - 1078PubMedCrossRefGoogle Scholar
  12. Lévy S, Novella P, Ricard Ph et al (1995) Paroxysmal atrial fibrillation: A need for classification. J Cardiovasc Electrophysiol 6: 69-74Google Scholar
  13. Ayers GM, Alferness CA, Ilina M et al (1994) Ventricular proarrhythmic effects of ventricular cycle length and shock strength in a sheep model of transvenous atrial defibrillation. Circulation 89: 413 - 422PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Italia 1998

Authors and Affiliations

  • S. Lévy
    • 1
  1. 1.University of Marseille, School of Medicine, Hôpital NordMarseilleFrance

Personalised recommendations