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Original article
Safety threshold of R-wave amplitudes in patients with implantable cardioverter defibrillator
  1. J M Lillo-Castellano1,2,
  2. Manuel Marina-Breysse1,
  3. Alfonso Gómez-Gallanti3,
  4. J B Martínez-Ferrer4,
  5. Javier Alzueta5,
  6. Luisa Pérez-Álvarez6,
  7. Arcadi Alberola7,
  8. Ignacio Fernández-Lozano8,
  9. Anibal Rodríguez9,
  10. Rosa Porro10,
  11. Ignacio Anguera11,
  12. Adolfo Fontenla12,
  13. J J González-Ferrer13,
  14. Victoria Cañadas-Godoy13,
  15. Nicasio Pérez-Castellano13,
  16. Daniel Garófalo3,
  17. Óscar Salvador-Montañés3,
  18. Conrado J Calvo1,14,
  19. Jorge G Quintanilla1,13,
  20. Rafael Peinado3,
  21. Inmaculada Mora-Jiménez2,
  22. Julián Pérez-Villacastín13,
  23. J L Rojo-Álvarez2,
  24. David Filgueiras-Rama1,13
  1. 1Myocardial Pathophysiology Area, Fundación Centro Nacional de Investigaciones Cardiovasculares, Carlos III (CNIC), Madrid, Spain
  2. 2Department of Signal Theory and Communications, Telematics and Computing, Universidad Rey Juan Carlos (URJC), Madrid, Spain
  3. 3Department of Cardiology, Hospital Universitario La Paz, Madrid, Spain
  4. 4Department of Cardiology, Hospital Universitario de Araba, Vitoria, Spain
  5. 5Department of Cardiology, Hospital Universitario Virgen de la Victoria, Málaga, Spain
  6. 6Department of Cardiology, Hospital Universitario A Coruña, La Coruña, Spain
  7. 7Department of Cardiology, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain
  8. 8Department of Cardiology, Hospital Universitario Puerta de Hierro, Madrid, Spain
  9. 9Department of Cardiology, Hospital Universitario de Canarias, Santa Cruz de Tenerife, Spain
  10. 10Department of Cardiology, Hospital San Pedro de Alcántara, Cáceres, Spain
  11. 11Department of Cardiology, Hospital de Bellvitge, Barcelona, Spain
  12. 12Department of Cardiology, Hospital 12 de Octubre, Madrid, Spain
  13. 13Department of Cardiology, Hospital Clínico San Carlos, Madrid, Spain
  14. 14Department of Electrical Engineering, Universitat Politècnica de Valencia, Valencia, Spain
  1. Correspondence to Dr David Filgueiras-Rama, Fundación Centro Nacional de Investigaciones Cardiovasculares, (CNIC). Melchor Fernández Almagro, 3. Madrid, 28029, Spain; david.filgueiras{at}


Objective A safety threshold for baseline rhythm R-wave amplitudes during follow-up of implantable cardioverter defibrillators (ICD) has not been established. We aimed to analyse the amplitude distribution and undersensing rate during spontaneous episodes of ventricular fibrillation (VF), and define a safety amplitude threshold for baseline R-waves.

Methods Data were obtained from an observational multicentre registry conducted at 48 centres in Spain. Baseline R-wave amplitudes and VF events were prospectively registered by remote monitoring. Signal processing algorithms were used to compare amplitudes of baseline R-waves with VF R-waves. All undersensed R-waves after the blanking period (120 ms) were manually marked.

Results We studied 2507 patients from August 2011 to September 2014, which yielded 229 VF episodes (cycle length 189.6±29.1 ms) from 83 patients that were suitable for R-wave comparisons (follow-up 2.7±2.6 years). The majority (77.6%) of VF R-waves (n=13953) showed lower amplitudes than the reference baseline R-wave. The decrease in VF amplitude was progressively attenuated among subgroups of baseline R-wave amplitude (≥17; ≥12 to <17; ≥7 to <12; ≥2.2 to <7 mV) from the highest to the lowest: median deviations −51.2% to +22.4%, respectively (p=0.027). There were no significant differences in undersensing rates of VF R-waves among subgroups. Both the normalised histogram distribution and the undersensing risk function obtained from the ≥2.2 to <7 mV subgroup enabled the prediction that baseline R-wave amplitudes ≤2.5 mV (interquartile range: 2.3–2.8 mV) may lead to ≥25% of undersensed VF R-waves.

Conclusions Baseline R-wave amplitudes ≤2.5 mV during follow-up of patients with ICDs may lead to high risk of delayed detection of VF.

Trial registration number NCT01561144; results.

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