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QUARTERLY FOCUS ISSUE: HEART RHYTHM DISORDERS: CLINICAL RESEARCH

Transient Local Injury Current in Right Ventricular Electrogram After Implantable Cardioverter-Defibrillator Shock Predicts Heart Failure Progression

Larisa G. Tereshchenko, MD, PhD^_*,,_*, Mitchell N. Faddis, MD, PhD, Barry J. Fetics, MS^_*, Karl E. Zelik, MS^,, Igor R. Efimov, PhD and Ronald D. Berger, MD, PhD^_*

^_* Division of Cardiology, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland
Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri
Biomedical Engineering Department, Washington University in St. Louis, St. Louis, Missouri
University of Michigan, Ann Arbor, Michigan

Manuscript received February 4, 2009; revised manuscript received June 1, 2009, accepted June 11, 2009.

^_* Reprint requests and correspondence: Dr. Larisa G. Tereshchenko, Carnegie 592, 600 North Wolfe Street, Baltimore, Maryland 21287 (Email: lteresh1{at}jhmi.edu).

Objectives: This study aimed to identify an early marker of functional impairment after an implantable cardioverter-defibrillator (ICD) shock as a predictor of heart failure progression.

Background: The ICD population has substantial risk of death due to progressive pump failure.

Methods: Near-field (NF) bipolar right ventricular (RV) electrograms (EGMs) during induced ventricular fibrillation (VF) and 10 s after rescue ICD shock were analyzed in 310 patients (mean age 59 ± 14.5 years, 219 men [71%]) with structural heart disease, New York Heart Association functional class I to III, and implanted with a single- or dual-chamber Medtronic (Minneapolis, Minnesota) ICD for primary (245 patients, 79%) or secondary prevention of sudden cardiac arrest. A local injury current (LIC) on NF RV EGM was defined as a deviation of EGM potential 1 mV or 15% of the preceding R-wave peak-to-peak amplitude.

Results: During mean follow-up of 29.3 ± 15.0 months, the combined end point of death or hospitalization due to congestive heart failure (CHF) exacerbation was documented in 40 patients (12.9%, or 5.3% per person-year of follow-up). LIC was observed in 106 patients. In multivariate risk analysis, after adjustment for baseline prognostic factors (ejection fraction, history of atrial fibrillation, diabetes mellitus) and appropriate ICD shocks during follow-up, patients with observed LIC after induced VF rescue ICD shock at ICD implantation were more likely to die or to be hospitalized (hazard ratio: 2.69; 95% confidence interval: 1.41 to 5.14; p = 0.003).

Conclusions: Transient LIC on bipolar NF RV EGM after induced VF rescue ICD shock is associated with increased risk of CHF progression, future hospitalizations due to CHF exacerbation, and subsequent heart failure death.

Key Words: congestive heart failure • implantable cardioverter-defibrillator • ventricular tachyarrhythmia

Abbreviations and Acronyms   CHF = congestive heart failure   CI = confidence interval   DFT = defibrillation threshold testing   EGM = electrogram   HR = hazard ratio   ICD = implantable cardioverter-defibrillator   LIC = local injury current   LVEF = left ventricular ejection fraction   NF = near field   NYHA = New York Heart Association   RV = right ventricle/ventricular   SCA = sudden cardiac arrest   VF = ventricular fibrillation   VT = ventricular tachycardia

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