Association between changes in the intrathoracic impedance and ventricular arrhythmias in patients with heart failure.

Background Ventricular arrhythmias (VAs) are independently related to mortality risk in patients with heart failure (HF). The wide availability of implantable cardioverter defibrillators and cardiac resynchronization therapy devices now offers an opportunity to clinically correlate the two disease processes. We hypothesized that there is an association between changes in the intrathoracic impedance and episodes of VA. Methods Nonconcurrent prospective study of adults (age >20 years) with known HF with reduced ejection fraction (<35%). The OptiVol threshold was categorized as follows: 0-30 omega-days, 31-60 omega-days, 61-90 omega-days, 91-120 omega-days, and >120 omega-days. Patients with OptiVol values at 0-30 omega-days were used as the reference group. Receiver operating characteristic analysis was used to estimate the sensitivity and specificity at each threshold. Results Of the 87 eligible patients, 65.5% were males. The mean age of the sample was 73.3 years (+/- 12.7). Compared to patients in the 0-30 omega-days category, those in the 31-60, 61-90, 91-120, and >120 omega-days groups had, on average, 1.48, 1.64, 2.24, and 1.6 more VAs, respectively (P = 0.002, 0.009, 0.010 and 0.009, respectively). The sensitivity and specificity of each threshold were as follows: 82.6% and 61.7% at 31-60 omega-days, 43.5% and 78.3% at 61-90 omega-days, 30.4% and 85.0% at 91-120 omega-days, and 21.7% and 88.3% at >121 omega-days. Conclusion Our study found a significant positive relationship between changes in intrathoracic impedance and episodes of VAs in patients with HF.