Monitoring of Daily Body Weight and Intrathoracic Impedance in Heart Failure Patients With a High Risk of Volume Overload Decompensation

BACKGROUND: Decompensation is frequent in heart failure (HF) patients and predicts poor prognosis. HYPOTHESIS: Volume-overload events in HF patients are preceded by changes in intrathoracic impedance (Z) and body weight (BW); monitoring these parameters may be useful to predict decompensation. METHODS: Forty-three HF patients (LVEF 25% ± 12%) with a recent HF event and an implantable cardioverter-defibrillator providing daily Z were equipped with telemonitoring scales submitting daily BW. Changes in BW and Z 30 days prior to major (HF hospitalization) and minor (ambulatory adjustment of diuretics) were analyzed. RESULTS: During median of 427 days follow-up 25 major and 41 minor events occurred. Z decreased by -4.8 (95% confidence interval [CI]: CI -6.7 to -3.0) and -4.3 (95% CI: -5.5 to -3.2) within 30 days prior to major and minor events respectively (P < 0.001). BW increased before major events by 2.3 kg (95% CI: 1.0 to 3.5, P < 0.01) and minor events 1 kg (95% CI: 0.5 to 1.4, P < 0.001). Sensitivity of Z for major/minor HF events was 83.3% (95% CI: 71.7 to 91.0) and for BW 43.9% (95% CI: 31.9 to 56.7). The unexplained detection rate per patient-year was 1.6 (interquartile range [IQR], 0-3.1) for Z and 4.8 (IQR 1.6-11.1) for BW. Combined Z and BW sensitivity was 42.4% (95% CI: 30.6 to 55.2) and unexplained detection rate was 0.8 (IQR, 0-1.5) per patient-year. CONCLUSIONS: Decompensation is marked by a decrease in Z and increase in BW the preceding 30 days. Monitoring of Z predicts HF decompensations with better sensitivity and lower unexplained detection rate than BW.