Intrathoracic impedance and pulmonary wedge pressure for the detection of heart failure deterioration

The aims of this analysis were to assess the agreement between implantable defibrillator (ICD)-measured intrathoracic impedance and pulmonary capillary wedge pressure (PCWP) collected during long-term follow-up, as well as to evaluate whether PCWP measures may improve the performance of the impedance detection algorithm in predicting heart failure (HF) worsening. We studied 23 HF patients implanted with an ICD capable of intrathoracic impedance measurement and alerting for fluid accumulation diagnosis. At regular follow-up and at visits for HF decompensation or device alert, clinical status was assessed and PCWP was non-invasively estimated with a validated echo-Doppler method. During 23 +/- 11 months, 45 paired assessments of impedance and PCWP were performed. The Kappa analysis revealed good agreement between impedance and PCWP (k = 0.701, SE 0.113, P < 0.001). Moreover, PCWP estimations and the paired values of the impedance fluid index resulted significantly correlated (r = 0.677, P < 0.001). The impedance-alert detected clinical HF deterioration with 92% sensitivity and 69% positive predictive value. The combined finding of decreased impedance and increased PCWP resulted in enhanced positive predictive value (92%) and no change in sensitivity (92%). These data confirm the inverse correlation between impedance and PCWP at long-term follow-up and suggest the potential clinical value of a combined impedance and pressure assessment for the improved detection of HF deterioration.