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

Aims: 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.

Methods And Results: 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%).

Conclusion: 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.