Intrathoracic impedance and ultrasound lung comets in heart failure deterioration monitoring.

PURPOSE

Echographic examination of the lung surface may reveal multiple ultrasound lung comets (ULCs) originating from water-thickened interlobular septa. These images were demonstrated to be useful for noninvasive assessment of interstitial pulmonary edema. Similarly, the correlation between implantable defibrillator-measured intrathoracic impedance and pulmonary capillary wedge pressure (PCWP) was demonstrated in heart failure (HF) patients. The aims of this analysis were to assess the agreement between defibrillator-detected impedance decrease and the presence of ULCs, as well as to compare the performance of the impedance-detection algorithm and the ULCs assessment in predicting HF worsening.

METHODS AND RESULTS

We studied 23 HF patients implanted with a defibrillator 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, chest ultrasound was performed, and PCWP was noninvasively estimated with Doppler echocardiography. During 23 ± 11 months of follow-up, 45 paired assessments of defibrillator-measured intrathoracic impedance and ULCs were performed. The number of ULCs resulted significantly correlated to the paired PCWP estimations (r = 0.917, P < 0.001) and to the impedance fluid index (r = 0.669, P < 0.001). During follow-up, 12 episodes of HF decompensation were reported in 12 patients. The impedance alert detected clinical HF deterioration with 92% sensitivity and 69% positive predictive value. The presence of ≥5 ULCs showed 83% sensitivity and 91% positive predictive value.

CONCLUSIONS

These data demonstrate the correlation between intrathoracic impedance and the number of ULCs at chest ultrasound, and a good agreement between the defibrillator warning for fluid index and the detection of multiple ULCs.