Role of Lung Impedance Monitoring in the Outpatient Clinic for Predicting and Preventing of Hospitalizations Patients with Chronic Heart Failure

Abstract

Implantable intra-thoracic impedance device has shown that lung fluid accumulation in patients with decompensated chronic heart failure (CHF) begins several days before admission, but predicts hospitalizations with only 50-76% accuracy. We evaluated the ability of the new a non-invasive method for lung impedance monitoring to predict decompensation in CHF patients and to trigger early therapy in order to prevent hospitalizations. Lung impedance (LI) was measured by device based on transverse distribution of electromagnetic energy through the chest. Changes in the clinical status of patients, LI and NT-proBNP levels were concurrently recorded at each outpatient heart failure clinic visit (20±18 days). 150 CHF patients (72±10 years) at NYHA II/III/IV (60/60/30) were followed for 31±14 months in an outpatient clinic. Patients were treated with diuretics, beta blockers and ACE/ARB/aldosterone. An LI decrease>15% from normal baseline was used to initiate early preventive therapy since we have shown previously that clinical decompensation occurred at this level of LI decrease. 75 of 150 patients were treated by clinical evaluation (Group1) and 75 according to LI (Group 2). LVEF and NT-proBNP in groups 1 and 2 were 23±7%, 5820±2434 pg/ml, and 23±6% and 5868±2532 pg/ml, respectively (p=NS). 140 episodes of LI decrease>15% occurred in group 1 with treatment administered according to clinical signs only. These LI decrease episodes included 124 hospitalizations and 35 deaths. Positive predictive value for hospitalization at level of LI decrease>15% was 89%. In group 2, 149 episodes of LI decrease>15% were recorded. Treatment was immediately intensified. In 124 cases LI increased as the result of treatment intensification and only 25 hospitalizations were required (p<0.01) and 14 patients died (p<0.01). LI decrease at admission in group 2 (28±5.3%) was similar to that in group 1 (27±5.6%). Time elapsed between LI decrease > 15% and hospitalization in both groups was 16±6 days. Non invasive lung impedance monitoring of CHF patients in an outpatient clinic allows predict decompensation in 89%.