Derivation of baseline lung impedance in chronic heart failure patients: use for monitoring pulmonary congestion and predicting admissions for decompensation.

The instantaneous lung impedance (ILI) is one of the methods to assess pulmonary congestion or edema (PCE) in chronic heart failure (CHF) patients. Due to usually existing PCE in CHF patients when evaluated, baseline lung impedance (BLI) is unknown. Therefore, the relation of ILI to BLI is unknown. Our aim was to evaluate methods to calculate and appraise BLI or its derivative as reflecting the clinical status of CHF patients. ILI and New York Heart Association (NYHA) class were assessed in 222 patients (67 ± 11 years, LVEF <35 %) during 32 months of frequent outpatient clinic visits. ILI, measured in 120 asymptomatic patients at NYHA class I, with no congestion on the chest X-ray and a low-normal 6-min walk, was defined as BLI. Using measured BLI and ILI values in these patients, formulas for BLI calculation were derived based on logistic regression analysis or on the disparity between BLI and ILI values at different NYHA stages. Both models were equally reliable with <3 % difference between measured and calculated BLI (p = NS). ΔLIR = (ILI/BLI - 1) × 100 % reflected the degree of PCE, or deviation from baseline, correlated with NYHA class (r = -0.9, p < 0.001) and could serve for monitoring. Of study patients, 123 were re-hospitalized for PCE during follow up. Their ΔLIR decreased gradually from -21.7 ± 8.2 % 4 weeks pre-admission to -37.8 ± 9.3 % on admission (p < 0.001). Patients improved during hospital stay (NYHA 3.7 ± 0.5 to 2.9 ± 0.8, p < 0.0001) with ΔLIR increasing to -29.1 ± 12.0 % (p < 0.001). ΔLIR based on calculated BLI correlated with the clinical status of CHF patients and allowed the prediction of hospitalizations for PCE.

Usefulness of lung impedance-guided pre-emptive therapy to prevent pulmonary edema during ST-elevation myocardial infarction and to improve long-term outcomes.

Patients sustaining an ST-segment elevation myocardial infarction (STEMI) frequently develop pulmonary congestion or pulmonary edema (PED). We previously showed that lung impedance (LI) threshold decrease of 12% to 14% from baseline during admission for STEMI marks the onset of the transition zone from interstitial to alveolar edema and predicts evolution to PED with 98% probability. The aim of this study was to prove that pre-emptive LI-guided treatment may prevent PED and improve clinical outcomes. Five hundred sixty patients with STEMI and no signs of heart failure underwent LI monitoring for 84 ± 36 hours. Maximal LI decrease throughout monitoring did not exceed 12% in 347 patients who did not develop PED (group 1). In 213 patients LI reached the threshold level and, although still asymptomatic (Killip class I), these patients were then randomized to conventional (group 2, n = 142) or LI-guided (group 3, n = 71) pre-emptive therapy. In group 3, treatment was initiated at randomization (LI = -13.8 ± 0.6%). In contrast, conventionally treated patients (group 2) were treated only at onset of dyspnea occurring 4.1 ± 3.1 hours after randomization (LI = -25.8 ± 4.3%, p <0.001). All patients in group 2 but only 8 patients in group 3 (11%) developed Killip class II to IV PED (p <0.001). Unadjusted hospital mortality, length of stay, 1-year readmission rate, 6-year mortality, and new-onset heart failure occurred less in group 3 (p <0.001). Multivariate analysis adjusted for age, left ventricular ejection fraction, risk factors, peak creatine kinase, and admission creatinine and hemoglobin levels showed improved clinical outcome in group 3 (p <0.001). In conclusion, LI-guided pre-emptive therapy in patients with STEMI decreases the incidence of in-hospital PED and results in better short- and long-term outcomes.

A novel radiological score to assess lung fluid content during evolving acute heart failure in the course of acute myocardial infarction.

BACKGROUND: Monitoring of lung fluid content (LFC) in order to predict acute heart failure (AHF) during acute myocardial infarction (AMI) is an unmet challenge. AIM: To evaluate in AMI patients the ability of proposed radiological score (RS), which is the sum of selected radiological signs of congestion, to reflect correctly LFC, as assessed with repeat physical examinations and lung impedance (LI) measurements. METHODS: Chest X-rays were taken at baseline, when rales were detected, whenever indicated, and at conclusion of monitoring. RS grading for LFC assessment was: RS = 0-1 for normal X-ray, RS = 2-4 for interstitial congestion, and RS values of 5-6, 7-8 and 9-10 signified mild, moderate and severe alveolar edema, respectively. RESULTS: 624 AMI patients without AHF at baseline were monitored (94 ± 42 h). 476 patients (76%) with baseline RS of 0.3 ± 0.5 did not develop AHF. Overt AHF developed in 148 patients (24%) during monitoring; baseline RS (0.6 ± 0.8) reached 5.4 ± 0.7, 7.0 ± 0.8, and 9.8 ± 0.5 at the stages of mild, moderate, and severe alveolar edema, respectively. AHF resolved with treatment. RS decreased to 1.5 ± 1.3 (P < 0.01) and correlated with physical examination (r = 0.6, P < 0.01) and LI (r = -0.9, P < 0.01). CONCLUSION: RS correlated well with findings on physical examination during AHF and closely correlated with LI.