Long-Term Increase of Intrathoracic Impedance after Cardiac Resynchronization Therapy Is Associated with Left Ventricular Reverse Remodeling

Abstract

Backgrounds: Although acute decrease of intrathoracic impedance measured by cardiac resynchronization therapy (CRT) is effective to detect pulmonary congestion, it is unclear about the association with long-term change of intrathoracic impedance and left ventricular (LV) function in chronic heart failure (CHF) patients with CRT. Methods: Twenty six CHF patients who received CRT-defibrillator (CRT-D) were enrolled. LV dimensions, LV ejection fraction (LVEF) and B-type natriuretic peptide (BNP) were measured before and 6 months after CRT-D implantation. LV reverse remodeling was defined as >15% reduction in LV end-systolic volume after 6 months. In addition, intrathoracic impedance at 1 and 6 months after CRT-D implantation was investigated. The study subjects were divided into 2 groups: 18 patients with increased levels of intrathoracic impedance (Group-A) and 8 patients with decreased (Group-B). We compared LVEF, BNP levels and LV reverse remodeling between two groups. Results: In Group-A, BNP levels decreased and LVEF increased at 6 months after CRT-D implantation (P=0.01, each). In contrast, BNP levels and LVEF did not change in group-B. In Group-A, 15 patients (83%) were classified as LV reverse remodeling despite of 3 patients (37%) in Group-B (P=0.01). Conclusions: These results suggest that long-term increase of intrathoracic impedance is a novel predictor for LV reverse remodeling in CHF patients with CRT.