Abstract 4857: Significance of Intra-Thoracic Impedance Change as a Marker of Impaired Prognosis after Cardiac Resynchronization Therapy: From a Worldwide Clinical Trial
Measurement of intra-thoracic impedance (TI) change has been studied for the detection of heart failure exacerbation by estimating the pulmonary fluid retention status. The correlation of TI change and the adverse event (AE) after cardiac resynchronization therapy (CRT) was evaluated. In Concerto™ CRT-D (Medtronic, MN), the cumulative decrease of daily TI value crossing a pre-set threshold can be recorded as a threshold crossing (TC) event by the OptiVol® feature. The occurrence of TC events and AE were analyzed in consecutive 282 subjects (201 males; mean age 66.9±11.5; NYHA III: 93%, IV: 7%). All new or worsening AE information was collected throughout the study duration. The reports of AE and serious AE (SAE), reviewed and determined by an independent global adverse event advisory committee (AEAC), were used for analysis. The TI feature was active in all patients with the nominal threshold value at 60 ohm.days. During the follow-up period of 10.0±3.2 (range: 1 to 16) months, 145 patients experienced at least one TC event (TC(+) group) while 137 patients did not have TC (TC(−) group). The prevalence of AE with respect to the occurrence of TC is presented in the table⇓. A trend was observed of higher prevalence of heart failure (HF)-related hospitalization and AE in the TC(+) group. Patients reported with arrhythmic events were equal in both groups. The prevalence of any SAE adjudicated by the AEAC was significantly higher in the TC(+) group with a sensitivity of 58.3% (p=0.02). These SAE included non-HF-related events such as renal failure, pneumonia, acute myocardial infarction etc. Abrupt change in TI was associated with not only cardiac events but also worsening of all medical condition after CRT. These suggest that the measures of TI may be a useful marker for the detection of the prognosis in endstage HF patients.