Intra-thoracic Impedance and the Onset of Atrial and Ventricular Tachyarrhythmias: A Meta-analysis

Background and purpose: Advances of implantable cardioverter–defibrillator (ICD) devices allow correlating changes in the intra-thoracic impedance (TI), an indicator of fluid overload, with the onset of arrhythmic events. In an attempt to attain a better understanding of this relationship, we conducted a meta-analysis of studies that investigated the association between TI changes and the onset of AT/AF and/or VT/VF in patients with ICD devices. Methods: We performed a meta-analysis of studies published through January 2017 that reported an association between a decrease in the TI measured by the OptiVol fluid index (OI) and occurrence of AT/AF and VT/VF. We searched four databases: PubMed, Embase, CINAHL and Cochrane. Effect estimates were extracted from each study in the form of odds ratio (OR) and 95% confidence intervals. Results: We identified 8 articles with results of the original research, allowing us to extract data for the OR calculation. Our pooled sample included 94,666 patients from 4 studies for AT/AF and 23,601 patients from 6 studies for VT/VF. Two studies were included in both analyses. The pooled OR for fluid index threshold crossing of 60 Ω-days was 1.56 (95% CI 1.35, 1.81) for VT/VF and 1.8 (95% CI 1.43, 2.27) for AT/AF. Conclusion: The findings of our meta-analysis based on the large pooled population of > 110,000 patients, reveal that decreased TI (measured by OI threshold crossing of 60 Ω-days) is a significant risk factor for the onset of AT/AF and VT/VF.