Background: Identification of individual factors associated with high defibrillation threshold (DFT) seems to be of high clinical importance. Impedance cardiography (ICG) may be used for non-invasive evaluation of the haemodynamic status. Whether ICG parameters may improve identification of patients with high DFT has not yet been examined.
Aim: To evaluate clinical risk factors of high DFT including ICG parameters.
Methods: The study group included 69 patients with heart failure (aged 62.7 ± 9.5 years, NYHA class: I-III) selected for implantation of a cardioverter-defibrillator (ICD). Clinical assessment included physical examination, echocardiography and ICG monitoring before and after defibrillation.
Results: Initial defibrillation was unsuccessful in 17 (36.6%) patients. High DFT group was characterised by higher left ventricular end-diastolic diameter (LVEDD ≥ 5.6 cm: 100.0% vs 70.2%; p = 0.01), lower left ventricular ejection fraction (LVEF < 30%: 76.5% vs 44.7%; p = 0.024), higher baseline thoracic fluid content (one of ICG parameters) (TFC ≥ 35 1/kOhm: 29.4% vs 6.4%; p = 0.014) and more frequent amiodarone treatment (41.2% vs 14.9%; p = 0.025). A proposed algorithm based on predefined values of TFC, LVEF and LVEDD was shown to be effective in predicting high DFT (area under curve: 0.771).
Conclusions: Risk factors of high DFT include left ventricular enlargement, low LVEF, high TFC and amiodarone treatment. An algorithm including TFC measurement by ICG increases the efficacy of identification of patients with high DFT.