Abstract 2747: Intrathoracic Impedance Monitoring to Predict Decompensated Heart Failure
Introduction: Intrathoracic impedance measurement (OptiVol) has been introduced in the Insync Sentry biventricular ICD (Medtronic Inc.), and can alert the patient when a decrease in impedance indicates pulmonary fluid accumulation secondary to left-sided heart failure. In the present study, we evaluated the clinical value of this OptiVol alert and its prediction for decompensated heart failure.
Methods: One hundred-fifteen consecutive patients (NYHA class 2.8±0.5 and LVEF 26±8%) received an Insync Sentry biventricular ICD. The default alert setting was 60 Ohm.day. When presenting with OptiVol alert, current hemodynamic status was evaluated by history, drug use, physical examination, laboratory tests and chest x-ray.
Results: During follow-up (9±5 months, range 2–18 months), there were 45 presentations with OptiVol alert in 30 patients. Only in 15 cases (33%) clinical signs and symptoms of heart failure were present, whereas in the remaining patients clinical signs of heart failure were absent (P<0.05). ROC curve analysis (Figure⇓) showed that increasing the threshold for OptiVol alert provided a substantial increase in specificity for detection of heart failure, with the optimal cut-off value identified at 120 Ohm.day, yielding a sensitivity of 60% with a specificity of 73%.
Conclusions: Intrathoracic impedance measurement as present in the Insync Sentry biventricular ICD may be a useful tool for monitoring pulmonary fluid status. The proposed threshold for OptiVol alert (60 Ohm.day) is very sensitive but not specific for assessment of heart failure; adjustment of threshold settings may yield a superior balance between sensitivity and specificity.