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  • rad51 The OptiVol Fluid Index OVFI


    The OptiVol Fluid Index (OVFI), which is derived from changes in intrathoracic impedance, can effectively assess HF by analyzing the changes in the intrathoracic impedance detected by the original OptiVol algorithm. Small et al. previously determined that a frequent and extended threshold crossing rad51 of OVFI was correlated with actual events of decompensated HF in patients implanted with a cardiac resynchronization therapy with defibrillator (CRT-D) device, and suggested that early prediction of decompensated HF and reduction of hospitalization for HF were possible by monitoring changes in OVFI [3]. Several recent reports, however, have raised concerns about the considerably high false positive rate of decompensated HF events using the original OptiVol algorithm. Ypenburg et al. reported that HF symptoms were actually observed in only 33% of patients in whom OptiVol alerts occurred with the OVFI threshold set at 60Ω [4]. In the Medtronic Impedance Diagnostics in Heart Failure Patients Trial (MIDHEFT), the sensitivity of OVFI in the diagnosis of HF was 77%, and the frequency of non-HF events with OVFI elevation crossing the threshold (false-positive rate) was 1.5 per year per patient [5]. The corresponding results from the Fluid Accumulation Status Trial (FAST) were similar, at 76% and 1.9% per year per patient, respectively [6].
    Discussion In the present study, we collected OptiVol alerts from patients who had a Medtronic ICD/CRT-D implanted and compared the OVFI elevation patterns—the time to peak after crossing the threshold, the duration of threshold crossing, and the peak OVFI value—between true decompensated HF and false-positive events. The results suggested that these OVFI indexes would enhance the diagnostic accuracy of OptiVol fluid status monitoring, while reducing the unexplained threshold crossings that lead to false-positive alerts. In particular, when OVFI has increased slowly and exceeds the threshold for >21 days, or has reached and remained at >136Ω, it is strongly predictive of decompensated HF.
    Conclusions OptiVol alert events based on the original OptiVol algorithm included many false-positive episodes other than decompensated HF, but it was possible to improve the diagnostic accuracy by analyzing the OVFI elevation pattern. Specifically, when OptiVol increases slowly and exceeds the threshold for >21 days, or reaches >136Ω and persists, it is strongly associated with chronic decompensated HF.
    Conflict of interest
    Case report A 77-year-old man with dilated cardiomyopathy visited our hospital in December 2010 and reported dyspnea on effort. Echocardiography revealed cardiac dyssynchrony with a low ejection fraction of 29%, and the patient was diagnosed with New York Heart Association class III heart failure. The plasma N-terminal pro-B-type natriuretic peptide (NT-pro BNP) level was 3691pg/mL. The electrocardiogram (ECG) QRS complex (136ms) was widened to 136ms, with a left bundle branch block conturation (Fig. 1). The patient was being treated with spironolactone (aldactone), β-blocker (carvedilol), and angiotensin II receptor antagonist (captopril). Implantation of a cardiac resynchronization therapy defibrillator (CRT-D) was scheduled and performed in May 2011, without any complications. After implantation of the right ventricular (RV) lead in the RV apex, coronary venography was performed, and a suitable lateral branch was identified as a candidate vessel for left ventricular (LV) lead implantation. The LV lead was positioned at the midportion of the lateral branch. The LV pacing threshold was 0.5mV at 0.5ms without phrenic nerve stimulation. The right atrial (RA) lead was then positioned at the RA appendage. The following device and leads were used: Promote RF generator, Durata 7120Q RV defibrillation lead, QuickFlex 1158T LV lead, and Tendril STS RA lead (St. Jude Medical, St. Paul, Minnesota, USA). The RV pacing threshold was 0.75V at 0.4ms, and the RA pacing threshold was 0.5V at 0.4ms. The device was programmed with a ventricular tachycardia (VT) zone set to ≥166bpm (therapies=antitachy pacing (ATP)×3, shock 10J, 25J, 36J×4) and a ventricular fibrillation (VF) zone set to ≥230bpm (therapies=shock 15J, 36J, 36J×4).