Accurate monitoring of intravascular fluid volume: A novel application of intrathoracic impedance measures for the guidance of volume reduction therapy

Abstract

BackgroundA significant proportion of patients admitted for acute decompensated heart failure (ADHF) that undergo volume reduction therapy are discharged with unchanged or increased bodyweight suggesting that the endpoints for these therapies are not optimally defined. We aimed to identify vectors that can help monitor changes in intravascular fluid volume, that in turn may more accurately guide volume reduction therapy.MethodsData from six different impedance vectors and corresponding changes in intravascular volume derived from changes in hematocrit were obtained from 132 clinical congestion events in 56 unique patients enrolled in a multisite trial of early detection of clinical congestion events (DEFEAT PE). Mixed effects regression models were used to determine the relation between changes in impedance derived from six different vectors and changes in intravascular plasma volume.ResultsChanges in impedance were negatively associated with changes in plasma volume. Two vectors, the right atrial ring to left ventricular ring and the left ventricular ring to the right ventricular ring, were most closely associated with changes in intravascular plasma volume.ConclusionImpedance vectors derived from a multivector monitoring system reflect changes in intravascular plasma volume. Two of these vectors most closely track changes in plasma volume and may be used to more accurately guide and optimize volume reduction therapy.

Device‐based remote monitoring strategies for congestion‐guided management of patients with heart failure: a systematic review and meta‐analysis

“…[32][33][34] capacitance gets overwhelmed with initial pulmonary fluid accumulation, which can be detected by a reduction in intrathoracic impedance. 10,21 Finally, this process results in generalized fluid overload with progressive development of symptoms and signs of decompensation leading to hospitalization.…”

“…onset of atrial fibrillation or ventricular tachyarrhythmias, reduction of heart rate variability, and of biventricular pacing rate) 32–34 . Then pulmonary vascular capacitance gets overwhelmed with initial pulmonary fluid accumulation, which can be detected by a reduction in intrathoracic impedance 10,21 . Finally, this process results in generalized fluid overload with progressive development of symptoms and signs of decompensation leading to hospitalization.…”

“… 6 , 7 , 8 Later, the use of invasive devices able to automatically monitor physiological data allowed to continuously check pre‐clinical markers of worsening HF, including congestion parameters such as increased intracardiac or pulmonary artery pressures and pulmonary fluid accumulation. 9 , 10 Remote monitoring strategies of these parameters to allow a prompt and targeted therapeutic response have been tested in various RCTs, often underpowered, which have led to conflicting results. 11 , 12 , 13 , 14 …”

“…[6][7][8] Later, the use of invasive devices able to automatically monitor physiological data allowed to continuously check pre-clinical markers of worsening HF, including congestion parameters such as increased intracardiac or pulmonary artery pressures and pulmonary fluid accumulation. 9,10 Remote monitoring strategies of these parameters to allow a prompt and targeted therapeutic response have been tested in various RCTs, often underpowered, which have led to conflicting results. [11][12][13][14] Previous meta-analyses did not provide unequivocal results as they were selectively performed on a single guided management strategy, 15,16 outcomes or strategies in the same subgroup, [17][18][19] leading to questionable results.…”