Noninvasive quantification of blood potassium concentration from ECG in hemodialysis patients

Abstract

Blood potassium concentration ([K+]) influences the electrocardiogram (ECG), particularly T-wave morphology. We developed a new method to quantify [K+] from T-wave analysis and tested its clinical applicability on data from dialysis patients, in whom [K+] varies significantly during the therapy. To elucidate the mechanism linking [K+] and T-wave, we also analysed data from long QT syndrome type 2 (LQT2) patients, testing the hypothesis that our method would have underestimated [K+] in these patients. Moreover, a computational model was used to explore the physiological processes underlying our estimator at the cellular level. We analysed 12-lead ECGs from 45 haemodialysis and 12 LQT2 patients. T-wave amplitude and downslope were calculated from the first two eigenleads. The T-wave slope-to-amplitude ratio (TS/A) was used as starting point for an ECG-based [K+] estimate (KECG). Leave-one-out cross-validation was performed. Agreement between KECG and reference [K+] from blood samples was promising (error: −0.09 ± 0.59 mM, absolute error: 0.46 ± 0.39 mM). The analysis on LQT2 patients, also supported by the outcome of computational analysis, reinforces our interpretation that, at the cellular level, delayed-rectifier potassium current is a main contributor of KECG correlation to blood [K+]. Following a comprehensive validation, this method could be effectively applied to monitor patients at risk for hyper/hypokalemia.

Quantification of hERG Block from the ECG

“…The relationship between this metric and blood plasma potassium concentration suggested that the metric could actually measure outward potassium current. This hypothesis was confirmed by model studies and measurements on LQT2-patients [8]. Incidentally, the same study showed that T S/A was not sensitive to the, sometimes extensive, calcium (Ca) and sodium (Na) concentration changes during the dialysis.…”

“…Besides QT prolongation, classic ECG hallmark of hypokalemia is a reduced T-wave amplitude [6], while the opposite (hyperkalemia) is traditionally diagnosed as tall, peaked T-waves [7]. We recently proposed a metric to quantify the plasma potassium concentration [8], based on the ratio of down-going T-wave slope and T-wave amplitude (T S/A ) and tested it on patients undergoing haemodialysis. The relationship between this metric and blood plasma potassium concentration suggested that the metric could actually measure outward potassium current.…”

ECG as a Tool to Estimate Potassium and Calcium Concentrations in the Extracellular Space

“…Thus, an expansion using more anatomical models is crucial for further evaluation of the findings. In [3], a patient specific calibration is introduced to improve results on patient data. This substantiates a patient-dependency of at least their evaluated feature, but could also mean that a calibration is needed in general.…”

“…However, the ECG as a continuous, non-invasive monitoring tool could shed a light on the relation between heart diseases and changes in the ionic concentration particularly after leaving the strictly supervised clinical area where dialysis takes place, i.e allowing a monitoring at home. Articles have been published showing that the reconstruction of extracellular K + concentration can be done using just one feature from the ECG with a quadratic regression [3]. In this study, we tried to estimate both K + and Ca 2+ concentrations from the ECG.…”

T-Wave Morphology Changes as Surrogate for Blood Potassium Concentration in Hemodialysis Patients

“…Abnormalities in ventricular repolarization are reflected on the electrocardiogram (ECG) signal, in particular, on the T-wave morphology [5]. Different ECG biomarkers have been previously reported to be correlated with [K + ] levels, including the T-wave slope-to-amplitude ratio [6] or the T-wave right slope [7]. However, these biomarkers rely on specific local features of some parts the T-wave, but neglect the information contained in the whole T-wave morphology.…”