Validation of a novel method for non-invasive blood potassium quantification from the ECG

Blood potassium concentration [K⁺] has a strong influence on ECG and particularly on T-wave morphology. We previously developed a method to quantify [K⁺] from ECG analysis. The aims of the study were i) to test this method quantifying [K⁺] on a larger group of hemodialysis (HD) patients ii) to give a mechanical interpretation of the link between [K⁺] and ECG by testing the estimator on congenital LQT2 patients. The ECG-based potassium estimator (K_ECG), based on the ratio between the T-wave descending slope and the T-wave amplitude (T_S/A) was tested on 69 HD sessions (23 patients, 3 sessions each) and on 12 LQT2 patients. ECG recordings were acquired and [K⁺] values were measured from blood samples (K_LAB). The agreement between K_ECG and K_LAB was satisfactory in the HD patients (absolute error: 0.43±0.28mM). The systematic error was very small (0.05mM) while the standard deviation was 0.5mM. As expected, in LQT2 patients our method significantly underestimated [K⁺] (error: 1.15±0.68mM), thus pointing to the I_Kr dependence on extracellular potassium in determining the link between [K⁺] and T-wave morphology. This method could be effectively applied to monitor patients at risk for hyper- and hypokalemia.