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 (KECG), based on the ratio between the T-wave descending slope and the T-wave amplitude (TS/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 (KLAB). The agreement between KECG and KLAB 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 IKr 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.