Noninvasive potassium determination using a mathematically processed ECG: Proof of concept for a novel “blood-less, blood test”

• Serum potassium can be reliably estimated using mathematical algorithms for processing signal-averaged ECGs.
• Potassium changes as small as 0.2 mmol/L were detectable.
• Potassium could be measured within and near the normal range.
• Initial, individual correlation of potassium with the ECG is required.

ObjectiveTo determine if ECG repolarization measures can be used to detect small changes in serum potassium levels in hemodialysis patients.Patients and MethodsSignal-averaged ECGs were obtained from standard ECG leads in 12 patients before, during, and after dialysis. Based on physiological considerations, five repolarization-related ECG measures were chosen and automatically extracted for analysis: the slope of the T wave downstroke (T right slope), the amplitude of the T wave (T amplitude), the center of gravity (COG) of the T wave (T COG), the ratio of the amplitude of the T wave to amplitude of the R wave (T/R amplitude), and the center of gravity of the last 25% of the area under the T wave curve (T4 COG) (Fig. 1).ResultsThe correlations with potassium were statistically significant for T right slope (P < 0.0001), T COG (P = 0.007), T amplitude (P = 0.0006) and T/R amplitude (P = 0.03), but not T4 COG (P = 0.13). Potassium changes as small as 0.2 mmol/L were detectable.ConclusionSmall changes in blood potassium concentrations, within the normal range, resulted in quantifiable changes in the processed, signal-averaged ECG. This indicates that non-invasive, ECG-based potassium measurement is feasible and suggests that continuous or remote monitoring systems could be developed to detect early potassium deviations among high-risk patients, such as those with cardiovascular and renal diseases. The results of this feasibility study will need to be further confirmed in a larger cohort of patients.