Early detection of cardiac ischemia using a conductometric pCO2 sensor: real-time drift correction and parameterization

For detection of cardiac ischemia based on regional pCO(2) measurement, sensor drift becomes a problem when monitoring over several hours. A real-time drift correction algorithm was developed based on utilization of the time-derivative to distinguish between physiological responses and the drift, customized by measurements from a myocardial infarction porcine model (6 pigs, 23 sensors). IscAlert(TM) conductometric pCO(2) sensors were placed in the myocardial regions supplied by the left anterior descending coronary artery (LAD) and the left circumflex artery (LCX) while the LAD artery was fully occluded for 1, 3, 5 and 15 min leading to ischemia in the LAD-dependent region. The measured pCO(2), the drift-corrected pCO(2) (Delta pCO(2)) and its time-derivative (TDpCO(2)) were compared with respect to detection ability. Baseline stability in the Delta pCO(2) led to earlier, more accurate detection. The TDpCO(2) featured the earliest sensitivity, but with a lower specificity. Combining Delta pCO(2) and TDpCO(2) enables increased accuracy. Suggestions are given for the utilization of the parameters for an automated early warning and alarming system. In conclusion, early detection of cardiac ischemia is feasible using the conductometric pCO(2) sensor together with parameterization methods.