Spatial and temporal variability of ECG waveforms observed in sinus rhythm and during atrio-ventricular stimulation in a patient with implanted ICD: case study

Measurements of surface HR ECG were carried out in an unshielded environment. Signals were acquired from one patient with implanted ICD (implantable cardioverter-defibrillator) during sinus rhythm and during atrial and ventricular stimulation. QRS, STT, QRST deflection areas and T wave alternans were studied. Significant differences between two ventricular activation sequences were found in spatial distributions of QRS and STT integrals in comparison to QRST integral maps, of which spatial distribution was almost independent of activation order. Quantification of differences was done with the use of principal component analysis and correlation coefficient between deflection areas of waveforms. Departure maps were also studied. Beat to beat variations of QRS, STT and QRST deflection areas were calculated and compared to microvolt T-wave alternans test results