Petr Vesely

Classification of ventricular premature and ischemic beats in animal electrograms

Many approaches have been proposed for automatic classification of different pathological events in ECG signals. Present study is focused on analysis and classification of non-ischemic, moderate and severe ischemic, and VPB segments in data obtained in rabbit isolated hearts. It is shown, that use of low number of morphological parameters calculated from electrograms combined with even simple classification method allows achieving of accurate results (with overall accuracy up to 0.99) for four types of the segments.

The effect of voltage sensitive dye di-4-ANEPPS on the RT/RR coupling in rabbit isolated heart

Voltage sensitive dye (VSD) di-4-ANEPPS is ordinary used for optical measurement of action potential in experimental cardiology. In this work, the effect of the dye on the RT/RR coupling measured in electrograms (EG) recorded on rabbit isolated hearts was studied. The results were compared with the control experiments without VSD administration. The comparison was performed in preparation stage of the experiment that consisted of three phases: stabilization (S), VSD loading (L), and washout (W). The median and interquartile range (Q0.75-Q0.25) of the difference in RR, QT and RT/RR between the beginning and the end of the phases were computed and compared between the both groups. Δ(RT/RR), in S, L and W, was -0.095, 0.061; -0.093, 0.043; -0.027, 0.039 in di-4-ANEPPS-treated group and -0.127, 0.071; 0.006, 0.016; -0.001, 0.025 in control group. The significant difference (P<;0.01) was found between two groups in L phase. Additionally, there was the significant difference in ΔRR [ms] which was 120.9, 74.8 in di-4-ANEPPS-treated group and 6.94, 19.28 in control group in the same phase. The significant difference in Δ(RT/RR) between both groups shows a possible effect of di-4-ANEPPS on the RT/RR coupling which is mainly caused by the prolongation of RR interval during loading with the dye.

Repolarization parameters in heart transplant subjects

Heart transplant (HT) patients were analyzed to see whether the QTc depends more on sex of donor or recipient Subjects: 20 male/male (recipient/donor); 21 female/male; 17 female/female; 15 male/female; 23 healthy male; 20 healthy female. Continuous measurement was used over five postural changes: supine, sitting, supine, standing and supine. Results: Significant QTc dependency on the sex of the recipient exists; no dependency on the sex of the donor was found. Heart transplant patients have lower coupling between heart intervals (RR) and QT intervals, lower RR reaction on postural changes and longer QTc than healthy subjects. The only dependency on the sex of the donor was found in heart rate in group of males with female hearts.

The analysis of linear/nonlinear coupling between heart rate and QT intervals

Two groups of subjects (21 healthy, 21 hypertensive patients) were tested during two measurement protocols (exercise, tilt). Two models of QT-RR coupling were tested - linear (LM) and nonlinear (NLM). QTc reproducibility was used as evidence of model validity. Results: LM was significantly better (lower QTc irreproducibility) than NLM (P<;0.01) during the tilt-table test. The differences were not significant during the exercise test; NLM was slightly better in hypertensive patients, LM in healthy subjects. Maximal irreproducibility of QTc over subjects was found in both tests with NLM. Conclusion: Evidence of QT-RR nonlinearity cannot be based on minimal error between QT and model QT. QTc reproducibility must also be tested and the excitation specificity of QT-RR coupling must be considered.

Time-frequency interpretation of ultra-high-frequency QRS components

This paper presents a method for time-frequency representation of ultra-high-frequency components in the QRS complex in high-sensitivity and high-frequency electrocardiography signal measurement. Time-frequency interpretation forms shapes that look like fire - FLAMES. The width, intensity and position of FLAMES characterise the electrical properties of the human heart. FLAMES are able to differentiate electrical changes during asynchronous heart muscle activation and identify changes in electrical activation during heart ischemia, infarctions and structural changes of the myocardium. The difference in FLAMES is demonstrated in healthy young subject and heart-failure subject.