Real-time vectorcardiography simulator system

Figures

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  Fig 1. Frontal 2D representation of the heart vector. The trajectory of the instantaneous heart vector traces the frontal vectorcardiographic loops, whose projections onto the sides of the Einthoven triangle produce the corresponding electrocardiographic waveforms in Leads I, II, and III.

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  Fig 2. General schematic of the system. Hardware interaction module: container A, a mobile hand electrode B, fixed electrodes C, a sacrifice electrode D, a mini spirit level bubble indicator E, conductive medium (sodium chloride solution) F, and an acrylic flat piece G; Signal acquisition module H; and Data processing and visualization module with ECG waves I, and VCG loops J.

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  Fig 3. General circuitry diagram. The electronic component MAX6018 provides a stable voltage reference for the 16-bit differential ADC in the K64F microcontroller. A MAX4053 multiplexer measures each channel sequentially. System power isolation uses an ITX0505SA DC-DC converter connected to a SWM 12−5 5V adapter.

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  Fig 4. Electrical measurements. Each internodal connection within the conductive medium exhibits electrical impedance behavior that can be approximated by an equivalent circuit consisting of passive elements such as resistors and capacitors.

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  Fig 5. The final vectorcardiography simulator system is shown in operation. According to the technical validation Method 1, here, a user is moving the mobile-hand electrode describing circular trajectories with different radius within the device (see right side of the screen). As expected, the resulting sine waves exhibit different amplitudes in each lead, corresponding to the varying radius of the trajectories (see left side of the screen).

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  Fig 6. System tested with ECG signal from the Physionet database. The ECG waveforms obtained showed a strong agreement with typical healthy ECG waveforms, both in shape and duration (left). In the case of the VCG loops, the outer VCG loop (corresponding to the QRS complex) created by the system faithfully reproduced the typical “oval-like” shape observed in the literature.

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  Fig 7. User-generated ECG waveforms and DTW analysis. A user tested the system by moving the hand mobile electrode to create typical ECG waveforms and VCG loops (down). DTW Analysis of User-generated vs. ECG database waveforms (top): (a) ECG database reference (blue) and User-generated (gray) waveforms showing differences in amplitude and timing. (b) DTW alignment visualization, where gray lines connect corresponding points between the reference and the user signal (shifted vertically for clarity). (c) Accumulated cost matrix with the optimal warping path (white line) and the resulting similarity metrics: Similarity 84% and Normalized DTW 0.0153.