A real-time system for selectively sensing and pacing the His-bundle during sinus rhythm and ventricular fibrillation

Figures

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  Fig. 1. Block diagram of the complete 96-channel real-time HB sensing, recording, and stimulation system

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  Fig. 2. a Right atrial and upper ventricular septum of a perfused rabbit heart. CSO coronary sinus ostium, KT Koch’s triangle, PB penetrating bundle, TV tricuspid valve. b 64-channel Intellamap Orion basket catheter (Boston Scientific, Marlborough, MA), which was placed in the LV endocardium. c 8 × 8 MappingLab electrode array placed over the region of HB

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  Fig. 3. Pseudo-ECG traces during normal sinus rhythm (top), during HB-pacing with capture (middle), during VM-pacing and captured (bottom). In the top trace, the time interval between two QRS peaks (R–R interval) is 270 ms. When the HB was paced slightly faster than the intrinsic R–R interval with a current amplitude above the threshold, the shape of QRS around the peaks in the middle trace remained very similar to the shape of QRS around the peaks in the top trace. However, the R–R interval in the middle trace now adjusted to the rate of pacing. The stimulation artifacts in the pseudo-ECG in the middle trace are separated by 230 ms (shown). The time lag between the QRS peak and the stimulation artifacts also becomes constant so that t1 = t2 (shown). Similarly, when the VM was paced and captured, t1 = t2. However, unlike the top two traces, the shape of QRS is longer and different

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  Fig. 4. HB capture threshold vs VM capture threshold. The HB capture threshold was significantly smaller than the VM capture threshold (P = 0.033). Note that the standard deviation of the HB pace threshold was quite smaller than the VM pace threshold

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  Fig. 5. Activation maps from basket electrode array during normal sinus rhythm and pacing. Each plot has 8 splines with 8 boxes in each spline, and each box represents an electrode. If the electrode was broken or not in contact with the heart tissue, it was excluded from analysis and the respective electrode box in the above figure is identified by ‘x’. Darker color box indicates earlier activating electrode within a beat. Lighter colors represent later activating electrodes within the same beat. Boxes in the center are towards the apex, and the ones towards outside towards the base. a During sinus, b during sinus rhythm HB pace beat, c during sinus rhythm VM pace beat. Notice that A and B are similar and different from C

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  Fig. 6. Selected traces with prominent atrial signal and prominent HB signal recorded using the real-time stimulation recording system. Arrows in orange point to atrial activations. Arrows in green point to HB activations. Left column: raw traces during normal sinus rhythm (top two) and VF (bottom two). Right column: spatial derivative traces during normal sinus rhythm (top two) and VF (bottom two). All atrial and HB traces are from the same respective electrodes

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  Fig. 7. Preamplifier design a regulators to drop +18 V to 15 V. b Zener diodes used to drop 15 V to 3.3 V, which provides the reference voltage for voltage clipping circuit. c Voltage-to-current converter interfaced with a computer-controlled reed relay switching hardware. The current source signal could be routed to any of the up to 96 channels. d Voltage protection/clipping circuit. e Instrumentation amplifier, amplification, and filtration stages

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  Fig. 8. Description of software for rt-SRS. a The code for rt-SRS consists of two main loops. The producer loop handles codes for data acquisition, recording, activation rate detection, time-precise stimulation, and queues data for consumption in the consumer loop. The consumer loop handles codes for real-time display of raw data or calculation and real-time display of spatial derivative of the raw data. b Flow chart for choosing activations picked closer than a refractory period

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  Fig. 9. The basic waveshape used for pacing consisted of 1-ms positive phase, a 0.2-ms blanking period, and a 1-ms negative phase. The remaining blank period time (t) was determined by the frequency of pacing (F), which may be fixed or determined from the activation rate at an electrode. Amplitude (A) is the current amplitude and is adjustable