Research ArticleAtrial Fibrillation

An automated hybrid bioelectronic system for autogenous restoration of sinus rhythm in atrial fibrillation

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Science Translational Medicine  27 Feb 2019:
Vol. 11, Issue 481, eaau6447
DOI: 10.1126/scitranslmed.aau6447
  • Fig. 1 Functional right atrial ReaChR expression after gene painting.

    (A) Representative photographs of the RA before and directly after gene painting. AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA particles were applied to the surface of the RA in a fibrinogen solution after which thrombin was added to induce clot formation (pale covering). (B) Representative immunohistological staining of longitudinal sections of the heart for green fluorescent protein (green) and cardiac troponin I (red) (upper left and right panels) showing transgene expression in the RA. Cell nuclei are stained in blue. ReaChR expression was transmural (lower left panel), and the protein was mainly plasma membrane bound (lower right panel). (C) Western blot analysis of ReaChR~citrine expression in the RA, LA, and ventricle (V) in a wild-type (WT) control rat and in a ReaChR-expressing rat 4 weeks after gene painting. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as loading control. (D) Sharp electrode measurement of the ReaChR-expressing RA showing spontaneous action potentials silenced by a 1000-ms light pulse (λ = 470 nm; irradiance, 2.55 mW/mm2) leading to sustained depolarization during illumination. (E) Optical atrial pacing by 470-nm light pulses (blue dots) of the ReaChR-expressing RA resulting in 1:1 atrial capture and ventricular conduction. RV, right ventricle; LV, left ventricle.

  • Fig. 2 Autogenous termination of atrial tachyarrhythmias ex vivo.

    (A) Intracardiac ECG demonstrating termination of an atrial tachyarrhythmia with a single 470-nm light pulse (100 ms, 0.8 mW/mm2, light blue box) illuminating 20 mm2 of the RA. Bipolar ECG needles were attached to the LA and ventricle to visualize both atrial and ventricular electrical activity on a single lead. (B and C) Quantification of light-induced termination of atrial tachyarrhythmias expressed as a percentage of successful attempts averaged for ReaChR-expressing and control hearts for various light pulse intensities and wavelengths (light pulse duration, 1000 ms) (B) or averaged for light pulse duration in ReaChR-expressing hearts only (λ = 470 nm; irradiance, 3.5 mW/mm2) (C). (D) Quantification of optical arrhythmia termination efficacy averaged per ReaChR-expressing heart (n = 4) for various surface areas of illumination (λ = 470 nm; irradiance, 2.0 mW/mm2; light pulse duration, 500 ms). Illumination was repeated up to three times in cases of prior unsuccessful arrhythmia termination. (E) Electrical activation map of a ReaChR-expressing RA, derived from optical voltage recordings, showing a re-entrant conduction pattern during AF and subsequent restoration of sinus rhythm after optogenetic arrhythmia termination. (F) Optical voltage trace showing rapid and chaotic atrial electrical activation during AF, which converts to sinus rhythm with 1:1 ventricular conduction after exposure of the RA to a 100-ms light pulse (λ = 470 nm; irrandiance, 3.5 mW/mm2; light blue box). int., intensity; a.u., arbitrary units. Data are means ± 1 SEM. Each dot represents a minimum of three independent measurements in one heart. ***P ≤ 0.001 by (B) Mann-Whitney U test (n = 4 to 12 hearts per group) or (C) Kruskal-Wallis test with Dunn-Bonferroni post hoc test (n = 5 to 12 hearts per group).

  • Fig. 3 Autogenous termination of AF in vivo.

    (A) Overview of the in vivo open-chest experimental setup showing a mounted 470-nm LED collimation lens directed at the RA after a minithoracotomy and subsequent rib spreading of the fourth right intercostal space. (B) Typical body surface ECG trace showing optical pacing of the RA with 470-nm light pulses (1 ms, 3.5 mW/mm2, blue dots) during 10-Hz pacing resulting in 1:1 ventricular conduction. (C) Typical body surface ECG trace demonstrating successful in vivo light-induced termination of AF and subsequent restoration of sinus rhythm by a single 470-nm light pulse (1000 ms, 3.5 mW/mm2, blue shaded region). (D and E) Quantification of light-induced termination of AF for all ReaChR-expressing hearts and citrine controls, expressed as a percentage of successful attempts averaged for all rats, for various light pulse intensities and wavelengths (light pulse duration, 1000 ms) (D) and various light pulse durations for ReaChR-expressing rats (light intensity, 3.5 mW/mm2) (E). Data are means ± 1 SEM. Each dot represents a minimum of three independent measurements in one rat. *P < 0.05 and ***P ≤ 0.001 by the Mann-Whitney U test (n = 4 to 12 rats per group). For (E), the Kruskal-Wallis test found no significant differences (n = 5 to 12 rats per group; P = 0.178).

  • Fig. 4 Overview of the hybrid bioelectronic system with implantable LED device.

    (A) Schematic diagram of the automated hybrid bioelectronic system consisting of the optogenetically modified RA (green) and a cardiac rhythm monitor. The input of the cardiac rhythm monitor consists of analog body surface ECG signals that are automatically analyzed for rhythm anomalies. Upon detection of sustained AF, an output signal is generated, switching on the implantable LED device for 500 ms and leading to autogenous termination of AF and restoration of sinus rhythm by activation of the light-gated depolarizing ion channels present in the RA. Note that both the input and output of this hybrid bioelectronic system do not depend on physical contact with the heart. (B) Exploded schematic view of the implantable LED assembly. The LED is placed inside the reflector cup at a 90º angle to enable total internal reflection. The surgical suture is shown to illustrate the fixation method. (C) Demonstration of the LED implantation process, before closure of the chest, showing firm fixation of the LED implant to the inside of the thoracic wall of the rat heart at the height of the RA (without making physical contact with the heart). (D) Demonstration of the LED implant during illumination after surgical closure of the thoracic wall, muscle layers, and skin. The electrical wires entering the wound drive the pacing electrode and LED.

  • Fig. 5 Autogenous restoration of sinus rhythm in AF by an automated hybrid bioelectronic system.

    (A) Representative body surface ECG traces showing three consecutive events of successful automated in vivo closed-chest detection and termination of AF by the hybrid bioelectronic system. Upon detection of AF by the custom-made algorithm and expiration of the programmed 10-s delay, the 470-nm LED implant is activated for 500 ms at 3.5 mW/mm2 (blue boxes) resulting in autogenous termination of AF and subsequent restoration of sinus rhythm. Inserts highlight (1) regular sinus rhythm before optical termination of AF, (2) rapid and irregular atrial activity during AF, and (3) regular sinus rhythm after the third of three consecutive and successful attempts of optical AF termination. Note that sinus rhythm is immediately restored after autogenous termination of AF without the occurrence of sinus bradycardia or other arrhythmias. (B) Quantification of optical and spontaneous termination of AF expressed as a percentage averaged for all rats. Also included are the spontaneous termination rate and control experiments. Each dot represents a minimum of five measurements in one rat. The error bar represents 1 SEM. (C) Histogram (bin size, 5 s) of the time to automated LED activation directly after AF onset of all autogenous termination attempts (29 AF episodes in four rats). Because of the programmed delay of 10 s, the LED could not be active in the first 10 s of AF (shaded area). (D) Graph showing the average RR intervals of the last 10 s before AF induction, the first 10 s of AF, and immediately (0 to 5 s) and later (5 to 15 s) after autogenous AF termination. Each line represents one measurement. Data are means. *P < 0.05 and **P < 0.01 by (B) Mann-Whitney U tests (n = 3 to 4 rats per group) or (D) two-sided paired t test (n = 20 AF episodes from four rats per group).

Supplementary Materials

  • www.sciencetranslationalmedicine.org/cgi/content/full/11/481/eaau6447/DC1

    Materials and Methods

    Fig. S1. Maps of the AAVV genomes.

    Fig. S2. Transgene expression in different cardiac compartments after gene painting of the RA of adult rat hearts with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.

    Fig. S3. Transgene expression after gene painting of the RA of adult rat hearts with AAV2/9.45.HsNPPA.citrine.SV40pA.

    Fig. S4. Masson’s trichrome staining of the RA and LA after gene painting of the RA with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.

    Fig. S5. Light intensity–duration curve for optical atrial pacing of adult rat hearts after gene painting of the RA with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.

    Fig. S6. Correlation between surface area and location of right atrial illumination on optogenetic termination of atrial tachyarrhythmias ex vivo.

    Fig. S7. Efficient autogenous termination of atrial flutter in vivo after gene painting of the RA of adult rat hearts with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.

    Fig. S8. Implantable LED device.

    Fig. S9. Schematic overview of the AF detection algorithm and experimental setup.

    Fig. S10. Prolonged illumination of the RA and ventricle of adult rat hearts after gene painting of the RA with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.

    Fig. S11. Ex vivo temperature measurements of the RA during LED activation.

    Fig. S12. Computational simulation of thermal heating after activation of the implantable LED device based on in vivo conditions.

    Data file S1. Raw data.

    Movie S1. Optical voltage mapping of the ReaChR-expressing RA during AF and subsequent optogenetic restoration of sinus rhythm.

    Movie S2. Summary of all essential experimental steps leading to the development of the automated hybrid bioelectronic system for autogenous restoration of sinus rhythm in AF.

  • The PDF file includes:

    • Materials and Methods
    • Fig. S1. Maps of the AAVV genomes.
    • Fig. S2. Transgene expression in different cardiac compartments after gene painting of the RA of adult rat hearts with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.
    • Fig. S3. Transgene expression after gene painting of the RA of adult rat hearts with AAV2/9.45.HsNPPA.citrine.SV40pA.
    • Fig. S4. Masson’s trichrome staining of the RA and LA after gene painting of the RA with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.
    • Fig. S5. Light intensity–duration curve for optical atrial pacing of adult rat hearts after gene painting of the RA with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.
    • Fig. S6. Correlation between surface area and location of right atrial illumination on optogenetic termination of atrial tachyarrhythmias ex vivo.
    • Fig. S7. Efficient autogenous termination of atrial flutter in vivo after gene painting of the RA of adult rat hearts with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.
    • Fig. S8. Implantable LED device.
    • Fig. S9. Schematic overview of the AF detection algorithm and experimental setup.
    • Fig. S10. Prolonged illumination of the RA and ventricle of adult rat hearts after gene painting of the RA with AAV2/9.45.HsNPPA.ReaChR~citrine.SV40pA.
    • Fig. S11. Ex vivo temperature measurements of the RA during LED activation.
    • Fig. S12. Computational simulation of thermal heating after activation of the implantable LED device based on in vivo conditions.
    • Legend for Data file S1
    • Legends for Movies S1 and S2

    [Download PDF]

    Other Supplementary Material for this manuscript includes the following:

    • Data file S1 (Microsoft Excel format). Raw data.
    • Movie S1 (.avi format). Optical voltage mapping of the ReaChR-expressing RA during AF and subsequent optogenetic restoration of sinus rhythm.
    • Movie S2 (.mp4 format). Summary of all essential experimental steps leading to the development of the automated hybrid bioelectronic system for autogenous restoration of sinus rhythm in AF.

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