Application of Insertable Cardiac Monitor in Establishing a Dog Model of Atrial Fibrillation by High-Frequency Right Atrial Pacing

Figures

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  Figure 1. Establishment of high-frequency right atrial pacing in dogs. (A) Puncture the right external jugular vein and insert the guide wire. (B) Implant the 3830 electrode wire through Select Site™ sheath system. (C) The parameters of pacemaker electrodes were measured by connecting detector across bridge line. (D) Pacing electrode parameters were examined during operation. (E) Pacemaker is connected to the pacemaker electrode. (F) The pacemaker was placed in the anterolateral cervical pouch. (G) Stitch the wound of pacemaker pocket. (H) Bandaging the incision of Pacemaker pouch. (I) The images suggest that the right atrial pacing system has been successfully established.

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  Figure 2. Implantation of Reveal LINQ. (A) The experimental dog was placed in the supine position on the operating table. The implantation site was located between the fourth and fifth ribs of the chest, 2 cm from the left margin of the median line. (B) A skin incision was made with a special scalpel. (C) The subcutaneous tissues were separated with a separating tool. (D) The subcutaneous tissues separated by the separating tool formed an implantation pathway. (E) The insertable cardiac monitor Reveal LINQ to be implanted was injected with matching injection tools. (F) Reveal LINQ was successfully established.

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  Figure 3. Electrocardiography (ECG) during and after the establishment of the atrial fibrillation (AF) model. (A, B) ECGs were performed before the operation of the experimental dogs, showing a sinus rhythm. (C, D) AF models were established by rapid atrial pacing. (E, F) In the establishment of the AF model, the atrial stimulation frequency of the pacemaker in the high-frequency AF model was 500 beats per minute. After closing the pacing function of the pacemaker, ECG showed a sinus rhythm, tachycardia and peaked P waves. (G, H) AF models were successfully established. The ECG showed that the P wave disappeared and was replaced by an irregular tremor wave with an irregular size, shape and time limit, and an irregular ventricular rhythm.

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  Figure 4. Atrial fibrillation (AF) events recorded by Reveal LINQ. When an experimental dog implanted with Reveal LINQ is programmed as AF only, during the monitoring period, the AF burden is 44.1%.The episode duration of AF indicates that it is paroxysmal AF.

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  Figure 5. The areas of left atrium and right atrium were measured by echocardiography. (A1, A2) Measurement of the left atrial area; (B1, B2) Measurement of the right atrial area.

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  Figure 6. Pathological changes of atrial myocardial cells observed under a light microscope (400×). In the Control group (A1, B1) the cardiomyocytes in the left atrium were structurally intact, neatly arranged, with clear nuclei, and filled with regular fiber network. In the AF group, (A2) cardiomyocytes were obviously necrotic, with loose intercellular substance, vacuolar degeneration, and granular degeneration, (B2) fibrosis change of intercellular substance.

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  Figure 7. Observations of the ultrastructure of the left atrial myocardial cells in the Control group (A1, A2) and atrial fibrillation (AF) group (B1, B2) by electron microscopy. In the Control group, the myofibrils of left atrial myocytes were arranged orderly, and the chromatin structure of nuclear membrane was normal. In the AF group, the ultrastructure of the left atrial myocytes was obviously abnormal, with severe degeneration of myofibrillary, severe shrinkage of the nucleus, apoptosis of cells, enlargement of endoplasmic reticulum, and disorder of muscle fibers accompanied by disintegration of some muscle filaments.