This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2019-0370, within PNCDI III.

Procedures involving animal subjects were approved by the Ethics Committee of the University of Medicine, Pharmacy, Science and Technology &#34;George Emil Palade&#34; of T&#226;rgu Mure&#537;, by the Romanian National Sanitary Veterinary and Food Safety Authority and complied with the International Council for Laboratory Animal Science guidelines (Directive 2010/63/EU).
1. Transesophageal atrial burst pacing protocol
<ol>
	<li>Randomize adult male Wistar rats (200-400 g of ...

<ol>
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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atrial+fibrillation+in+rats+induced+by+rapid+transesophageal+atrial+pacing+during+brief+episodes+of+asphyxia:+a+new+in+vivo+model.">Atrial fibrillation in rats induced by rapid transesophageal atrial pacing during brief episodes of asphyxia: a new in vivo model.</a> Journal of Cardiovascular Pharmacology. 44 (1), 125-135 (2004).</li><li>Sugiyama, A., Takahara, A., Honsho, S., Nakamura, Y., Hashimoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+in+vivo+atrial+fibrillation+model+of+rat+induced+by+transesophageal+atrial+burst+pacing.">A simple in vivo atrial fibrillation model of rat induced by transesophageal atrial burst pacing.</a> Journal of Pharmacological Sciences. 98 (3), 315-318 (2005).</li><li>Scridon, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissociation+between+animal+and+clinical+studies.+where+do+we+go+wrong.">Dissociation between animal and clinical studies. where do we go wrong.</a> Romanian Journal of Cardiology. 31 (3), 497-500 (2021).</li><li>Mulla, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+atrial+pacing+promotes+atrial+fibrillation+substrate+in+unanesthetized+instrumented+rats.">Rapid atrial pacing promotes atrial fibrillation substrate in unanesthetized instrumented rats.</a> Frontiers in Physiology. 10, 1218 (2019).</li><li>Scridon, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spontaneous+atrial+fibrillation+after+long-term+transesophageal+atrial+burst+pacing+in+rats.+Technical+and+procedural+approach+to+a+new+in+vivo+atrial+fibrillation+model.">Spontaneous atrial fibrillation after long-term transesophageal atrial burst pacing in rats. Technical and procedural approach to a new in vivo atrial fibrillation model.</a> Romanian Journal of Laboratory Medicine. 26 (1), 105-112 (2018).</li><li>Halatiu, V. 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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoregulatory+disorders+and+illness+related+to+heat+and+cold+stress.">Thermoregulatory disorders and illness related to heat and cold stress.</a> Autonomic Neuroscience: Basic and Clinical. 196, 91-104 (2016).</li><li>&#536;erban, R. C., Scridon, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Data+linking+diabetes+mellitus+and+atrial+fibrillation-how+strong+is+the+evidence?+From+epidemiology+and+pathophysiology+to+therapeutic+implications.">Data linking diabetes mellitus and atrial fibrillation-how strong is the evidence? From epidemiology and pathophysiology to therapeutic implications.</a> Canadian Journal of Cardiology. 34 (11), 1492-1502 (2018).</li><li>Nishida, K., Michael, G., Dobrev, D., Nattel, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+for+atrial+fibrillation:+clinical+insights+and+scientific+opportunities.">Animal models for atrial fibrillation: clinical insights and scientific opportunities.</a> Europace. 12 (2), 160-172 (2010).</li><li>Qiu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DL-3-n-Butylphthalide+reduces+atrial+fibrillation+susceptibility+by+inhibiting+atrial+structural+remodeling+in+rats+with+heart+failure.">DL-3-n-Butylphthalide reduces atrial fibrillation susceptibility by inhibiting atrial structural remodeling in rats with heart failure.</a> Naunyn-Schmiedeberg's Archives of Pharmacology. 391 (3), 323-334 (2018).</li></ol>

The present paper describes an experimental protocol of long-term transesophageal atrial burst pacing for rapid and efficient induction of AF in rats, suitable for both acute and long-term AF studies. The 10-day stimulation protocol described herein has been successfully used to develop a 'secondary spontaneous AF model' (i.e., a model in which, following a period of AF induction by electrical stimulation, AF develops spontaneously)10. However, the duration of the protocol can vary depending on th...

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice and its incidence and prevalence continue to increase dramatically worldwide1. This arrhythmia affects up to 4% of the world population according to recent studies2. However, given that paroxysmal AF can be asymptomatic and may therefore escape detection, the true prevalence of AF is likely to be much higher than that presented in the literature.
The pathophysiology of AF has been intensely studied. Nevertheless, the underlying mechanisms of this complex arrhythmia remain incompletely elucidated and this reflects in the limited therapeutic options, with questionable efficacy. Animal studies have brought important insights into our understanding regarding AF pathophysiology and therapeutic management. Reentry, one of the main mechanisms involved in AF pathogenesis3, requires a certain mass of myocardial tissue in order to occur. Thus, large animals have generally been preferred in AF studies, whereas, due to the small size of their atria, rodents have long been considered &#39;resistant&#39; to AF. However, the use of large animals is hampered mostly by handling difficulties. Meanwhile, although spontaneous AF has been shown to occur in rats4, long-term follow-up (up to 50 weeks) is required for the arrhythmia to occur in those models5. Models that ensure rapid AF occurrence in small rodents have also been developed. Most often, those models use acute electrical stimulation, often in the presence of other favoring conditions, such as concomitant parasympathetic stimulation or asphyxia, to artificially induce AF6,7. Although efficient, such models do not allow the evaluation of critical AF-related features, such as the progressive electrical, structural, autonomic, or molecular remodeling of the atria, nor the effects of conventional or non-conventional antiarrhythmic drugs on the atrial substrate or on the risk of ventricular pro-arrhythmia8,9.
The present work describes an experimental protocol of long-term transesophageal atrial burst pacing for rapid and efficient induction of AF in rats. The protocol is suitable for both acute and long-term studies and can be successfully used in rats with healthy or remodeled hearts, in the presence of a wide variety of risk factors, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of novel prophylactic and/or therapeutic strategies.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Antisedan (Atipamezole Hydrochloride) 5mg / mL, solution for injection</td>
			<td>Orion Corporation</td>
			<td>06043/4004</td>
			<td>for Rats use 1 mg / kg</td>
		</tr>
		<tr>
			<td>Dormitor (Medetomidine Hydrochloride) 1 mg / mL, solution for injection</td>
			<td>Orion Corporation</td>
			<td>06043/4003</td>
			<td>for Rats use 0.5 mg / kg</td>
		</tr>
		<tr>
			<td>E-Z Anesthesia Single Animal System</td>
			<td>E-Z Systems Inc</td>
			<td>EZ-SA800</td>
			<td>Allows the manipulation of one animal at a time</td>
		</tr>
		<tr>
			<td>Isoflurane 99.9%, 100 mL</td>
			<td>Rompharm Company</td>
			<td>N01AB06</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine 10%, 25 mL</td>
			<td></td>
			<td></td>
			<td>for Rats use 75 mg / kg</td>
		</tr>
		<tr>
			<td>Microcontroller-based cardiac pacemaker for small animals</td>
			<td></td>
			<td></td>
			<td>Developed in our laboratory (See Reference number 10 in the manuscript)</td>
		</tr>
		<tr>
			<td>Surface ECG recording system</td>
			<td></td>
			<td></td>
			<td>Developed in our laboratory (See Reference number 10 in the manuscript)</td>
		</tr>
	</tbody>
</table>

transesophageal atrial burst pacing for atrial fibrillation induction in rats

Animal studies have brought important insights into our understanding regarding atrial fibrillation (AF) pathophysiology and therapeutic management. Reentry, one of the main mechanisms involved in AF pathogenesis, requires a certain mass of myocardial tissue in order to occur. Due to the small size of the atria, rodents have long been considered 'resistant' to AF. Although spontaneous AF has been shown to occur in rats, long-term follow-up (up to 50 weeks) is required for the arrhythmia to occur in those models. The present work describes an experimental protocol of transesophageal atrial burst pacing for rapid and efficient induction of AF in rats. The protocol can be successfully used in rats with healthy or remodeled hearts, in the presence of a wide variety of risk factors, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of novel prophylactic and/or therapeutic strategies.

In a proof-of-concept study, 22 adult male Wistar rats (200-400 g) were randomly assigned into two groups: STIM (n = 15) and SHAM (n = 7). All animals were housed individually in polycarbonate cages, in a climate-controlled room (21-22 &#176;C), having free access to water and dry food throughout the study. The transesophageal stimulation protocol described above was applied to all animals for 10 days, 5 days per week. All animals underwent the same protocol, except that the rats in the SHAM group did not receive active ...

Watch this Scientific Journal Video about Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats at JoVE.com

Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats

The present work describes an experimental protocol of transesophageal atrial burst pacing for efficient induction of atrial fibrillation (AF) in rats. The protocol can be used in rats with healthy or remodeled hearts, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of new therapeutic strategies.

Animal studies have brought important insights into our understanding regarding atrial fibrillation (AF) pathophysiology and therapeutic management. ...

The present protocol can be successfully used in rats with healthy or remodeled hearts in the presence of a wide variety of risk factors for acute or long-term follow up studies. This protocol allows studying atrial fibrillation in different pathophysiological conditions to evaluate novel prophylactic and therapeutic strategies. After anesthetizing an adult wistar rat, place the rat in a supine position on a heating pad to maintain its body temperature at 37 degrees Celsius.Then, attach three surface ECG electrodes to the rat limbs in a lead II configuration by placing the negative electrode on the right forelimb, the positive electrode on the left hindlimb, and the grounding electrode on the left forelimb. Secure the electrodes into position using thin elastic bracelet string chords. Next, turn on the surface ECG recording and perform continuous ECG recording throughout the procedure using a commercial or a locally developed acquisition program.For electrical stimulation, use a five or six French quadripolar catheter connected to a microcontroller-based cardiac pacemaker. Once the route is fully anesthetized, insert the catheter through the oral cavity into the esophagus. To confirm the correct position of the stimulation catheter at the level of the atria, apply electrical stimulation at a frequency of 400 stimuli per minute.Then, check whether the ECG tracing shows constant capture of the atria. Based on this, determine the diastolic threshold defined as the lowest voltage required to obtain atrial capture. For rats in the stimulation group, once the correct position of the catheter is determined, set the stimulator to a frequency of 4, 000 stimuli per minute at a voltage of three volts above the diastolic threshold.Then, for each rat, apply 15 successive cycles of stimulation, 20 seconds each, with a free interval of five minutes between cycles. Next, check the effectiveness of the stimulation by identifying the sinus node recovery time, which appears at the end of the rapid pacing as a time interval that is longer than the cycle length recorded during sinus rhythm and represents the interval of time required for resumption of sinus rhythm after overdrive suppression ends. Then, identify the occurrence of the atrial fibrillation episode defined as the presence of three or more consecutive, irregular, supraventricular beats with P-waves absent or replaced by small, distorted F-waves.For rats in the sham group, after inserting the catheter through the oral cavity, maintain the catheter in position for 18 minutes without applying any electrical stimulation, while continuously recording the surface ECG. On the first day of stimulation, 80%of the rats that received electrical stimulation presented atrial fibrillation episodes Out of the applied 164 stimulation cycles, 42 were followed by atrial fibrillation episodes. During the 10 days of stimulation, on average, 15.6 atrial fibrillation episodes were efficiently induced in all animals.Of the total stimulation cycles applied, 20%were followed by atrial fibrillation and 41 episodes lasted more than 600 seconds. For episodes lasting less than 600 seconds, the average duration was 40.12 seconds. The present technique is relatively easy to reproduce and no special training is required for laboratory personnel who regularly work with animal models.Following this procedure, continuous ECG recording using a telemetry device can be performed to assess spontaneous atrial fibrillation episodes and heart rate variability.

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2.8K Views.  University of Medicine, Pharmacy, Science and Technology “George Emil Palade” of Târgu Mureș. The present protocol can be successfully used in rats with healthy or remodeled hearts in the presence of a wide variety of risk factors for acute or long-term follow up studies. This protocol allows studying atrial fibrillation in different pathophysiological conditions to evaluate novel prophylactic and therapeutic strategies. After anesthetizing an adult wistar rat, place the rat in a supine position on a heating pad to maintain its body temperature at 37 degrees Celsius.Then, attac...