Name: transesophageal atrial burst pacing for atrial fibrillation induction in rats
Uploaded: 2022-02-14T15:00:00.000+00:00
Duration: 5 min 12 s
Description: Watch this Scientific Journal Video about Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats at JoVE.com

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 bodyweight) into two groups: STIM and SHAM.</li>
	<li>Anesthetize the animals.
	<ol>
		<li>For induction, use 2.5% isoflurane, 4 L/min, 99.5% O2.</li>
		<li>For maintenance, use a mixture of ketamine/medetomidine (75.0/0.5 mg/kg) administered intraperitoneally.</li>
		<li>Check the depth of the anesthesia by testing the corneal reflex (5% glucose solution) and the nociceptive withdrawal reflex (toe pinch). Monitor the respiratory rate (a fall of 50% is acceptable during anesthesia; normal rate is between 70-120 breaths/minute) and the body temperature using a rectal thermometer (normal temperature is between 96.5 - 99.5 &#176;F or 35.9 - 37.5 &#176;C). 
		NOTE: Continue the procedure only after the effectiveness of anesthesia is confirmed. Monitor the depth of anesthesia periodically throughout the protocol. Repeat the intraperitoneal ketamine/medetomidine injection when needed.</li>
		<li>Apply an ophthalmic ointment to both eyes to prevent corneal damage.</li>
	</ol>
	</li>
	<li>Lay the animal in supine position and place it on a heating pad to maintain body temperature at ~37 &#176;C.</li>
	<li>Attach the three surface ECG electrodes to the rat limbs in a lead II configuration (Figure 1A).
	<ol>
		<li>Place the negative electrode on the right forelimb.</li>
		<li>Place the positive electrode on the left hindlimb.</li>
		<li>Place the grounding electrode on the left forelimb.</li>
		<li>Secure the electrodes into position using thin elastic bracelet string cords.</li>
	</ol>
	</li>
	<li>Turn on the surface ECG recording and perform continuous ECG recording throughout the procedure (Figure 1B) using a commercial or a locally developed acquisition program10.</li>
	<li>For electrical stimulation, use a 5-6 F quadripolar catheter connected to a microcontroller-based cardiac pacemaker10.</li>
	<li>Once the animal is anesthetized, insert the catheter through the oral cavity, into the esophagus. Measure the distance between the upper incisors and the heart (assessed by palpation) to approximate the depth at which the catheter should be inserted into the esophagus. 
	CAUTION: Be careful not to force the catheter as there is a risk of esophageal perforation.</li>
	<li>Confirm the correct position of the stimulation catheter at the level of the atria as follows.
	<ol>
		<li>Apply electrical stimulation at a frequency of 400 stimuli/minute (stimulus duration 6 ms).</li>
		<li>Check whether the ECG tracing shows constant capture of the atria (i.e., each electrical stimulus is followed by a narrow QRS complex) (Figure 2).</li>
	</ol>
	</li>
	<li>Determine the diastolic threshold&#8212;i.e., the lowest voltage required to obtain atrial capture (generally, between 10 V and 20 V). 
	NOTE: Perform the following for the animals in the STIM group.</li>
	<li>Once the correct position of the catheter is determined, set the stimulator to a frequency of 4,000 stimuli/minute (stimulus duration 6 ms), at a voltage 3 V above the diastolic threshold (Figure 3).</li>
	<li>Apply to each animal 15 successive cycles of stimulation, 20 s each, with a free interval of 5 min between cycles11. Depending on the study objectives, repeat the protocol for each rat for 10 days, at a rate of 5 days/week, at the same time on each day.</li>
	<li>Check the effectiveness of the stimulation as follows.
	<ol>
		<li>Identify the sinus node recovery time (SNRT), which appears at the end of the rapid pacing as a time interval that is longer than the cycle length recorded during sinus rhythm (Figure 4A) and represents the interval of time required for resumption of sinus rhythm after overdrive suppression ends. 
		NOTE: Overdrive suppression represents the inhibition of sinus node activity by electrically stimulating the heart at a rate higher than the intrinsic rhythm.</li>
		<li>Identify the occurrence of the AF episode, which is defined here as the presence of three or more consecutive irregular, supraventricular beats (i.e., irregular ventricular response with narrow QRS complexes), with P-waves absent or replaced by small, distorted &#34;f&#34; waves (Figure 4B).</li>
	</ol>
	</li>
	<li>If the AF episode does not end spontaneously by the time the next stimulation cycle should be performed (i.e., by the end of the five free minutes between cycles), do not apply the next stimulation.
	<ol>
		<li>Wait for another 5 min. If the AF episode still continues after those 10 min, end the protocol for that day. 
		NOTE: If evaluation of the severity of electrically-induced AF is desired, longer ECG monitoring can be performed.</li>
	</ol>
	</li>
	<li>If severe bradycardia or asystole occurs at the end of the stimulation (i.e., due to electrical stimulation of the vagus nerve), end the protocol. If the electrical activity does not return to normal rapidly, perform external cardiac massage and administer atropine sulfate (0.05 mg/kg) intraperitoneally.</li>
	<li>At the end of the procedure, reverse the anesthesia with atipamezole (1 mg/kg) administered intraperitoneally. House the rats individually in clean cages with supplemental heat and observe periodically until they are fully recovered. No other specific animal care is required at the end of the protocol.</li>
	<li>Analyze the surface ECG tracings and determine the following.
	<ol>
		<li>The inducibility of AF which is expressed in percentage (i.e., [number of stimulation cycles followed by AF episodes / total number of stimulation cycles applied] x 100).</li>
		<li>The duration of each AF episode.</li>
		<li>The presence of &#39;persistent&#39; (i.e., &#62;10 min) AF episodes. 
		NOTE: Perform the following for the animals in the SHAM group.</li>
	</ol>
	</li>
	<li>For the rats in the SHAM group, follow steps 1.1 to 1.7 as described above, without applying any electrical stimulation.</li>
	<li>Maintain the catheter into position for 80 min (i.e., the time required for completing the protocol in STIM rats) without applying any electrical stimulation, while continuously recording the surface ECG.</li>
	<li>At the end of the procedure, reverse the anesthesia with atipamezole (1 mg/kg). No other specific animal care is required at the end of the protocol.</li>
	<li>Analyze the surface ECG tracings and determine the parameters described in step 1.16.</li>
</ol>

<ol>
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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=Atrial+arrhythmia+in+ageing+spontaneously+hypertensive+rats:+unraveling+the+substrate+in+hypertension+and+ageing.">Atrial arrhythmia in ageing spontaneously hypertensive rats: unraveling the substrate in hypertension and ageing.</a> PloS One. 8 (8), 72416 (2013).</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=Unprovoked+atrial+tachyarrhythmias+in+aging+spontaneously+hypertensive+rats:+The+role+of+the+autonomic+nervous+system.">Unprovoked atrial tachyarrhythmias in aging spontaneously hypertensive rats: The role of the autonomic nervous system.</a> American Journal of Physiology-Heart and Circulatory Physiology. 303 (3), 386-392 (2012).</li><li>Haugan, K., Lam, H. R., Knudsen, C. B., Petersen, J. 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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. B., 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=Chronic+exposure+to+high+doses+of+bisphenol+A+exhibits+significant+atrial+proarrhythmic+effects+in+healthy+adult+rats.">Chronic exposure to high doses of bisphenol A exhibits significant atrial proarrhythmic effects in healthy adult rats.</a> Romanian Journal of Cardiology. 31 (3), 587-595 (2021).</li><li>Zaciragi&#263;, A., Nakas-i&#263;indi&#263;, E., Hadzovi&#263;, A., Avdagi&#263;, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Average+values+of+electrocardiograph+parameters+in+healthy,+adult+Wistar+rats.">Average values of electrocardiograph parameters in healthy, adult Wistar rats.</a> Medical Archives. 58 (5), 268-270 (2004).</li><li>Cheshire, W. 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 authors have no conflicts of interest.

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><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. ...

transesophageal-atrial-burst-pacing-for-atrial-fibrillation-induction

Universidad de Cartagena UDEC

Research

JoVE Journal

Medicine

3.0K Views.  University of Medicine, Pharmacy, Science and Technology “George Emil Palade” of Târgu Mureș. 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.

Video: Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats

Programmed Electrical Stimulation in Mice

Genetically-modified mice have emerged as a preferable animal model to study the molecular mechanisms underlying conduction abnormalities, atrial and ventricular arrhythmias, and sudden cardiac death.1 Intracardiac pacing studies can be performed in mice using a 1.1F octapolar catheter inserted into the jugular vein, and advanced into the right atrium and ventricle. Here, we illustrate the steps involved in performing programmed electrical stimulation in mice. Surface ECG and intracardiac electrograms are recorded simultaneously in the atria, atrioventricular junction, and ventricular myocardium, whereas intracardiac pacing of the atrium is performed using an external stimulator. Thus, programmed electrical stimulation in mice provides unique opportunities to explore molecular mechanisms underlying conduction defects and cardiac arrhythmias.

Programmed electrical stimulation provides the ability to determine conduction properties of the heart, and the possibility to induce and terminate cardiac arrhythmias using various pacing protocols. Using a transvenous catheter, intracardiac electrogram recordings can be obtained in mice following programmed electrical stimulation protocols to identify arrhythmogenic substrates.

Genetically-modified mice have emerged as a preferable animal model to study the molecular mechanisms underlying conduction abnormalities, atrial and ...

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance seen in clinical practice and its prevalence is expected to increase in the coming years.3 Increased intra-atrial pressure and dilatation have been long recognized to lead to AF,1,4 which highlights the relevance of using animal models and stretch to study AF dynamics. Understanding the mechanisms underlying AF requires visualization of the cardiac electrical waves with high spatial and temporal resolution. While high-temporal resolution can be achieved by conventional electrical mapping traditionally used in human electrophysiological studies, the small number of intra-atrial electrodes that can be used simultaneously limits the spatial resolution and precludes any detailed tracking of the electrical waves during the arrhythmia. The introduction of optical mapping in the early 90's enabled wide-field characterization of fibrillatory activity together with sub-millimeter spatial resolution in animal models5,6 and led to the identification of rapidly spinning electrical wave patterns (rotors) as the sources of the fibrillatory activity that may occur in the ventricles or the atria.7-9 Using combined time- and frequency-domain analyses of optical mapping it is possible to demonstrate discrete sites of high frequency periodic activity during AF, along with frequency gradients between left and right atrium. The region with fastest rotors activates at the highest frequency and drives the overall arrhythmia.10,11 The waves emanating from such rotor interact with either functional or anatomic obstacles in their path, resulting in the phenomenon of fibrillatory conduction.12 Mapping the endocardial surface of the posterior left atrium (PLA) allows the tracking of AF wave dynamics in the region with the highest rotor frequency. Importantly, the PLA is the region where intracavitary catheter-based ablative procedures are most successful terminating AF in patients,13 which underscores the relevance of studying AF dynamics from the interior of the left atrium. Here we describe a sheep model of acute stretch-induced AF, which resembles some of the characteristics of human paroxysmal AF. Epicardial mapping on the left atrium is complemented with endocardial mapping of the PLA using a dual-channel rigid borescope c-mounted to a CCD camera, which represents the most direct approach to visualize the patterns of activation in the most relevant region for AF maintenance.

This report provides a detailed description of the methodology and results of simultaneous endocardial and epicardial optical mapping of electrical excitation in the intact left atrium of a Langendorff-perfused sheep heart during stretch-induced atrial fibrillation.

 Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance ...

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic components of cardiopulmonary resuscitation in humans is herein described. The model was developed in 1988 and has been used in approximately 70 peer-reviewed publications examining a myriad of resuscitation aspects including its physiology and pathophysiology, determinants of resuscitability, pharmacologic interventions, and even the effects of cell therapies. The model featured in this presentation includes: (1) vascular catheterization to measure aortic and right atrial pressures, to measure cardiac output by thermodilution, and to electrically induce ventricular fibrillation; and (2) tracheal intubation for positive pressure ventilation with oxygen enriched gas and assessment of the end-tidal CO2. A typical sequence of intervention entails: (1) electrical induction of ventricular fibrillation, (2) chest compression using a mechanical piston device concomitantly with positive pressure ventilation delivering oxygen-enriched gas, (3) electrical shocks to terminate ventricular fibrillation and reestablish cardiac activity, (4) assessment of post-resuscitation hemodynamic and metabolic function, and (5) assessment of survival and recovery of organ function. A robust inventory of measurements is available that includes &#8211; but is not limited to &#8211; hemodynamic, metabolic, and tissue measurements. The model has been highly effective in developing new resuscitation concepts and examining novel therapeutic interventions before their testing in larger and translationally more relevant animal models of cardiac arrest and resuscitation.

This article describes a rat model of electrically-induced ventricular fibrillation and resuscitation by chest compression, ventilation, and delivery of electrical shocks that simulates an episode of sudden cardiac arrest and conventional cardiopulmonary resuscitation. The model enables gathering insights on the pathophysiology of cardiac arrest and exploration of new resuscitation strategies.

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic ...

Testing the Efficacy of Pharmacological Agents in a Pericardial Target Delivery Model in the Swine

To date, many pharmacological agents used to treat or prevent arrhythmias in open-heart cases create undesired systemic side effects. For example, antiarrhythmic drugs administered intravenously can produce drops in systemic pressure in the already compromised cardiac patient. While performing open-heart procedures, surgeons will often either create a small port or form a pericardial cradle to create suitable fields for operation. This access yields opportunities for target pharmacological delivery (antiarrhythmic or ischemic preconditioning agents) directly to the myocardial tissue without undesired side effects.
We have developed a swine model for testing pharmacological agents for target delivery within the pericardial fluid. While fully anesthetized, each animal was instrumented with a Swan-Ganz catheter as well as left and right ventricle pressure catheters, and pacing leads were placed in the right atrial appendage and the right ventricle. A medial sternotomy was then performed and a pericardial access cradle was created; a plunge pacing lead was placed in the left atrial appendage and a bipolar pacing lead was placed in the left ventricle. Utilizing a programmer and a cardiac mapping system, the refractory period of the atrioventricular node (AVN), atria and ventricles was determined. In addition, atrial fibrillation (AF) induction was produced utilizing a Grass stimulator and time in AF was observed. These measurements were performed prior to treatment, as well as 30 min&#160;and 60 min&#160;after pericardial treatment. Additional time points were added for selected studies. The heart was then cardiopleged and reanimated in a four chamber working mode. Pressure measurements and function were recorded for 1 hr after reanimation. This treatment strategy model allowed us to observe the effects of pharmacological agents that may decrease the incidence of cardiac arrhythmias and/or ischemic damage, during and after open-heart surgery.

We have developed a swine model for the target delivery of pharmacological agents within the pericardial space/fluid. Using this approach, the relative benefits of administered agents on induced atrial fibrillation, relative refractory periods and/or ischemic protection can be investigated.

To date, many pharmacological agents used to treat or prevent arrhythmias in open-heart cases create undesired systemic side effects. For example, ...

Electrophysiological Assessment of Murine Atria with High-Resolution Optical Mapping

Recent genome-wide association studies targeting atrial fibrillation (AF) have indicated a strong association between the genotype and electrophysiological phenotype in the atria. That encourages us to utilize a genetically-engineered mouse model to elucidate the mechanism of AF. However, it is difficult to evaluate the electrophysiological properties in murine atria due to their small size. This protocol describes the electrophysiological evaluation of atria using an optical mapping system with a high temporal and spatial resolution in Langendorff perfused murine hearts. The optical mapping system is assembled with dual high-speed complementary metal oxide semiconductor cameras and high magnification objective lenses, to detect the fluorescence of a voltage-sensitive dye and Ca2+ indicator. To focus on the assessment of murine atria, optical mapping is performed with an area of 2 mm &#215; 2 mm or 10 mm x 10 mm, with a 100 &#215; 100 resolution (20 &#181;m/pixel or 100 &#181;m/pixel) and sampling rate of up to 10 kHz (0.1 ms) at maximum. A 1-French size quadripolar electrode pacing catheter is placed into the right atrium through the superior vena cava avoiding any mechanical damage to the atrium, and pacing stimulation is delivered through the catheter. An electrophysiological study is performed with programmed stimulation including constant pacing, burst pacing, and up to triple extrastimuli pacing. Under a spontaneous or pacing rhythm, the optical mapping recorded the action potential duration, activation map, conduction velocity, and Ca2+ transient individually in the right and left atria. In addition, the programmed stimulation also determines the inducibility of atrial tachyarrhythmias. Precise activation mapping is performed to identify the propagation of the excitation in the atrium during an induced atrial tachyarrhythmia. Optical mapping with a specialized setting enables a thorough electrophysiological evaluation of the atrium in murine pathological models.

This protocol describes the electrophysiological evaluation of murine atria utilizing an optical mapping system with a high temporal and spatial resolution, including dual recordings of the membrane voltage and Ca2+ transient under programmed stimulation through a specialized electrode catheter.

Recent genome-wide association studies targeting atrial fibrillation (AF) have indicated a strong association between the genotype and ...

Sterile Pericarditis in Aachener Minipigs As a Model for Atrial Myopathy and Atrial Fibrillation

Atrial fibrillation (AF) is the most common arrhythmia caused by structural remodeling of the atria, also called atrial myopathy. Current therapies only target the electrical abnormalities and not the underlying atrial myopathy. For the development of novel therapies, a reproducible large animal model of atrial myopathy is necessary. This paper presents a model of sterile pericarditis-induced atrial myopathy in Aachener minipigs. Sterile pericarditis was induced by spraying sterile talcum and leaving a layer of sterile gauze over the atrial epicardial surface. This led to inflammation and fibrosis, two crucial components of the pathophysiology of atrial myopathy, making the atria susceptible to the induction of AF. Two pacemaker electrodes were positioned epicardially on each atrium and connected to two pacemakers from different manufacturers. This strategy allowed for repeated non-invasive atrial programmed stimulation to determine the inducibility of AF at specified time points after surgery. Different protocols to test AF inducibility were used. The advantages of this model are its clinical relevance, with AF inducibility and the rapid induction of inflammation and fibrosis-both present in atrial myopathy-and its reproducibility. The model will be useful in the development of novel therapies targeting atrial myopathy and AF.

We describe a sterile pericarditis model in minipigs to study atrial myopathy and atrial fibrillation (AF). We present surgical and anesthetic techniques, strategies for vascular access, and a protocol to study the inducibility of AF.

Atrial fibrillation (AF) is the most common arrhythmia caused by structural remodeling of the atria, also called atrial myopathy. Current therapies only ...

Translational Rabbit Model of Chronic Cardiac Pacing

Animal models of cardiac pacing are beneficial for testing novel devices, studying the pathophysiology of artificially paced heart rhythms, and studying arrhythmia-induced cardiomyopathies and subsequent heart failure. Currently, only a few such models are available, and they mostly require extensive resources. We report a new experimental cardiac pacing model in small mammals with the potential to study arrhythmia-induced heart failure.
In six New Zealand white rabbits (mean weight: 3.5 kg) under general inhalational anesthesia the jugular region was dissected and a single pacing lead was inserted via the right external jugular vein. Using fluoroscopic guidance, the lead was further advanced to the right ventricular apex, where it was stabilized using passive fixation. A cardiac pacemaker was then connected and buried in a subcutaneous pocket.
The pacemaker implantation was successful with good healing; the rabbit anatomy is favorable for the lead placement. During 6 months of follow-up with intermittent pacing, the mean sensed myocardial potential was 6.3 mV (min: 2.8 mV, max: 12 mV), and the mean lead impedance measured was 744 &#937; (min: 370 &#937;, max: 1014 &#937;). The pacing threshold was initially 0.8 V &#177; 0.2 V and stayed stable during the follow-up.
This present study is the first to present successful transvenous cardiac pacing in a small-mammal model. Despite the size and tissue fragility, human-size instrumentation with adjustments can safely be used for chronic cardiac pacing, and thus, this innovative model is suitable for studying the development of arrhythmia-induced cardiomyopathy and consequent heart failure pathophysiology.

We present a minimally invasive leporine model of long-term cardiac pacing that can be utilized for artificial pacing and heart failure development in preclinical studies.

Animal models of cardiac pacing are beneficial for testing novel devices, studying the pathophysiology of artificially paced heart rhythms, and studying ...

A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts

Ventricular fibrillation (VF) is a fatal arrhythmia with a high incidence in cardiac patients, but VF arrest under perfusion is a neglected method of intraoperative arrest in the field of cardiac surgery. With recent advances in cardiac surgery, the demand for prolonged VF studies under perfusion has increased. However, the field lacks simple, reliable, and reproducible animal models of chronic ventricular fibrillation. This protocol induces long-term VF through alternating current (AC) electrical stimulation of the epicardium. Different conditions were used to induce VF, including continuous stimulation with a low or high voltage to induce long-term VF and stimulation for 5 min with a low or high voltage to induce spontaneous long-term VF. The success rates of the different conditions, as well as the rates of myocardial injury and recovery of cardiac function, were compared. The results showed that continuous low-voltage stimulation induced long-term VF and that 5 min of low-voltage stimulation induced spontaneous long-term VF with mild myocardial injury and a high rate of recovery of cardiac function. However, the low-voltage, continuously stimulated long-term VF model had a higher success rate. High-voltage stimulation provided a higher rate of VF induction but showed a low defibrillation success rate, poor recovery of cardiac function, and severe myocardial injury. On the basis of these results, continuous low-voltage epicardial AC stimulation is recommended for its high success rate, stability, reliability, reproducibility, low impact on cardiac function, and mild myocardial injury.

This protocol presents a model of long-term ventricular fibrillation in rat hearts induced by continuous stimulation with low-voltage alternating current. This model has a high success rate, is stable, reliable, and reproducible, has a low impact on cardiac function, and causes only mild myocardial injury.

Ventricular fibrillation (VF) is a fatal arrhythmia with a high incidence in cardiac patients, but VF arrest under perfusion is a neglected method of ...

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

It is now well recognized that heart failure (HF) patients with left bundle branch block (LBBB) derive substantial clinical benefits from cardiac resynchronization therapy (CRT), and LBBB has become one of the important predictors for CRT response. The conventional tachypacing-induced HF model has several major limitations, including absence of stable LBBB and rapid reversal of left ventricular (LV) dysfunction after cessation of pacing. Hence, it is essential to establish an optimal model of chronic HF with isolated LBBB for studying CRT benefits. In the present study, a canine model of asynchronous HF induced by left bundle branch (LBB) ablation and 4 weeks of rapid right ventricular (RV) pacing is established. The RV and right atrial (RA) pacing electrodes via the jugular vein approach, together with an epicardial LV pacing electrode, were implanted for CRT performance. Presented here are the detailed protocols of radiofrequency (RF) catheter ablation, pacing leads implantation, and rapid pacing strategy. Intracardiac and surface electrograms during operation were also provided for a better understanding of LBB ablation. Two-dimensional speckle tracking imaging and aortic velocity time integral (aVTI) were acquired to validate the chronic stable HF model with LV asynchrony and CRT benefits. By coordinating ventricular activation and contraction, CRT uniformed the LV mechanical work and restored LV pump function, which was followed by reversal of LV dilation. Moreover, the histopathological study revealed a significant restoration of cardiomyocyte diameter and collagen volume fraction (CVF) after CRT performance, indicating a histologic and cellular reverse remodeling elicited by CRT. In this report, we described a feasible and valid method to develop a chronic asynchronous HF model, which was suitable for studying structural and biologic reverse remodeling following CRT.

The establishment of a chronic asynchronous heart failure (HF) model by rapid pacing combined with left bundle branch ablation is presented. Two-dimensional speckle tracking imaging and aortic velocity time integral are applied to validate this stable HF model with left ventricular asynchrony and the benefits of cardiac resynchronization therapy.

It is now well recognized that heart failure (HF) patients with left bundle branch block (LBBB) derive substantial clinical benefits from cardiac ...

Biology

Optimizing Pulmonary Artery Banding for Consistent Right Heart Failure Induction

Rat Model of Right-Sided Cardiac Remodeling and Arrhythmia Using Pulmonary Artery Banding

Clinical conditions, including chronic obstructive pulmonary disease or pulmonary arterial hypertension (PAH), can lead to chronic right ventricle pressure overload and progressive right heart failure (RHF). RHF can be identified by right-sided cardiac hypertrophy and dilation associated with abnormal myocardial function affecting the RV and the right atrium (RA). We recently demonstrated that severe RHF is accompanied by an increased risk of atrial inflammation, atrial fibrosis, and atrial fibrillation (AF), the most common type of cardiac arrhythmia (CA). Recent studies have shown that RV and RA inflammation plays an important role in the arrhythmogenesis of CA, including AF. However, the impact of inflammation in the development of CA and AF in RHF is poorly described.
Experimental models of RHF are required to better understand the association between right-sided myocardial inflammation and CA. The rat model of monocrotaline (MCT)-induced pulmonary hypertension (PH) is well-established to provoke RHF. However, MCT triggers severe pneumo-toxicity and pulmonary inflammation. Hence, MCT-induced RHF does not help to distinguish whether the subsequent myocardial inflammation originates from the RHF per se or circulating inflammatory signals secreted by the injured lung.
In this article, a mechanical method involving pulmonary artery trunk banding (PAB) was used to provoke right-sided cardiac arrhythmogenesis. The PAB consists of performing a permanent suture of the pulmonary artery trunk for 3 weeks. Such an approach generates increased right-sided pressure overload. At D21 post-PAB, the suture results in hypertrophied, dilated, and inflamed RV and RA. The PAB-induced RHF is also accompanied by vulnerability to ventricular and atrial arrhythmias, including AF.

Right heart failure (RHF) is characterized by right-sided cardiac dilation and hypertrophy, leading to ventricular and atrial malfunction. Cardiopulmonary conditions associated with RHF are accompanied by an increased risk for cardiac arrhythmias. This article describes a standardized model of pulmonary artery banding-induced RHF associated with enhanced ventricular and atrial arrhythmogenesis.