This protocol follows the guidelines of local institution&#39;s human research ethics committee where applicable.
1. Assessment Prior to Placement
NOTE: Under current U.S. labeling, there are no formal contraindications listed. In the case of esophageal pathology, such as deformity, trauma, or recent ingestion of caustics or acidic material, caution is advised.
<ol>
	<li>Ensure that necessary equipment, such as the heat exchanger, the esophageal temperature management device, and water-based lubrication, is available.</li>
	<li>Attach the esophageal temperature management device to the heat exchanger via the device connectors, and power on the unit, placing it in manual mode. Ensure that the water is flowing through the esophageal temperature management device and confirm the absence of leaks.</li>
</ol>
2. Placement
<ol>
	<li>Determine the appropriate insertion depth for the esophageal temperature management device in similar manner to standard orogastric tube. Measure from the patient&#39;s lips to the earlobe and from the earlobe to xiphoid process and note this depth on the device (Figure 2).</li>
	<li>Use water-soluble lubricant to lubricate the esophageal temperature management device generously, at least 15 cm, and up to 25 cm of the distal end (Figure 3). 
	NOTE: Patients are typically under general inhalational anesthesia (for example, using sevoflurane), but may also be under intravenous anesthesia (for example, using propofol), or in some cases under conscious sedation (for example, using meperidine or midazolam).</li>
	<li>If possible, extend the patient&#39;s head to further facilitate insertion of the esophageal temperature management device using gentle pressure applied posteriorly and downwards, past the oropharynx and into the esophagus. Lifting the mandible anteriorly may assist passage of the device, as might a reduction of pressure in the ETT cuff if overinflated. Apply light pressure on the device as needed to reach the desired depth of placement. (Figure 4).</li>
	<li>Determine placement location by fluoroscopy to check if the tip of the device is below the diaphragm (Figure 5).</li>
	<li>Secure the water hoses and device to avoid accidental dislodgement; a common method is to place the connecting hose under the patient&#39;s left foam armrest.</li>
	<li>If stomach decompression is desired, connect the central lumen to low-intermittent suction using standard suction tubing.</li>
</ol>
3. Temperature Modulation &#8212; RF Ablation
<ol>
	<li>Ensure that the heat exchanger is set to manual mode and the appropriate water temperature is set. For example, on one typical heat exchanger, press the Temp Control button, then use the up/down arrows to select the target water temperature. Once the digital display shows the target temperature desired, initiate water flow by pressing the Manual Control button. A typical target is 4 &#176;C water temperature when performing radiofrequency ablation at the posterior left atrial wall.</li>
	<li>In order to anticipate the time needed for the heat exchanger to reduce temperature, use a water temperature setpoint of roughly 14 &#176;C for initial insertion in RF cases while awaiting transseptal puncture. After transseptal puncture, and approximately 15&#8211;20 min before application of RF energy to the posterior atrial wall, change the water temperature setpoint to 4 &#176;C (in manual mode). 
	NOTE: For additional anti-inflammatory effects of cooling which may reduce gastroparesis or chest pain post-procedure, operators may maintain the water temperature setpoint at 4 &#176;C for 20 min after the completion of posterior wall ablation, at which point the machine can be turned off.</li>
</ol>
4. Temperature Modulation &#8212; Cryoablation
<ol>
	<li>For cryoablation, use a water temperature setpoint of 42 &#176;C (typical).</li>
	<li>Set this water temperature shortly after placement (placing while cold is generally easier due to increased device stiffness), and continue throughout the case, providing additional patient warming to counter the systemic cooling effect of the cryoablation.</li>
</ol>
5. Patient Temperature Monitoring
NOTE: Because the temperature in the esophagus is modulated by the presence of an esophageal heat transfer device, a different location is necessary for patient temperature measurement. Options for patient temperature measurement include nasopharyngeal thermometer (ensure that the depth is less than 10 cm), Foley temperature sensor, rectal temperature sensor, tympanic membrane thermometer, or forehead thermometer (including zero-flux thermometry).
<ol>
	<li>To maintain patient temperature when using esophageal cooling, use supplemental warming modalities, such as warming blankets or head covers if needed. During esophageal warming when performing cryoablation, the patient temperature will usually stay in a normothermic range.</li>
</ol>
6. Troubleshooting
<ol>
	<li>Ensure that no blockage of water flow occurs, and that the water paddle wheel, if present, is continuously spinning, or the low-flow alarm is not activated.</li>
	<li>Blockage of water flow in the system will cause the paddle wheel to stop spinning and an occlusion alert on the external heat exchanger Stop treatment and determine the location and cause of obstruction. If necessary, remove and replace the esophageal temperature management device.</li>
	<li>Confirm water flow at correct temperature by checking setpoint and touching device to ensure adequate pressure (device will be firm) and appropriate temperature.</li>
</ol>
7. Removal of Device
<ol>
	<li>Press the appropriate button to pause water flow; this may be labelled &#34;Monitor&#34; or &#34;Temp Set&#34;, but may vary by model.</li>
	<li>If present, close clamps on the hose set and/or device tubing, and withdraw the device from the patient by gently pulling anteriorly in a similar manner to standard orogastric tube removal.</li>
	<li>Power down the heat exchange unit via the power switch prior to unplugging from wall power.</li>
	<li>Disconnect the water hose connectors from the device and dispose as per institutional policy (typically via contaminated waste container).</li>
</ol>

<ol>
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EK is an equity owner of Attune Medical, manufacturer of esophageal heat transfer technology. MG, PS, CT, JG, and BC serve as Principal Investigators for studies of esophageal cooling with funding to their hospital institutions, but receive no direct corporate compensation. MM has provided consulting services for Attune Medical. All other authors declare no conflicts of interest with this work.

Modification of the placement procedure may be necessary by crimping the water outflow tube, increasing the stiffness of the heat exchange device during placement. The identification of which connecting tube is water outflow can be performed by crimping either tube and examining to see which causes the device to stiffen, and which causes the device to soften. Crimping the inlet tube will decrease water inlet flow and soften the device, crimping the outlet will increase water backpressure and stiffen it.
Limitations of this method of esophageal temperature modulation to counteract thermal injury from left atrial ablation include the inherent heat-transfer limitation of any technology. Although whole-body temperature modulation can be achieved with esophageal heat exchange, there is still the potential to overcome this heat transfer capacity if sufficient energy is utilized in ablation. As such, changes from standard ablation parameters are not recommended, and usual ablation technique should be maintained. In general, the device is utilized in patients that are endotracheally intubated; however, a number of sites utilize this protocol in patients under conscious sedation without difficulty22. Finally, there remains some uncertainty as to the factors necessary for fistula formation, and aspects beyond energy exchange may be involved.
The use of direct esophageal temperature modulation to prevent esophageal injury during atrial ablation has been used in various forms over the last several years. The most common use has been in cooling during RF ablation, using either balloon devices or direct instillation of cold fluid8,9,10,11,12,13,14,15. More recent use has focused on warming to counteract cryothermal injury during cryoablation23,24,25,26. Use of a dedicated esophageal heat transfer device such as described in this protocol offers the advantage of targeting specific temperatures in the esophagus while avoiding the significant risks and logistical workload of direct instillation of free liquid into the GI tract.
Future applications of this method include the leverage of the known protean effects of patient temperature modulation, in particular temperature reduction27,28. Given the well-described protective effects of hypothermia on injured neurons, an additional application may involve the reduction of post-operative cognitive dysfunction29,30,31,32. Recent data in the burn literature reviewing 2,495 patients highlight the importance of cooling thermal injury in reducing burn depth, grafting, and operative requirements, noting that the mechanisms involve more than just dissipation of heat, but also the alteration of cellular behavior through decreasing release of lactate and histamine, stabilizing thromboxane and prostaglandin levels, and inhibiting kallikrein activity33. If similar mechanisms of action are involved in the esophagus, additional benefits to surrounding structures might be anticipated. Preliminary findings and anecdotal data suggest that the anti-inflammatory effects of cooling may reduce infarct size after certain subsets of myocardial injury, renal dysfunction after transplantation, the occurrence of post-operative pericarditis, and the rate of post-procedure gastroparesis34,35,36,37.
Critical steps include ensuring (a) proper placement of the heat transfer device (b) proper water temperature setpoint, and (c) continual water circulation through the heat transfer device. Proper placement of the device is readily confirmed with fluoroscopy, with particular attention towards the epigastric region near where the tip of the heat exchange device is expected to terminate. Water temperature is easily adjusted on the heat exchanger console, keeping in mind that up to 7&#8211;10 min may be needed for the circulating water to attain the setpoint temperature from the starting temperature. Continual water circulation is necessary for the device to properly transfer heat. Water circulation can be confirmed by visualization of the spinning water-flow paddle wheel present on some heat exchanger models. On heat exchanger models that lack a water-flow paddle wheel, an alarm will trigger when flow is obstructed. A potential cause of water flow obstruction is improper placement of the heat exchange device (if placed too deep, causing bending/kinking of the tube in the distal stomach, or in rarer cases, if allowed to coil up and bend in the oropharynx or proximal esophagus during placement). Troubleshooting in this case involves a simple visualization under fluoroscopy to determine placement level and adjusting as needed.

Left atrial ablation to perform pulmonary vein isolation (PVI) is increasingly utilized for the treatment of atrial fibrillation1. The attainment of PVI can be achieved with radiofrequency (RF) energy to burn atrial tissue or with direct application of cryothermal energy; however, collateral damage to surrounding structures remains a risk with either method, with esophageal injury being one of the most serious2,3,4. The most extreme esophageal injury, atrioesophageal fistula (AEF), remains challenging to prevent and diagnose, and carries a very high mortality5,6.
A number of techniques have been utilized to reduce the risk of AEF, including reducing power applied to vulnerable regions, monitoring luminal esophageal temperature (LET), deviating the esophagus during ablation, and cooling or warming the esophagus7. Directly countering the thermal energy delivered to the esophagus, primarily by cooling against the RF heating, has been used in a variety of formats8,9,10,11,12,13,14,15,16. An advantage to cooling during RF ablation or warming during cryoablation is that a preventive approach to injury is taken, in contrast to temperature monitoring, which involves a reactive approach (stopping ablation when temperature rises). The reactive approach, although often used, may be of limited efficacy17, with a recent review noting that currently available discrete sensor probes, whether single or multiple, do not appear to significantly reduce injury rates7. Cooling or warming also avoids the need for procedural pauses and device manipulation required with esophageal deviation techniques, which have been reported to cause esophageal trauma and involve difficulties in use18,19. A recent meta-analysis of esophageal cooling for the purpose of protecting the esophagus during RF ablation found a 61% reduction in high-grade lesion formation in a total of 494 patients20. A recent randomized-controlled trial found a statistically significant 83% reduction in endoscopically identified lesions when using a dedicated cooling device compared to standard LET monitoring21.
The goal of this protocol is to demonstrate the use of esophageal cooling or warming during left atrial radiofrequency or cryo-ablation using an esophageal temperature management device (Figure 1).

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Cincinnati SubZero Blanketrol II</td>
			<td>Gentherm</td>
			<td>n/a</td>
			<td>Compatible heat-exchanger with the ECD02</td>
		</tr>
		<tr>
			<td>Cincinnati SubZero Blanketrol III</td>
			<td>Gentherm</td>
			<td>n/a</td>
			<td>Compatible heat-exchanger with the ECD02</td>
		</tr>
		<tr>
			<td>EnsoETM</td>
			<td>Attune Medical</td>
			<td>ECD01</td>
			<td>Device compatible with Gaymar/Stryker Medi-Therm III and Stryker Altrix Precision Temperature Management System</td>
		</tr>
		<tr>
			<td>EnsoETM</td>
			<td>Attune Medical</td>
			<td>ECD02</td>
			<td>Device compatible with Cincinnati SubZero Blanketrol II and Cincinnati SubZero Blanketrol III</td>
		</tr>
		<tr>
			<td>Gaymar/Stryker Medi-Therm III</td>
			<td>Stryker</td>
			<td>n/a</td>
			<td>Compatible heat-exchanger with the ECD01</td>
		</tr>
		<tr>
			<td>Stryker Altrix Precision Temperature Management System</td>
			<td>Stryker</td>
			<td>n/a</td>
			<td>Compatible heat-exchanger with the ECD01</td>
		</tr>
		<tr>
			<td>Water-soluble lubricant</td>
			<td>Various</td>
			<td>n/a</td>
			<td>Standard water-soluble lubricant used to ease insertion of tubes, catheters, and digits</td>
		</tr>
	</tbody>
</table>

cooling or warming the esophagus to reduce esophageal injury during left atrial ablation in the treatment of atrial fibrillation

Ablation of the left atrium using either radiofrequency (RF) or cryothermal energy is an effective treatment for atrial fibrillation (AF) and is the most frequent type of cardiac ablation procedure performed. Although generally safe, collateral injury to surrounding structures, particularly the esophagus, remains a concern. Cooling or warming the esophagus to counteract the heat from RF ablation, or the cold from cryoablation, is a method that is used to reduce thermal esophageal injury, and there are increasing data to support this approach. This protocol describes the use of a commercially available esophageal temperature management device to cool or warm the esophagus to reduce esophageal injury during left atrial ablation. The temperature management device is powered by standard water-blanket heat exchangers, and is shaped like a standard orogastric tube placed for gastric suctioning and decompression. Water circulates through the device in a closed-loop circuit, transferring heat across the silicone walls of the device, through the esophageal wall. Placement of the device is analogous to the placement of a typical orogastric tube, and temperature is adjusted via the external heat-exchanger console.

A large number of patients have been studied using esophageal cooling via direct instillation of cold liquid into the esophagus during RF ablation (for example, by injecting a 20 mL bolus of ice-cold saline via orogastric tube into the upper esophagus when the LET increased by 0.5 &#176;C above baseline). The findings of a meta-analysis of existing studies using this technique is summarized in Figure 620.
Data from a randomized-controlled clinical trial evaluating a dedicated cooling device were recently presented, and are summarized in Table 121. Ablation parameters for the control and treatment arms, respectively, were as follows: RF duration, 14.1 versus 14.5 min; average force, 19.1 versus 17.8 g, maximum RF power, 33.9 versus 34.1 W, and average ablation index, 394 versus 384, with all differences non-significant. All patients had PVI with additional lesion sets when required. At the time of presentation, no difference in recurrence rate of atrial fibrillation at 6 months was found between the two groups (4/27 in control group, 3/17 in treatment group).
Example RF ablation result: 
A 59 year-old female with a past medical history of hyperlipidemia, diabetes, and recurrent paroxysmal atrial fibrillation presented for an RF ablation procedure. An esophageal heat transfer device circulating 14 &#176;C water was placed in the esophagus, with the setpoint reduced to 4 &#176;C after transseptal puncture, approximately 8 min before the start of ablation. The ablation was performed using a three-dimensional mapping system and a 3.5 mm irrigated ablation catheter for segmental pulmonary vein isolation. A setting of 30 W on the posterior aspect of the pulmonary veins, with up to 40 W on the anterior was used, with duration of up to 20 s. PVI as well as linear posterior wall isolation (Box lesion) was performed. Patient temperature was measured via nasopharyngeal probe placed less than 10 cm into the nares, with patient start temperature of 36.4 &#176;C, and end temperature of 36.1 &#176;C. Approximately 20 min after completion of ablation on the posterior wall, the esophageal heat transfer device setpoint was raised to 40 &#176;C to provide patient warming while access sheaths were removed and vascular closure was completed. Endoscopy performed the following day as part of a research protocol demonstrated no esophageal lesions.
Example cryoablation result: 
A 68 year-old male with past medical history of hypertension and increasing episodes of paroxysmal atrial fibrillation presented for cryoballoon ablation. An esophageal heat transfer device circulating room temperature (22 &#176;C) water was placed in the esophagus. Once placed, the setpoint temperature was raised to 42 &#176;C. Ablations were performed with a cryoballoon system. Initial patient core temperature was measured at 36.3 &#176;C via Foley catheter temperature sensor. Temperatures in the esophagus were measured with a single-sensor temperature probe (routine use of a temperature probe device co-located with the heat transfer device is not recommended, as the optimal benefit is obtained with full contact between heat transfer device and esophageal mucosa, but is described here to show the effect on preventing excessive temperature decreases). Beginning with cryoablation at the left superior pulmonary vein, the initial esophageal temperature measured was 38.6 &#176;C and reached a nadir of 36.4 &#176;C during the cryoablation. Nadir balloon temperature was -51 &#176;C. Block was obtained in under 30 s, with a single 180 second freeze performed. At the left inferior pulmonary vein, the beginning temperature was 38.5 &#176;C and reached a low of 38.0 &#176;C after two cycles of treatment (a bonus freeze of 120 s was performed because of delay in obtaining block on initial freeze until 70 s in). Nadir balloon temperature was -48 &#176;C. In the right superior pulmonary vein, initial esophageal temperature was 38.4 &#176;C, remained unchanged through two cycles, and ended at 38.5 &#176;C. Nadir balloon temperature was -47 &#176;C. Finally, in the right inferior pulmonary vein, initial esophageal temperature was 38.9 &#176;C and reached a nadir of 38.8 &#176;C throughout two cycles of treatment. Nadir balloon temperature was -39 &#176;C. Patient temperature at the end of the procedure was 36.0 &#176;C, and all cryoballoon treatments maintained esophageal temperature well above common stopping thresholds (15 &#176;C to 25 &#176;C).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/60733/60733fig1.jpg" /> 
Figure 1: Image of esophageal temperature management device in-situ (with permission from Attune Medical). <a href="https://www.jove.com/files/ftp_upload/60733/60733fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/60733/60733fig2a.jpg" /> 
Figure 2: Measurement of the appropriate insertion depth for the esophageal temperature management device. This is performed by extending the device from the patient&#39;s lips to the earlobe and then from the earlobe to the tip of the xiphoid process, and then marking the insertion depth on the device. <a href="https://www.jove.com/files/ftp_upload/60733/60733fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/60733/60733fig3a.jpg" /> 
Figure 3: Lubrication of the device. Lubrication of the esophageal temperature management device, generously applying approximately lubricant to 25 cm of the distal end with water-soluble lubricant. <a href="https://www.jove.com/files/ftp_upload/60733/60733fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/60733/60733fig4a.jpg" /> 
Figure 4: Advancement of the device with light pressure, until the required length of tube has been inserted. <a href="https://www.jove.com/files/ftp_upload/60733/60733fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/60733/60733fig5.jpg" /> 
Figure 5: Fluoroscopic image demonstrating the tip of the device below the diaphragm. <a href="https://www.jove.com/files/ftp_upload/60733/60733fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/60733/60733fig6a.jpg" /> 
Figure 6: Summary of data from meta-analysis of studies on esophageal cooling utilizing direct liquid instillation. <a href="https://www.jove.com/files/ftp_upload/60733/60733fig6alarge.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Table 1" src="/files/ftp_upload/60733/60733table1.jpg" /> 
Table 1: Summary of primary outcome of randomized-controlled study of dedicated esophageal cooling device.

Watch this Scientific Journal Video about Cooling or Warming the Esophagus to Reduce Esophageal Injury During Left Atrial Ablation in the Treatment of Atrial Fibrillation at JoVE.com

Cooling or Warming the Esophagus to Reduce Esophageal Injury During Left Atrial Ablation in the Treatment of Atrial Fibrillation

The goal of this protocol is to describe the use of esophageal temperature modulation to counteract esophageal thermal injury from left atrial ablation for the treatment of atrial fibrillation.

Ablation of the left atrium using either radiofrequency (RF) or cryothermal energy is an effective treatment for atrial fibrillation (AF) and is the most ...

cooling-or-warming-esophagus-to-reduce-esophageal-injury-during-left

Research

JoVE Journal

Medicine

9.2K Views.  St. David's South Austin Medical Center. The goal of this protocol is to describe the use of esophageal temperature modulation to counteract esophageal thermal injury from left atrial ablation for the treatment of atrial fibrillation.

Video: Cooling or Warming the Esophagus to Reduce Esophageal Injury During Left Atrial Ablation in the Treatment of Atrial Fibrillation

The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting an estimated 6 million people in the United States 1. Since AF affects primarily elderly people, its prevalence increases parallel with age. As such, it is expected that 15.9 million Americans will be affected by the year 2050 2. Ischemic stroke occurs in 5% of non-anticoagulated AF patients each year. Current treatments for AF include rate control, rhythm control and prevention of stroke 3.
The American College of Cardiology, American Heart Association, and European Society of Cardiology currently recommended rate control as the first course of therapy for AF 3. Rate control is achieved by administration of pharmacological agents, such as &beta;-blockers, that lower the heart rate until it reaches a less symptomatic state 3. Rhythm control aims to return the heart to its normal sinus rhythm and is typically achieved through administration of antiarrhythmic drugs such as amiodarone, electrical cardioversion or ablation therapy. Rhythm control methods, however, have not been demonstrated to be superior to rate-control methods 4-6. In fact, certain antiarrhythmic drugs have been shown to be associated with higher hospitalization rates, serious adverse effects 3, or even increases in mortality in patients with structural heart defects 7. Thus, treatment with antiarrhythmics is more often used when rate-control drugs are ineffective or contraindicated. Rate-control and antiarrhythmic agents relieve the symptoms of AF, including palpitations, shortness of breath, and fatigue 8, but don't reliably prevent thromboembolic events 6.
Treatment with the anticoagulant drug warfarin significantly reduces the rate of stroke or embolism 9,10. However, because of problems associated with its use, fewer than 50% of patients are treated with it. The therapeutic dose is affected by drug, dietary, and metabolic interactions, and thus requires detailed monitoring. In addition, warfarin has the potential to cause severe, sometimes lethal, bleeding 2. As an alternative, aspirin is commonly prescribed. While aspirin is typically well tolerated, it is far less effective at preventing stroke 10. Other alternatives to warfarin, such as dabigatran 11 or rivaroxaban 12 demonstrate non-inferiority to warfarin with respect to thromboembolic events (in fact, dabigatran given as a high dose of 150 mg twice a day has shown superiority). While these drugs have the advantage of eliminating dietary concerns and eliminating the need for regular blood monitoring, major bleeding and associated complications, while somewhat less so than with warfarin, remain an issue 13-15.
Since 90% of AF-associated strokes result from emboli that arise from the left atrial appendage (LAA) 2, one alternative approach to warfarin therapy has been to exclude the LAA using an implanted device to trap blood clots before they exit. Here, we demonstrate a procedure for implanting the WATCHMAN Left Atrial Appendage Closure Device. A transseptal cannula is inserted through the femoral vein, and under fluoroscopic guidance, inter-atrial septum is crossed. Once access to the left atrium has been achieved, a guidewire is placed in the upper pulmonary vein and the WATCHMAN Access Sheath and dilator are advanced over the wire into the left atrium. The guidewire is removed, and the access sheath is carefully advanced into the distal portion of the LAA over a pigtail catheter. The WATCHMAN Delivery System is prepped, inserted into the access sheath, and slowly advanced. The WATCHMAN device is then deployed into the LAA. The device release criteria are confirmed via fluoroscopy and transesophageal echocardiography (TEE) and the device is released.

The accompanying video describes a procedure for percutaneous placement of the WATCHMAN Left Atrial Appendage (LAA) Device. The WATCHMAN is a nitinol device designed to be permanently implanted at, or slightly distal to, the opening of the left atrial appendage (LAA) to trap blood clots before they exit the LAA, preventing thromboembolic stroke.

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting an estimated 6 million people in the United States 1. Since AF affects primarily ...

Catheter Ablation in Combination With Left Atrial Appendage Closure for Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting millions of individuals worldwide 1-3. The rapid, irregular, and disordered electrical activity in the atria gives rise to palpitations, fatigue, dyspnea, chest pain and dizziness with or without syncope 4, 5. Patients with AF have a five-fold higher risk of stroke 6.
Oral anticoagulation (OAC) with warfarin is commonly used for stroke prevention in patients with AF and has been shown to reduce the risk of stroke by 64% 7. Warfarin therapy has several major disadvantages, however, including bleeding, non-tolerance, interactions with other medications and foods, non-compliance and a narrow therapeutic range 8-11. These issues, together with poor appreciation of the risk-benefit ratio, unawareness of guidelines, or absence of an OAC monitoring outpatient clinic may explain why only 30-60% of patients with AF are prescribed this drug 8.
The problems associated with warfarin, combined with the limited efficacy and/or serious side effects associated with other medications used for AF 12,13, highlight the need for effective non-pharmacological approaches to treatment. One such approach is catheter ablation (CA), a procedure in which a radiofrequency electrical current is applied to regions of the heart to create small ablation lesions that electrically isolate potential AF triggers 4. CA is a well-established treatment for AF symptoms 14, 15, that may also decrease the risk of stroke. Recent data showed a significant decrease in the relative risk of stroke and transient ischemic attack events among patients who underwent ablation compared with those undergoing antiarrhythmic drug therapy 16.
Since the left atrial appendage (LAA) is the source of thrombi in more than 90% of patients with non-valvular atrial fibrillation 17, another approach to stroke prevention is to physically block clots from exiting the LAA. One method for occluding the LAA is via percutaneous placement of the WATCHMAN LAA closure device. The WATCHMAN device resembles a small parachute. It consists of a nitinol frame covered by fabric polyethyl terephthalate that prevents emboli, but not blood, from exiting during the healing process. Fixation anchors around the perimeter secure the device in the LAA (Figure 1). To date, the WATCHMAN is the only implanted percutaneous device for which a randomized clinical trial has been reported. In this study, implantation of the WATCHMAN was found to be at least as effective as warfarin in preventing stroke (all-causes) and death (all-causes) 18. This device received the Conformit&eacute; Europ&eacute;enne (CE) mark for use in the European Union for warfarin eligible patients and in those who have a contraindication to anticoagulation therapy 19.
Given the proven effectiveness of CA to alleviate AF symptoms and the promising data with regard to reduction of thromboembolic events with both CA and WATCHMAN implantation, combining the two procedures is hoped to further reduce the incidence of stroke in high-risk patients while simultaneously relieving symptoms. The combined procedure may eventually enable patients to undergo implantation of the WATCHMAN device without subsequent warfarin treatment, since the CA procedure itself reduces thromboembolic events. This would present an avenue of treatment previously unavailable to patients ineligible for warfarin treatment because of recurrent bleeding 20 or other warfarin-associated problems.
The combined procedure is performed under general anesthesia with biplane fluoroscopy and TEE guidance. Catheter ablation is followed by implantation of the WATCHMAN LAA closure device. Data from a non-randomized trial with 10 patients demonstrates that this procedure can be safely performed in patients with a CHADS2 score of greater than 1 21. Further studies to examine the effectiveness of the combined procedure in reducing symptoms from AF and associated stroke are therefore warranted.

Catheter ablation is combined with placement of the WATCHMAN Left Atrial Appendage Closure Device to prevent ischemic stroke in a patient with non-valvular atrial fibrillation.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting millions of individuals worldwide 1-3. The rapid, irregular, and ...

Robotic Ablation of Atrial Fibrillation

Background: Pulmonary vein isolation (PVI) is an established treatment for atrial fibrillation (AF). During PVI an electrical conduction block between pulmonary vein (PV) and left atrium (LA) is created. This conduction block prevents AF, which is triggered by irregular electric activity originating from the PV. However, transmural atrial lesions are required which can be challenging. Re-conduction and AF recurrence occur in 20 - 40% of the cases. Robotic catheter systems aim to improve catheter steerability. Here, a procedure with a new remote catheter system (RCS), is presented. Objective of this article is to show feasibility of robotic AF ablation with a novel system. Materials and Methods: After interatrial trans-septal puncture is performed using a long sheath and needle under fluoroscopic guidance. The needle is removed and a guide wire is placed in the left superior PV. Then an ablation catheter is positioned in the LA, using the sheath and wire as guide to the LA. LA angiography is performed over the sheath. A circular mapping catheter is positioned via the long sheath into the LA and a three-dimensional (3-D) anatomical reconstruction of the LA is performed. The handle of the ablation catheter is positioned in the robotic arm of the Amigo system and the ablation procedure begins. During the ablation procedure, the operator manipulates the ablation catheter via the robotic arm with the use of a remote control. The ablation is performed by creating point-by-point lesions around the left and right PV ostia. Contact force is measured at the catheter tip to provide feedback of catheter-tissue contact. Conduction block is confirmed by recording the PV potentials on the circular mapping catheter and by pacing maneuvers. The operator stays out of the radiationfield during ablation. Conclusion: The novel catheter system allows ablation with high stability on low operator fluoroscopy exposure.

Pulmonary vein isolation (PVI) with an ablation catheter is a curative treatment for atrial fibrillation (AF). Robotic catheter systems aim to improve catheter steerability. Here, a procedure with a new robotic catheter system is presented. The goal of the procedure is electrical block between pulmonary vein and left atrium.

Background: Pulmonary vein isolation (PVI) is an established treatment for atrial fibrillation (AF). During PVI an electrical conduction block between ...

Left Atrial Stenosis Induced Pulmonary Venous Arterialization and Group 2 Pulmonary Hypertension in Rat

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of group 2 PH, due to mitral stenosis (MS), to facilitate the investigation of disease mechanisms and potential therapeutic strategies. We present a novel rat model of pulmonary venous congestion-induced pulmonary venous arterialization and group 2 PH caused by left atrial stenosis (LAS). LAS is achieved by constricting the left atrium using a half-closed titanium clip. After the LAS surgery, a rat model with a transmitral inflow velocity greater than or equal to 2.0 m/s on echocardiography gradually develops pulmonary venous arterialization and group 2 PH over an 8- to 10-week period. In this protocol, we provide the step-by-step procedure of how to perform the LAS surgery. The presented LAS rat model mimics MS in humans and is useful for studying the underlying molecular mechanism of pulmonary venous arterialization and for the preclinical evaluation of therapies for group 2 PH.

Left atrial stenosis (LAS) is a novel surgical technique used for studying group 2 pulmonary hypertension (PH) and mechanisms underlying pulmonary venous arterialization. Here, we present a protocol to constrict the left atrium using a titanium clip to cause pulmonary venous arterialization and moderate PH in a rat.

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of ...

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 ...

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.

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. ...

Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation

Atrial fibrillation (AF) is the most common form of arrhythmia. Atrial remodeling is considered the most critical mechanism for the presence and development of atrial fibrillation. Also, atrial remodeling can lead to the enlargement and dysfunction of the left atrium (LA), resulting in thrombosis and heart failure. Functional changes in left atrial strain and strain rate occur before structural alterations and are closely associated with structural remodeling and left atrial fibrosis. These parameters are sensitive biomarkers for atrial function. Cardiac magnetic resonance feature tracking (CMR-FT) is a novel, non-invasive, post-processing technique that can evaluate left atrial strain and strain rate. The CMR-FT was utilized in this investigation to assess the bilateral atrium strain rate in individuals with paroxysmal AF. Modifications in each segmental strain were evaluated using segmental analysis. The CMR-FT is recommended for non-invasive evaluations in the clinical assessment of atrial strain among existing strain imaging techniques. Further, it is a flexible parameter measurement with good reproducibility, high soft-tissue resolution, and post-processing based on standard cine balanced steady-state free precision (bSSFP) long-axis images without requiring a new sequence acquisition.

The atrial function is associated with the strain and strain rate. The cardiac magnetic resonance feature tracking (CMR-FT) technique was used in this study to quantify left and right atrial global and segmental longitudinal strain and strain rate in individuals with paroxysmal atrial fibrillation.

Atrial fibrillation (AF) is the most common form of arrhythmia. Atrial remodeling is considered the most critical mechanism for the presence and ...

Reduced Procedure Time and Variability with Active Esophageal Cooling During Radiofrequency Ablation for Atrial Fibrillation

Various methods are utilized during radiofrequency (RF) pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF) to protect the esophagus from inadvertent thermal injury. Active esophageal cooling is increasingly being used over traditional luminal esophageal temperature (LET) monitoring, and each approach may influence procedure times and the variability around those times. The objective of this study is to measure the effects on procedure time and variability in procedure time of two different esophageal protection strategies utilizing advanced informatics techniques to facilitate data extraction. Trained clinical informaticists first performed a contextual inquiry in the catheterization laboratory to determine laboratory workflows and observe the documentation of procedural data within the electronic health record (EHR). These EHR data structures were then identified in the electronic health record reporting database, facilitating data extraction from the EHR. A manual chart review using a REDCap database created for the study was then performed to identify additional data elements, including the type of esophageal protection used. Procedure duration was then compared using summary statistics and standard measures of dispersion.&#160;A total of 164 patients underwent radiofrequency PVI over the study timeframe; 63 patients (38%) were treated with LET monitoring, and 101 patients (62%) were treated with active esophageal cooling. The mean procedure time was 176 min (SD of 52 min) in the LET monitoring group compared to 156 min (SD of 40 min) in the esophageal cooling group (P = 0.012). Thus, active esophageal cooling during PVI is associated with reduced procedure time and reduced variation in procedure time when compared to traditional LET monitoring.

This study utilized advanced informatics techniques to compare procedure duration in patients undergoing radiofrequency atrial ablation treated with active esophageal cooling to those treated with traditional luminal esophageal temperature monitoring. Contextual inquiry, workflow analysis, and data mapping were utilized. The findings demonstrated reduced procedure time and variability with active cooling.

Various methods are utilized during radiofrequency (RF) pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF) to protect the ...

ICE-Based 3D Remodeling for the Left Atrium and Pulmonary Vein

Three-Dimensional Modeling of the Left Atrium and Pulmonary Veins with a Precise Intracardiac Echocardiography Approach

Intracardiac echocardiography (ICE) is a novel tool for estimating cardiac anatomy during pulmonary vein isolation procedures, particularly the left atrium (LA) anatomy and pulmonary vein structures. ICE is widely used to establish a three-dimensional (3D) left atrial structural model during ablation procedures. However, it is unclear whether using ICE in a precise 3D modeling method can provide a more accurate left atrial 3D model and the transseptal approach. This study proposes a protocol to model the left atrium and pulmonary veins with ICE and fast anatomical mapping (FAM) catheter remodeling. It evaluates the accuracy of the models produced using the two methods through observer scoring. We included 50 patients who underwent ICE-based 3D remodeling and 45 who underwent FAM 3D remodeling based on pulmonary vein isolation procedures. The pulmonary vein antrum remodeling is estimated by comparing the antrum area acquired by remodeling and left atrial computed tomography angiography (CTA). The observer scores for the modeling in the ICE and FAM groups were 3.40 &#177; 0.81 and 3.02 &#177; 0.72 (P &#60; 0.05), respectively. The pulmonary vein antrum area obtained using the ICE- and FAM-based methods showed a correlation with the area acquired by left atrium CT. However, the 95% confidence interval bias was narrower in ICE-acquired models than in FAM-acquired models (-238 cm2 to 323 cm2 Vs. -363 cm2 to 386 cm2, respectively) using Bland-Altman analysis. Therefore, precise ICE possesses high accuracy in estimating the left atrial structure, becoming a promising approach for future cardiac structure estimation.

Author Spotlight: Advancements in Intracardiac Echocardiography for Atrial Anatomy Assessment 

Accurate intracardiac echocardiography (ICE) shows significant accuracy in estimating the left atrial structure, a prospective and promising cardiac structure estimation method. Here we propose a protocol for three-dimensional modeling of the left atrium and pulmonary veins with ICE and fast anatomical mapping (FAM) catheter remodeling.

Intracardiac echocardiography (ICE) is a novel tool for estimating cardiac anatomy during pulmonary vein isolation procedures, particularly the left ...

Revealing Murine Pulmonary Veins Myocardial Architecture

Microdissection and Immunofluorescence Staining of Myocardial Sleeves in Murine Pulmonary Veins

Pulmonary veins (PVs) are the major source of ectopic beats in atrial arrhythmias and play a crucial role in the development and progression of atrial fibrillation (AF). PVs contain myocardial sleeves (MS) composed of cardiomyocytes. MS are implicated in the initiation and maintenance of AF, as they preserve similarities to the cardiac working myocardium, including the ability to generate ectopic electrical impulses. Rodents are widely used and may represent excellent animal models to study the pulmonary vein myocardium since cardiomyocytes are widely present all over the vessel wall. However, precise microdissection and preparation of murine PVs is challenging due to the small organ size and intricate anatomy.
We demonstrate a microscopy-guided microdissection protocol for isolating the murine left atrium (LA) together with the PVs. Immunofluorescence staining using cardiac Troponin-T (cTNT) and connexin 43 (Cx43) antibodies is performed to visualize the LA and PVs in full length. Imaging at 10x and 40x magnification provides a comprehensive view of the PV structure as well as detailed insights into the myocardial architecture, particularly highlighting the presence of connexin 43 within the MS.

Author Spotlight: Developing a Translational Model for Atrial Fibrillation Research Across Species 

This protocol demonstrates microscopy-guided isolation and immunofluorescence staining of murine pulmonary veins. We prepare tissue samples containing the left atrium, pulmonary veins, and the corresponding lungs and stain them for cardiac Troponin T and Connexin 43.

Pulmonary veins (PVs) are the major source of ectopic beats in atrial arrhythmias and play a crucial role in the development and progression of atrial ...