Ablation technology for the surgical treatment of atrial fibrillation

One hundred percent utilization of a modified CryoMaze III procedure for atrial fibrillation with mitral surgery

OBJECTIVES

Concomitant atrial fibrillation often goes untreated because of surgeon concerns regarding lesion set complexity and pump times. We describe a new cryoablation procedure to address this.

METHODS

From June 2013 to March 2021, a modified CryoMaze III procedure was used using 3 left atrial ± 3 right atrial cryo-applications creating the key lesions of the Cox Maze III procedure. Since 2018, 3-minute cryo-lesions were used for the left atrial box lesion for total cryoablation times of 8 minutes for the left atrium ± 6 minutes for the right atrium. By using propensity matching, patients undergoing mitral valve surgery with no atrial fibrillation history were compared with CryoMaze III-treated patients.

RESULTS

A total of 100% of the 277 patients with atrial fibrillation requiring mitral valve surgery ± other procedures received the modified CryoMaze III procedure. After propensity score matching (n = 161 each group), the modified CryoMaze III group had mean crossclamp and bypass times 10.5 and 13.4 minutes longer than the control group, respectively. There were no significant differences in 30-day mortality, morbidity, pacemaker use, renal dysfunction, or late survival between groups, but there were less postoperative strokes in the CryoMaze III group. Freedom from atrial fibrillation off antiarrhythmics was 77% (mean follow-up of 3.0 ± 2.1 years). At 12 months, freedom from atrial fibrillation off antiarrhythmics was 90% for the 3-minute ablation group. Late survival was similar to age- and sex-matched Centers for Disease Control and Prevention controls.

CONCLUSIONS

The modified CryoMaze III technique is efficient, safe, and effective. Education of the surgical community regarding the late benefits of ablation and the simplicity of this new technique should improve adoption of the Class I Guidelines to treat concomitant atrial fibrillation.

Performance of an Irrigated Bipolar Radiofrequency Ablation Clamp on Explanted Human Hearts

BACKGROUND

Bipolar radiofrequency (RF) clamps are commonly used during surgical ablation for atrial fibrillation (AF). This study examined the efficacy of an irrigated bipolar RF clamp to create transmural lesions in an ex vivo human heart model.

METHODS

Ten donor hearts, turned down for transplantation, were explanted and arrested with cold cardioplegia. The ablations of the Cox Maze IV procedure were performed using the Cardioblate LP (Medtronic, Inc) irrigated bipolar RF clamp. In the first 5 hearts, each lesion was created with a single application of RF, whereas in the remaining 5 hearts, each lesion was created with a double application of RF without unclamping. Each lesion was cross-sectioned and stained with 2,3,5-triphenyl-tetrazolium chloride to assess ablation depth and transmurality.

RESULTS

A total of 100 lesions were analyzed. In the single-ablation group, 222 of 260 sections (85%) and 37 of 50 lesions (74%) were transmural. The efficacy improved significantly in the double-ablation group, in which 348 of 359 sections (97%, P < .001) and 46 of 50 lesions (92%, P = .017) were transmural. Overall, in nontransmural lesions, the epicardial fat thickness was significantly greater (1.69 ± 0.70 mm vs 0.45 ±0.10 mm, P < .001) than the transmural lesions.

CONCLUSIONS

A single ablation on human atrial tissue with an irrigated bipolar RF clamp was insufficient to reliably create transmural lesions, but a double ablation significantly increased the lesion and section transmurality. Nontransmural lesions were associated with significantly thicker layers of epicardial fat, which likely decreased tissue energy delivery due to the higher resistance of fat to current flow.

Hybrid surgical epicardial cryoablation for ventricular tachycardia in the electrophysiology laboratory: a case report

Background

Scar-related ventricular tachycardia (VT) is a challenging medical condition, with catheter ablation providing a valuable treatment option. Whilst most VTs can be ablated endocardially, epicardial ablation is often required in patients with non-ischaemic cardiomyopathy. The percutaneous subxiphoid technique has become instrumental for epicardial access. However, it is not feasible in up to 28% of cases for multiple reasons.

Case summary

A 47-year-old patient was managed at our centre for VT storm and recurrent implantable cardioverter defibrillator shocks for monomorphic VT despite maximum drug therapy. No scar was noted during endocardial mapping, with confirmation of the localized epicardial scar on cardiac magnetic resonance imaging (CMR). Following failed percutaneous epicardial access, a successful hybrid surgical epicardial VT cryoablation via median sternotomy was performed in the electrophysiology (EP) laboratory utilizing data from CMR, prior endocardial ablation, and conventional EP mapping. The patient has remained arrhythmia-free for 30 months post-ablation without antiarrhythmic therapy.

Discussion

This case describes a practical multidisciplinary approach to managing a challenging clinical problem. Whilst the described technique is not entirely novel, this is the first case report that describes the practicalities and demonstrates the safety and feasibility of hybrid epicardial cryoablation via median sternotomy performed in the cardiac EP laboratory for the sole treatment of VT.

Efficacy of a Novel Bipolar Radiofrequency Clamp: An Acute Porcine Model

OBJECTIVE

Expert consensus guidelines recommend surgical ablation (SA) for patients with symptomatic atrial fibrillation (AF), but less than half of patients with AF undergoing cardiac procedures receive concomitant SA. Complete isolation of the left atrial posterior wall (LAPW) has been shown to be the most critical part of the Cox maze procedure. The purpose of this study was to investigate the performance of a novel radiofrequency (RF) bipolar device, EnCompass™ (AtriCure, Inc., Mason, OH, USA), designed to isolate the LAPW in a single application.

METHODS

Five adult pigs underwent SA in a beating heart model. After a single ablation, the heart was arrested, explanted, and stained with triphenyl-tetrazolium-chloride for histological assessment. Each lesion was sectioned, and the ablation depth, muscle, and fat thickness were determined. The lesion width, energy delivery, and ablation times were compared with those from a reference RF clamp (Synergy™, AtriCure).

RESULTS

Transmurality was documented in 100% of lesions (5 of 5) and cross sections (160 of 160). Electrical isolation was documented in every instance. There was no evidence of clot, charring, or pulmonary vein stenosis. Compared with the reference clamp, the lesions created by the EnCompass™ clamp were 1.5 times wider on average. The average energy delivered was 5 times higher over a duration that was 4.5 times longer due to the increased volume of tissue ablated.

CONCLUSIONS

The EnCompass™ clamp reproducibly created transmural isolation of the LAPW with a single application. This may allow for simplification of the SA strategy and increased adoption of AF treatment during concomitant surgery.

Study on the effect of different blood flow velocities of pulmonary vein on endocardial microwave ablation of atrial fibrillation

OBJECTIVE

To cure atrial fibrillation, the maximum ablation depth (⩾ 50∘C) should exceed the myocardial thickness to achieve the effect of transmural ablation. The blood flow of pulmonary vein in the endocardium can cause the change in the myocardial temperature distribution. Therefore, the study investigated the effect of different pulmonary vein blood flow velocities on the endocardial microwave ablation.

METHODS

The finite element model of the endocardial microwave ablation of pulmonary vein was simulated by electromagnetic thermal flow coupling. The ablation power was 30 W and the ablation time was within 30 s. The blood flow in the coupling of fluid mechanics equation and heat transfer equation results in the heat damage. Furthermore, the cause of the different lesion dimensions is the blood flow velocity. The flow velocities were set as 0, 0.02, 0.05, 0.07, 0.12, 0.16, 0.20, 0.25 and 0.30 m/s.

RESULTS

When the flow velocities were 0, 0.02, 0.05, 0.07, 0.12, 0.16, 0.20, 0.25 and 0.30 m/s, the maximum ablation depth were 6.0, 5.56, 5.16, 5.12, 5.04, 5.01, 4.98, 4.96 and 4.94 mm, respectively; the maximum ablation width were 12.52, 9.63, 9.23, 9.16, 9.07, 9.05, 8.94, 8.91, 8.90 mm, respectively; the maximum ablation length were 12.00, 11.61, 8.98, 8.59, 8.37, 8.23, 8.16, 8.06 and 8.04 mm respectively. To achieve transmural ablation, the time was 3, 3, 3, 3, 3, 4, 4, 4, 4 s, respectively when the myocardial thickness was 2 mm; the time was 7, 8, 8, 8, 9, 9, 9, 9, 9 s, respectively when 3 mm; the time was 15, 16, 18, 19, 19, 20, 20, 20, 20 s, respectively when 4 mm.

CONCLUSIONS

When the velocity increases from 0 m/s to 3 m/s, the microwave lesion depth decreases by 1.06 mm. To achieve transmural ablation, when the myocardial thickness is 2 mm, 3 and 4 s should be taken when the velocity is 0-0.12 and 0.120.30 m/s, respectively; when the myocardial thickness is 3 mm, 7, 8 and 9 s should be taken when 0, 0-0.07 and 0.07-0.30 m/s respectively; when the myocardial thickness is 4 mm, 15, 16, 18, 19, 20 s should be taken when 0, 0-0.02, 0.02-0.05, 0.05-0.12, 0.12 m/s-0.30 m/s.

Biparietal bidirectional bipolar radiofrequency in hybrid cardiac ablation: an in vitro evaluation

 

OBJECTIVES

The aim of this study was to evaluate the lesion size and depth of radiofrequency (RF) ablation in a simultaneous biparietal bidirectional bipolar (SBB) approach, compared to a simultaneous and staged unipolar and uniparietal bipolar setup [simultaneous uniparietal bipolar (SiUB) and staged uniparietal bipolar (StUB), respectively].

METHODS

Fresh left atrial porcine tissue was mounted into the ABLA-BOX simulator. Different ablation approaches were tested: (i) SBB: a concept consisting of SBB endo-epicardial ablation, (ii) SiUB: simultaneous epicardial uniparietal bipolar and endocardial unipolar ablation and (iii) StUB: staged epicardial uniparietal bipolar and endocardial unipolar ablation. In the StUB setup, a 1-h interval between the epi-endo ablation was respected.

RESULTS

Transmural lesions were present in 90% of the bipolar biparietal ablations, yet no full transmurality was observed in the simultaneous nor in the staged unipolar with uniparietal bipolar ablation group. In SBB, the area and volume of the ablation lesions were smaller (523.33 mm2/mm and 52.33 mm3/mm, respectively) than in SiUB (588.17 mm2/mm and 58.81 mm3/mm, respectively) and StUB (583.76 mm2/mm and 58.37 mm3/mm, P = 0.044). Also, in SBB, the overall, epicardial and endocardial maximum diameters of the lesions (1.59, 1.57 and 1.52 mm; respectively) were smaller than in SiUB (2.38, 2.26 and 2.33 mm; respectively) and in StUB (2.36, 2.28 and 2.14 mm; respectively, all P < 0.001).

CONCLUSIONS

Although bipolar biparietal bidirectional RF ablation results in smaller lesions than uniparietal bipolar and unipolar ablation, their capacity to penetrate the tissue is much higher. Moreover, in uniparietal RF applications, the energy spreads in the superficial layers of the tissue but fails to penetrate. Therefore, the degree of transmurality is much higher when using such a 'truly bipolar' ablation approach.

New Biparietal Bipolar Catheter Prototype for Hybrid Atrial Fibrillation Ablation

Objective

To evaluate the size and depth of linear lesions by in vitro testing with a custom-made radio frequency biparietal bipolar ablation catheter in a single-stage setting.

Methods

A custom-made catheter was created to generate linear lesions around the left atrium and pulmonary veins of an ex vivo pig. Two frames were made, 1 epicardial and 1 endocardial. A continuous copper braid electrode and an alignment system consisting of 2 parallel rows of neodymium magnets were embedded in a flexible plastic support. After 24 hours of formalin conservation, samples of the left atrium of a freshly slaughtered pig were sliced in a cryotome, thus obtaining a sequence of 100-µm thick layers extending from the endocardial to the epicardial side. After being digitized through a scanner, these layers were evaluated using morphometric computer software. For each slice, we evaluated the maximum length of the lesions, the maximum epicardial length, the maximum endocardial length, the total area of the lesion, and the total volume.

Results

Forty transmural lesions from 40 specimens were obtained. The results were the following (the number in parenthesis is the interquartile range in mm): lesion maximum length (L_MAX) was 7.297 mm (0.006), epicardial maximum length (L_EPI) was 7.291 mm (0.014), and endocardial maximum length was 7.291 mm (0.018). The total area and total volume were 1018.50 ± 36.51 mm² and 101.85 ± 3.65 mm³, respectively.

Conclusions

Our prototype showed very promising results. The next step will be to enhance the design for clinical application.

Comparison between biparietal bipolar and uniparietal bipolar radio frequency ablation techniques in a simultaneous procedural setting

Purpose

To make an in vitro evaluation of the lesion size and depth produced in two different sets of radio frequency energy bipolar delivery: simultaneous biparietal bipolar (SBB) and simultaneous uniparietal bipolar (SUB).

Methods

Two separate prototypes have been built for our purpose: one to be used in SBB mode and the other to be used SUB mode. Forty left atrium samples were taken from the hearts of freshly slaughtered pigs. They were ablated into a simulator ABLABOX, where blood flow, temperature, and contact force were controlled. After being sliced into a cryotome, the samples were digitalized by a flatbed scanner, and the images were analyzed by a computer morphometric software.

Results

Transmural lesions were achieved in 18/20 samples (90%) in SBB, while SUB showed transmurality in 9/20 samples (45%). Overall maximum diameter (D_MAX) resulted larger in SUB than in SBB (2.43 ± 0.30 mm, 1.62 ± 0.14 mm, respectively; p < 0.05): Moreover, maximum epicardial and endocardial diameters (D_EPI and D_ENDO, respectively) were wider in SUB group than SBB group (2.28 ± 0.30 mm, 2.26 ± 0.40 and 1.60 ± 0.14 mm, 1.59 ± 0.15 mm, respectively; p < 0.05). We observed the same tendency in lesion depth: The total area and volume (A_TOT and V_TOT) were broader in SUB group than in SBB one (581.01 ± 65.38 mm/mm², 58.10 ± 6.53 mm/mm³ and 521.97 ± 73.05 mm/mm², 52.19 ± 7.30 mm/mm³. respectively; p < 0.05).

Conclusions

In contrast with the smaller lesion sizes, the biparietal bipolar group showed a higher transmurality rate. These findings may suggest a better drive of the energy flow when compared with SUB lesions.

Bipolar Radiofrequency Ablation on Explanted Human Hearts: How to Ensure Transmural Lesions

BACKGROUND

Bipolar radiofrequency (RF) clamps have been shown to be capable of reproducibly creating transmural lesions with a single ablation in animal models. Unfortunately in clinical experience the bipolar clamps have not been as effective and often require multiple ablations to create conduction block. This study created a new experimental model using fresh, cardioplegically arrested human hearts turned down for transplant to evaluate the performance of a nonirrigated bipolar RF clamp.

METHODS

Nine human hearts turned down for transplant were harvested, and the Cox-Maze IV lesion set was performed with a nonirrigated bipolar RF clamp. In the first 7 hearts a single ablation was performed for each lesion. In the last 2 hearts a set of 2 successive ablations without unclamping were performed. The heart tissue was stained with 2,3,5-triphenyl-tetrazolium chloride. Each ablation lesion was cross-sectioned to assess lesion depth and transmurality.

RESULTS

A single ablation with the bipolar RF clamp resulted in 89% (469/529) of the histologic sections and 65% (42/65) of the lesions being transmural. Of the nontransmural sections, 92% occurred in areas with epicardial fat. Performing 2 successive ablations without unclamping resulted in 100% of the cross-sections (201/201) and lesions (25/25) being transmural.

CONCLUSIONS

A single ablation failed to create a transmural lesion 35% of the time, and this was associated with the presence of epicardial fat. Two successive ablations without unclamping resulted in 100% lesion transmurality using the bipolar RF clamp.

Catheter ablation is preferred over surgery for persistent atrial fibrillation

There are important limitations that can hinder outcomes of surgical ablation in nonparoxysmal patients with atrial fibrillation (AF), which is the typical AF population undergoing concomitant cardiac surgery for valve or ischemic heart disease. Incomplete lesions with recovered conduction or gaps as well as arrhythmias originating from areas not targeted by surgical ablation are commonly seen at the time of recurrence. Therefore, while it might be reasonable to perform AF surgery in this cohort, it is important to know these limitations and establish adequate postoperative rhythm monitoring to detect recurrences, which can be effectively addressed by catheter ablation.

Energy Sources for the Surgical Treatment of Atrial Fibrillation

The surgical treatment of atrial fibrillation has evolved over the past 2 decades due to the advent of ablation technology, and the introduction of less invasive surgical approaches. Current devices produce ablation lines that aim to replace the incisions of traditional surgical ablation strategies, such as the Cox-Maze procedure. This has helped to simplify and shorten surgical ablation procedures and has allowed for the development of minimally invasive surgical techniques. This review discusses surgical ablation energy sources and devices, providing background on device characteristics, mechanism of tissue injury, and success in creating transmural lesions.

The Same is Not the Same: Device Effect during Bipolar Radiofrequency Ablation of Atrial Fibrillation

BACKGROUND

Different ablation devices deliver the same type of energy but use individual control mechanisms to estimate efficacy. We compared patient outcome after the application of radiofrequency ablation systems, using temperature- or resistance-control in paroxysmal and persistent atrial fibrillation (AF).

METHODS

This is an unselected all-comers study. Patients underwent standardized left atrial (paroxysmal atrial fibrillation, [PAF] n = 31) or biatrial ablation (persistent atrial fibrillation [persAF] n = 61) with bipolar RF from October 2010 to June 2013. Patients with left atrial dilatation (up to 57 mm), reduced left ventricular (LV) function, and elderly were included. We used resistance-controlled (RC) or temperature-controlled (TC) devices. We amputated atrial appendices and checked intraoperatively for completeness of pulmonary vein exit block. All patients received implantable loop recorders. Follow-up interval was every 6 months. Antiarrhythmic medical treatment endured up to month 6.

RESULTS

We reached 100% freedom from atrial fibrillation (FAF) in PAF. In perAF 19% of the RC but 82% of the TC patients reached FAF (12 months; p < 0.05). TC patients exhibited higher creatine kinase-muscle/brain (CK-MB) peak values. In persAF, CK-MB-levels correlated to FAF. No and no mortality (30 days) was evident. Twelve-month mortality did not correlate to AF type, AF duration, LV dimension, or function and age. Prolonged need of oral anticoagulants was 90.1% (RC) and 4.5% (TC).

CONCLUSION

In patients with persAF undergoing RF ablation, TC reached higher FAF than RC. Medical devices are not "the same" regarding effectiveness even if used according to manufacturer's instructions. Thus, putative application of "the same" energy is not always "the same" efficacy.

The Role of Collaboration Between Electrophysiologists and Surgeons in the Management of Complex Arrhythmia Patients

Although the need for surgery in patients with arrhythmias has declined in the past several decades due to the emergence of catheter ablation, there is still room for collaboration between electrophysiologists and surgeons, mainly when managing patients with atrial fibrillation, ventricular tachycardia, and cardiac implantable electronic devices.

Contact force and ablation assessment of surgical bipolar radiofrequency clamps in the treatment of atrial fibrillation

OBJECTIVES

Atrial fibrillation is treated surgically by creating conduction block lesions. Radiofrequency (RF) lesions have reduced efficacy compared to 'cut-and-sew'. Catheter ablation studies demonstrate a relationship between lesion depth and contact force. We hypothesized that contact force and lesion depth are dependent on design of the bipolar surgical RF clamps.

METHODS

Hinged and parallel jaw style RF clamps were studied. Muscle samples were clamped with pressure-sensitive film at increasing tissue thicknesses. Films were analysed determining clamp pressure profiles. A sheep model was utilized for ablation testing using each clamp style until the device indicated transmurality. Separate muscle areas had 1, 2 or 3 burns applied. The muscle was excised, sectioned every 1 cm and stained for lesion depth and fat thickness analysis.

RESULTS

Pressure profiling comparing the proximal and distal segments of each clamp style demonstrated only one statistically significant difference in the parallel clamp; the hinged clamp had statistically significant differences (P ≤ 0.03) for all tissue thicknesses. There was no evidence for differences in the proximal lesion depth of both clamps (P = 0.13) but deeper distally in the parallel clamp (10.17 mm vs 8.02 mm, P = 0.003). The logistic regression analysis demonstrated increased odds of transmurality with parallel clamps at 1, 2 or 3 burns (P = 0.03, P = 0.003 and P = 0.002). Every 1 mm increase in overlying fat decreased likelihood of transmurality by 11% (P < 0.05).

CONCLUSIONS

The parallel and hinged clamps have different pressure profiles with higher likelihood of transmurality using the parallel clamp. Fat reduces the ability of RF to deliver a transmural lesion. These findings have implications for optimal surgical RF ablation technique.

Valve surgery in combination with cryoablation in the treatment of atrial fibrillation

Objective:

To investigate the effectiveness and safety of valve surgery in combination with cryoablation in the treatment of atrial fibrillation.

Methods:

Fifty patients who needed to undergo valve surgery because of heart valve disease and sixty-five patients who needed to undergo valve surgery in combination with cryoablation were selected as the research subjects. The perioperative technical characteristics, postoperative curative effect and complications were compared between the two different treatment modalities in our hospital between October 2013 and November 2015.

Results:

No significant differences were observed between the two groups in valve surgery mode, valve type and postoperative length of hospital stay (P>0.05), but the duration of extracorporeal bypass and aorta occlusion of the observation group was longer than that of the control group (P<0.05). The 3-month, 6-month and one-year atrial fibrillation cardioversion rates of patients in the observation group were superior to those of the control group, and the differences were notable (P<0.05). The improvement of left atrial diameter of the observation group was also superior to that of the control group (P<0.05). The incidence of postoperative complications of the two groups had no significant difference (P>0.05).

Conclusion:

Valve surgery in combination with cryoablation has favorable short-term clinical effect in the treatment of heart valve disease in combination with atrial fibrillation, which is worth promotion.

Termination of Atrial Fibrillation With Epicardial Cooling in the Oblique Sinus

OBJECTIVES

This study aimed to determine if epicardial cooling could repeatedly terminate induced atrial fibrillation (AF) in a canine heart.

BACKGROUND

Rapid termination of AF could control symptoms and prevent atrial remodeling; however, defibrillation by internal electrical cardioversion is not tolerable to most patients. Cooling of the epicardium slows atrial conduction and may provide a less painful method to quickly terminate AF.

METHODS

AF was induced with atrial myocardial epinephrine injections and rapid atrial pacing in an open-chest canine. Attempts at termination were performed with a small metal device that was either cooled to 5°C or kept at body temperature (control module). The device was placed on the epicardial surface in the oblique sinus. The time from device contact to termination of AF was recorded.

RESULTS

In 5 different canine studies, there were 57 attempts at AF termination with either a 5°C module (34 attempts) or a control module (23 attempts). The median (interquartile range [IQR]) time to AF termination was 24 s (IQR: 15 to 35 s) for the 5°C therapy and 100 s (IQR: 47 to 240 s) for the body temperature treatments (p < 0.001). In the control group, there were 8 AF episodes that continued up to 4 min. Subsequent application of the 5°C cooling module terminated AF in all cases.

CONCLUSIONS

Epicardial cooling in the oblique sinus is effective for repeated termination of AF in a canine heart. If reproduced in human studies, epicardial cooling with an implantable device may provide a method for management of patients with AF.

The Role of Echocardiography in Determining the Method of Ablation for the Treatment of Paroxysmal Atrial Fibrillation: A Literature Review

Atrial fibrillation is the most common cardiac arrhythmia, affecting approximately 1 out of every 250 people. It is associated with thrombus formation in the left atrium, decreased cardiac output, and deterioration of the myocardium. There are multiple treatments available for paroxysmal atrial fibrillation. This literature review will assess the benefits, risks, and complications associated with radiofrequency ablation and cryoablation, which utilize heat and freezing mechanisms, respectively. The review will also assess the role of echocardiography in determining which treatment, if any, is appropriate for atrial fibrillation.

Pulmonary Hypertension due to Radiofrequency Catheter Ablation (RFCA) for Atrial Fibrillation: The Lungs, the Atrium or the Ventricle?

Atrial fibrillation is the most common heart rhythm disorder in United States, characterised by rapid and irregular beating of both the atria resulting in the similar ventricular response. While rate and rhythm control using pharmacological regimens remain the primary management strategies in these patients, radiofrequency catheter ablation (RFCA) is rapidly rising as an alternative modality of treatment. Increase in the incidence of RFCA has shed light on complications associated with this procedure. Pulmonary hypertension (PH) is one of the long-term complications that has been observed postcatheter ablation. There have been multiple mechanisms which have been proposed to explain these elevated pulmonary pressures. These include the involvement of the lungs due to pulmonary vein stenosis, pulmonary vein occlusion and, rarely, pulmonary embolism. Radiofrequency catheter ablation can also lead to scarring of the atrium which can cause left atrial diastolic dysfunction leading to elevated pulmonary pressures. Recently, it was also proposed that elevated pulmonary pressure was related to the unmasking of left ventricular diastolic dysfunction occurring after this procedure. In this article, we review all the mechanisms that are associated with the development of pulmonary hypertension in patients undergoing RCFA for atrial fibrillation and the approach to diagnosis and management of such patients.

Minimally Invasive Atrial Fibrillation Surgery: Hybrid Approach

Atrial fibrillation is a challenging pathologic process. There continues to be a great need for the development of a reproducible, durable cure when medical management has failed. An effective, minimally invasive, sternal-sparing intervention without the need for cardiopulmonary bypass is a promising treatment approach. In this article, we describe a hybrid technique being refined at our center that combines a thoracoscopic epicardial surgical approach with an endocardial catheter-based procedure. We also discuss our results and review the literature describing this unique treatment approach.

The ABLATE Trial: Safety and Efficacy of Cox Maze-IV Using a Bipolar Radiofrequency Ablation System

BACKGROUND

The Cox Maze-IV procedure (CMP-IV) has replaced the Cox Maze-III procedure as the most common approach for the surgical treatment of atrial fibrillation (AF). The Food and Drug Administration-regulated AtriCure Bipolar Radiofrequency Ablation of Permanent Atrial Fibrillation (ABLATE) trial sought to demonstrate the safety and efficacy of the CMP-IV performed with the Synergy ablation system (AtriCure, Inc, Cincinnati, OH).

METHODS

Fifty-five patients (aged 70.5 ± 9.3 years), 92.7% of whom had nonparoxysmal AF, underwent CMP-IV to terminate AF during a concomitant cardiac surgical procedure. Lesions were created using the AtriCure Synergy bipolar radiofrequency ablation system. All patients were seen for follow-up visits after 30 days, 3 months, and 6 months, with 24-hour Holter monitoring at 6 months. Late evaluation was performed by 48-hour Holter monitoring at an average of 21 months.

RESULTS

The primary efficacy endpoint, absence of AF (30 seconds or less) at 6-month follow-up off antiarrhythmic medications (Heart Rhythm Society definition), indicated 76% (38 of 50) were AF free (95% confidence interval: 62.6% to 85.7%). The primary safety endpoint, the rate of major adverse events within 30 days, was 9.1% (5 of 55; 95% confidence interval: 3.9% to 19.6%), with 3.6% mortality (2 of 55). Secondary efficacy endpoints included being AF free with antiarrhythmic drugs (6 months, 84%; 21 months, 75%), successful pulmonary vein isolation (100%), and AF burden at 6 and 21 months. The results, together with those for the secondary safety endpoint (6-month major adverse events), demonstrated that the Synergy system performs comparably to the cut-and-sew Cox Maze-III procedure.

CONCLUSIONS

The CMP-IV using the AtriCure Synergy system was safe and effective for cardiac surgical patients who had persistent and longstanding persistent AF.

Atrial fibrillation therapy now and in the future: drugs, biologicals, and ablation

Atrial fibrillation (AF) is a complex disease with multiple inter-relating causes culminating in rapid, seemingly disorganized atrial activation. Therapy targeting AF is rapidly changing and improving. The purpose of this review is to summarize current state-of-the-art diagnostic and therapeutic modalities for treatment of AF. The review focuses on reviewing treatment as it relates to the pathophysiological basis of disease and reviews preclinical and clinical evidence for potential new diagnostic and therapeutic modalities, including imaging, biomarkers, pharmacological therapy, and ablative strategies for AF. Current ablation and drug therapy approaches to treating AF are largely based on treating the arrhythmia once the substrate occurs and is more effective in paroxysmal AF rather than persistent or permanent AF. However, there is much research aimed at prevention strategies, targeting AF substrate, so-called upstream therapy. Improved diagnostics, using imaging, genetics, and biomarkers, are needed to better identify subtypes of AF based on underlying substrate/mechanism to allow more directed therapeutic approaches. In addition, novel antiarrhythmics with more atrial specific effects may reduce limiting proarrhythmic side effects. Advances in ablation therapy are aimed at improving technology to reduce procedure time and in mechanism-targeted approaches.