**4. Radiofrequency ablation**

#### **4.1. Introduction of radiofrequency ablation**

Since Haissaguerre et al. demonstrated the efficacy of radiofrequency ablation for paroxysmal atrial fibrillation [20], radiofrequency has become the standard treatment for both catheterbased ablation and surgical ablation for cardiac arrhythmias. Chiappini et al. reported the efficacy of radiofrequency ablation in the patients who had chronic atrial fibrillation, and it was as effective as cut-and-sew Maze procedure [41, 42].

**4.3. Histopathological changes after radiofrequency ablation**

proarrhythmic activity found in the scar tissue [47].

**4.4. Transmurality of radiofrequency ablation**

ries to the valves.

permission from Medtronic, Inc.).

Heat propagation is based on both resistive and passive mechanisms. In the early phase of radiofrequency ablation, tissue is heated to 50–60°C resulting in coagulation and irreversible destruction of cell and collagen structures. Ablation of the peripheral part of the lesion results from passive heating with the same effect of irreversible damage. Both resistive and passive heating propagate in all directions so that the tissue lesion becomes similar in depth and width [41]. Once the transmurality is achieved with radiofrequency ablation, there is no

**Figure 5.** Illustration of the Cardioblate clamp, which utilizes bipolar radiofrequency energy source (Reproduced with

Histopathological Change Following Cox-Maze IV Procedure for Atrial Fibrillation

http://dx.doi.org/10.5772/intechopen.72786

69

Aupperle et al. reported the histological findings in experimental atrial ablation in sheep [48]. They reported that epicardial bipolar radiofrequency resulted in intensive endocardial necroses and severe sharply demarcated transmural myocardial necroses. Similarly, endocardial unipolar radiofrequency resulted in severe endocardial necroses as well as intense, transmural, and well demarcated myocardial necroses. Ba et al. also reported that radiofrequency resulted in myocyte necrosis in sheep, and radiofrequency was as effective as cryotherapy [49]. Gaynor et al. performed surgical ablation using bipolar radiofrequency energy source in pigs [50]. They reported histological assessment that showed all lesions created by bipolar radiofrequency were transmural and there were no stenosis of the coronary vessels or inju-

Although bipolar radiofrequency produces transmural linear lesions in the animals [51, 52], transmurality is not always achieved in human, as several papers reported [53, 54]. Deneke et al. reported that transmurality of the ablated lesions could only be found in 75% in human atria [55]. Kasirajan et al. reported the histopathological findings in three human patients who had autopsy after surgical ablation [53]. Their microscopic examination showed that (1) surgically ablated lesions showed not only transmural but also nontransmural lesions (**Figure 6**), (2) chronic ischemic and fibrotic changes existed in the myocardium of the patients who had long-standing persistent AF and mitral regurgitation, and (3) acute bi-directional electrical conduction block did not guarantee transmurality of ablation lesions. They assumed that the underlying disease process prevented the creation of transmural lesions. The wall thickness

However, lesions created by hyperthermia have a potential risk of tissue disruption that can result in perforation of surrounding tissue, pulmonary stenosis, and thromboembolic stroke [43, 44].

#### **4.2. Bipolar versus unipolar radiofrequency**

Bugge et al. compared the transmurality of ablated lesions in ovine hearts using irrigated bipolar and unipolar radiofrequency ablation [45]. They reported that bipolar radiofrequency was superior in creating transmurality, but both devices failed to produce consistent transmurality using the epicardial beating heart technique. Gonzalez-Suarez et al. also demonstrated that bipolar is more effective than unipolar in achieving transmurality in vitro [46]. However, the superiority of bipolar over unipolar in human has not been established.

AtriCure Inc. (Mason, OH) has provided bipolar radiofrequency ablation device, which has stainless steel shaft and jaws to maintain consistent tissue pressure and precise electrode alignment across the entire length of the jaws (**Figure 4**).

Medtonic Inc. (Minneapolis, MN) has provided Cardioblate system, which utilizes irrigated bipolar radiofrequency energy to ablate tissue transmurally (**Figure 5**).

**Figure 4.** Illustration of the bipolar radiofrequency clamp (Reproduced with permission from AtriCure, Inc.).

**Figure 5.** Illustration of the Cardioblate clamp, which utilizes bipolar radiofrequency energy source (Reproduced with permission from Medtronic, Inc.).

#### **4.3. Histopathological changes after radiofrequency ablation**

Heat propagation is based on both resistive and passive mechanisms. In the early phase of radiofrequency ablation, tissue is heated to 50–60°C resulting in coagulation and irreversible destruction of cell and collagen structures. Ablation of the peripheral part of the lesion results from passive heating with the same effect of irreversible damage. Both resistive and passive heating propagate in all directions so that the tissue lesion becomes similar in depth and width [41]. Once the transmurality is achieved with radiofrequency ablation, there is no proarrhythmic activity found in the scar tissue [47].

Aupperle et al. reported the histological findings in experimental atrial ablation in sheep [48]. They reported that epicardial bipolar radiofrequency resulted in intensive endocardial necroses and severe sharply demarcated transmural myocardial necroses. Similarly, endocardial unipolar radiofrequency resulted in severe endocardial necroses as well as intense, transmural, and well demarcated myocardial necroses. Ba et al. also reported that radiofrequency resulted in myocyte necrosis in sheep, and radiofrequency was as effective as cryotherapy [49]. Gaynor et al. performed surgical ablation using bipolar radiofrequency energy source in pigs [50]. They reported histological assessment that showed all lesions created by bipolar radiofrequency were transmural and there were no stenosis of the coronary vessels or injuries to the valves.

#### **4.4. Transmurality of radiofrequency ablation**

**Figure 4.** Illustration of the bipolar radiofrequency clamp (Reproduced with permission from AtriCure, Inc.).

cryoablation on a beating heart model in pigs [39]. Schill et al. reported that the latest cryoablation probe produced transmural lesions in 97% of the arrested heart in an ovine model [40]. However, the transmurality created by surgical cryoablation in the human tissue has not been

Since Haissaguerre et al. demonstrated the efficacy of radiofrequency ablation for paroxysmal atrial fibrillation [20], radiofrequency has become the standard treatment for both catheterbased ablation and surgical ablation for cardiac arrhythmias. Chiappini et al. reported the efficacy of radiofrequency ablation in the patients who had chronic atrial fibrillation, and it

However, lesions created by hyperthermia have a potential risk of tissue disruption that can result in perforation of surrounding tissue, pulmonary stenosis, and thromboembolic stroke

Bugge et al. compared the transmurality of ablated lesions in ovine hearts using irrigated bipolar and unipolar radiofrequency ablation [45]. They reported that bipolar radiofrequency was superior in creating transmurality, but both devices failed to produce consistent transmurality using the epicardial beating heart technique. Gonzalez-Suarez et al. also demonstrated that bipolar is more effective than unipolar in achieving transmurality in vitro [46]. However,

AtriCure Inc. (Mason, OH) has provided bipolar radiofrequency ablation device, which has stainless steel shaft and jaws to maintain consistent tissue pressure and precise electrode

Medtonic Inc. (Minneapolis, MN) has provided Cardioblate system, which utilizes irrigated

the superiority of bipolar over unipolar in human has not been established.

bipolar radiofrequency energy to ablate tissue transmurally (**Figure 5**).

well studied.

68 Cardiac Arrhythmias

[43, 44].

**4. Radiofrequency ablation**

**4.1. Introduction of radiofrequency ablation**

**4.2. Bipolar versus unipolar radiofrequency**

was as effective as cut-and-sew Maze procedure [41, 42].

alignment across the entire length of the jaws (**Figure 4**).

Although bipolar radiofrequency produces transmural linear lesions in the animals [51, 52], transmurality is not always achieved in human, as several papers reported [53, 54]. Deneke et al. reported that transmurality of the ablated lesions could only be found in 75% in human atria [55]. Kasirajan et al. reported the histopathological findings in three human patients who had autopsy after surgical ablation [53]. Their microscopic examination showed that (1) surgically ablated lesions showed not only transmural but also nontransmural lesions (**Figure 6**), (2) chronic ischemic and fibrotic changes existed in the myocardium of the patients who had long-standing persistent AF and mitral regurgitation, and (3) acute bi-directional electrical conduction block did not guarantee transmurality of ablation lesions. They assumed that the underlying disease process prevented the creation of transmural lesions. The wall thickness

**References**

athoracsur.2016.10.076

[1] Badhwar V, Rankin J, Damiano R Jr, Gillinov A, Bakaeen F, Edgerton J, Philpott J, McCarthy P, Bolling S, Roberts H, Thourani V, Suri R, Shemin R, Firestone S, Ad N. The Society of Thoracic Surgeons 2017 clinical practice guidelines for the surgical treatment of atrial fibrillation. The Annals of Thoracic Surgery. 2017;**103**:329-341. DOI: 10.1016/j.

Histopathological Change Following Cox-Maze IV Procedure for Atrial Fibrillation

http://dx.doi.org/10.5772/intechopen.72786

71

[2] Cox J, Boineau J, Schuessler R, Ferguson T Jr, Cain M, Lindsay B, Corr P, Kater K, Lappas D. Successful surgical treatment of atrial fibrillation. Review and clinical update. Journal of

[3] Cox J, Schuessler R, Lappas D, Boineau J. An 8 1/2-year clinical experience with surgery

[4] Millar R, Arcidi J Jr, Alison P. The maze III procedure for atrial fibrillation: Should the

[5] Mokadam N, McCarthy P, Gillinov A, Ryan W, Moon M, Mack M, Gaynor S, Prasad S, Wickline S, Bailey M, Damiano N, Ishii Y, Schuessler R, Damiano R Jr. A prospective multicenter trial of bipolar radiofrequency ablation for atrial fibrillation: Early results. The Annals of Thoracic Surgery. 2004;**78**:1665-1670. DOI: 10.1016/j.athoracsur.2004.05.066 [6] Gaynor S, Diodato M, Prasad S, Ishii Y, Schuessler R, Bailey M, Damiano N, Bloch J, Moon M, Damiano R Jr. A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation. The Journal of Thoracic and

[7] Damiano R Jr, Schwartz F, Bailey M, Maniar H, Munfakh N, Moon M, Schuessler R. The Cox maze IV procedure: Predictors of late recurrence. The Journal of Thoracic and

[8] Cheema F, Younus M, Pasha A, Cox J, Roberts H Jr. An effective modification to simplify the right atrial lesion set of the Cox-cryomaze. The Annals of Thoracic Surgery.

[9] Khargi K, Hutten B, Lemke B, Deneke T. Surgical treatment of atrial fibrillation; a systematic review. European Journal of Cardio-Thoracic Surgery. 2005;**27**:258-265. DOI:

[10] Ad N, Henry L, Hunt S. The concomitant cryosurgical Cox-maze procedure using Argon based cryoprobes: 12 month results. The Journal of Cardiovascular Surgery. 2011;**52**:593-599

[11] Gammie J, Laschinger J, Brown J, Poston R, Pierson R 3rd, Romar L, Schwartz K, Santos M, Griffith BA. Multi-institutional experience with the CryoMaze procedure. The Annals of

[12] Gaita F, Riccardi R, Caponi D, Shah D, Garberoglio L, Vivalda L, Dulio A, Chiecchio A, Manasse E, Gallotti R. Linear cryoablation of the left atrium versus pulmonary vein

Thoracic Surgery. 2005;**80**:876-880. DOI: 10.1016/j.athoracsur.2005.03.075

indications be expanded? The Annals of Thoracic Surgery. 2000;**70**:1580-1586

Cardiovascular Surgery. 2004;**128**:535-542. DOI: 10.1016/j.jtcvs.2004.02.044

Cardiovascular Surgery. 2011;**141**:113-121. DOI: 10.1016/j.jtcvs.2010.08.067

2013;**96**:330-332. DOI: 10.1016/j.athoracsur.2012.12.065

10.1016/j.ejcts.2004.11.003

the American Medical Association. 1991;**266**:1976-1980

for atrial fibrillation. Annals of Surgery. 1996;**224**:267-273

**Figure 6.** (**a**) Day 6 of surgical ablation. Extensive fibrosis in atrial tissue (blue) with necrotic myocardium (purple), and viable muscle (red). (Mason trichrome stain: magnification ×40.) (**b**) Day 18 of surgical ablation. Healing with coagulative necrosis and wavy bundles of collagen with few viable cells in between (hematoxylin and eosin: magnification ×100.).

of the atrium has been known to affect the transmurality [45]. Therefore, repeated radiofrequency ablation is recommended, especially in thick lesions [56, 57].

Ventosa-Fernandez et al. reported the histologic evidence of transmurality 4 years after bipolar radiofrequency ablation [58].
