MMCTS
(June 18, 2009). doi:10.1510/mmcts.2007.003061
Copyright © 2009 European Association for Cardio-thoracic Surgery
Procedure
Off-pump epicardial high intensity focused ultrasound ablation of atrial fibrillation in patients undergoing structural heart repair1
Mark Groh*
Asheville Cardiovascular and Thoracic Surgeons, Mission Hospitals, Asheville, NC 28803, USA
* Corresponding author: Tel.: +1-828-2581121; fax: +1-828-2526114. mgroh{at}avlcvsurgeons.com
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Summary
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There are a number of different devices and approaches to the management of atrial fibrillation (AF) coexisting in patients undergoing structural heart repair. Based on the widespread applicability and safety of an epicardial approach, the uniqueness of the energy source and the lesion set obtainable, we began a systematic program in 2005 utilizing high intensity focused ultrasound (HIFU). Our approach has been standardized in the operative and postoperative phases. Epicardial HIFU ablation performed concomitantly in patients undergoing other cardiac surgery has been performed over 300 times in the last 3 years at our institution. Over 90% of patients with AF complicating structural heart disease are offered an ablation in our practice. Freedom from AF has remained at over 80% in patients treated, with no additional risk to the patient resulting from the ablation procedure.
Key Words: Atrial fibrillation • Clinical outcomes • Surgical treatment
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Introduction
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Atrial fibrillation (AF) is frequently seen to coexist in patients with other structural heart disease requiring operative intervention. In patients with structural heart disease, AF is observed in 20–40% of patients with mitral valve disease, 10–15% of patients with disorders of the aortic valve and in 5–10% of patients undergoing coronary revascularization [1]. There is also evidence of improved long-term outcomes in patients who maintain sinus rhythm after corrective cardiac procedures [2, 3, 4]. These data would support the concomitant treatment of AF at the time of operative intervention for other cardiac problems. Despite the significant decrease in adverse cardiac events and mortality seen in patients who maintain SR after cardiac surgery, nearly two-thirds of patients undergoing cardiac procedures with AF do not undergo concomitant ablation [1]. Indeed, data indicate that most patients with higher risk profiles for adverse outcomes with cardiac surgery are frequently not ablated [1]. Data from congestive heart failure (SOLVD trial, 1991) registries show that the presence of AF significantly increases the rate of deterioration of LV function. Many high-risk patients with congestive heart failure and AF may be the patients who would most significantly benefit from maintenance of SR after surgery but are not being ablated [1]. Increased cardiac ischemia and cardiopulmonary bypass times as well as the need to enter cardiac chambers to perform the ablation that would not otherwise require opening with the structural heart repair are all potential reasons for failure to treat AF in the concomitant setting [2]. The epicardial approach affords the ability to treat AF in patients undergoing cardiac surgery with no additional risk, acceptable efficacy and minimal disruption of the operative procedure.
The high intensity focused ultrasound (HIFU) technology is unique [5]. Ultrasonic energy over 1000 times as intense as diagnostic ultrasound is focused and delivered to different depths of the left atrial wall utilizing a cinch device composed of piezo-ceramic transducers enclosed in saline irrigated cells that are placed around the left atrial wall and deliver the energy towards the left atrial cavity, alleviating the risk of collateral damage. The device produces a wide area of ablation, 1.5 cm in width, on the antrum of the left atrium through the use of an automated algorithm that generally takes 9–12 min. Once in position and the algorithm initiated, the surgeon can continue with the cannulation sequence, maintaining the flow of the operation. A hand wand, consisting of two transducers, is routinely employed to perform the mitral isthmus line, also from the epicardium.
The mitral isthmus line anatomically is an extension of the left inferior pulmonary vein connecting the previous box lesion created with the cinch to the coronary sinus. At this section of the left atrium the coronary sinus represents the projection of the mitral annulus itself and the circumflex artery is as a rule the lowest element of the vascular pedicle, far below the inferior margin of the coronary sinus and stays away from the lower edge of the hand-held ‘wand’.
Diagram of the HIFU transducer
The delivery of energy with HIFU is significantly different with other heating technologies. Radiofrequency and other thermal conductive energies heat tissue by direct application of heat on the tissue. HIFU transmits energy and as the energy interacts with the tissue the heat is generated (Photo 1).
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Photo 1 Diagram of the HIFU algorithm with three consecutive stages of ultrasonic energy delivery originating from the transducer.
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Surgical technique
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The procedure is performed off-pump and may be performed via sternotomy or right anterior thoracotomy. The lesion set for the ablation is ‘en bloc’ pulmonary vein encircling with the cinch device and the mitral line with the hand-held wand (Photo 2).
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Photo 2 Representation of the lesion as seen from the epicardium and associating a circumferential line encircling the pulmonary veins, associated to a short linear lesion extending over the mitral isthmus from the original line to the left lower pulmonary vein orifice.
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The procedure is demonstrated on a patient in permanent AF for 4 years undergoing concomitant CABG (Videos 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12).
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Video 1 The pericardium is opened and suspended. Entry into the transverse sinus is obtained by dissecting underneath the superior vena cava (SVC). The space should be wide enough to accommodate two fingers. Once the SVC is dissected, adhesions that extend from the right pulmonary artery to the dome of the left atrium are divided. This tissue must be divided to allow the cinch to lie flat and in contact with the dome of the left atrium as it emerges under the SVC.
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Video 2 The oblique sinus is opened between the right lower pulmonary vein and the IVC, again to accommodate two fingers.
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Video 3 Sizer is introduced into the transverse sinus underneath the SVC. It passes behind the great vessels and emerges from the sinus anterior to the pulmonary artery.
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Video 4 The apex of the heart is lifted with the left hand and the sizer is placed in the posterior pericardium. The tip of the sizer is seen in the oblique sinus. The tip of the sizer is then grasped with a clamp and pulled forward.
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Video 5 The left atrium is sized by holding the clamp in the left hand and tightening the sizer around the atrium with the right hand. The tightening happens on the surface of the left atrium to accurately determine the appropriate size of the cinch expressed as the number of corresponding transducers. The tip of the sizer is aligned with the appropriate mark visible on the sizer as the device envelopes the left atrium. Should the tip of the sizer come to rest between two demarcations with tightening, the smaller number is chosen.
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Video 6 The cinch corresponding to the correct size is carefully de-aired. It is then connected to the sizer and introduced into the transverse sinus. As the device is passed through the transverse sinus it will ‘autorotate’ clockwise once in the free pericardial space lateral to the pulmonary artery. At this time, the sizer/introducer may now be pulled to bring the leading portion of the cinch into vision under the inferior vena cava.
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Video 7 Color-coded cinch sutures are then secured with a right angle clamp. The sutures are secured with Rumel tourniquets and the introducer is released from the cinch by cutting prolene sutures.
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Video 8 Demonstrates the screen of the ACS showing power delivery during the procedure. During this time the surgeon will place venous cannulation sutures and cannulate the aorta.
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Video 9 After the ablation sequence is complete, the Rumel tourniquets are released and the device is removed. The ablation line is inspected.
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Video 10 The hand wand for performance of the mitral line is prepared and de-aired.
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Video 11 ‘Lima’ pericardial reflection suture is placed to lift the cardiac apex. Patient is placed in steep Trendelenbourg position and the mitral line is created by placing the wand in the line of the left inferior pulmonary vein, connecting from the previous ablation line to and across the coronary sinus.
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Video 12 The wand is stabilized between two fingers on the left hand during the 85 s ablation. The mitral line is inspected.
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Postoperative management
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Postoperative management of the AF patient is an integral part of the procedure. Diligence in follow-up, accompanied by standardized approaches to antiarrhythmic drug management, cardioversion and anticoagulation have allowed us to optimize outcomes for our patients. Only through comprehensive follow-up can real gains be made in assessing the efficacy of lesion sets and ablative technologies. Late follow-up, after 18 months, consists of yearly ECG, Holter monitor and physical examination. Early follow-up is more intense with clinic visits at 2 weeks, 2, 3, 6 and 12 months. ECG analysis is performed at each clinic visit as well as 24 h Holter monitor at 3, 6, 12 and 18 months. Cardioversion, if required, is scheduled around the 12 weeks' visit. Antiarrhythmics are generally continued for 10 weeks postoperatively in patients in SR. In patients requiring cardioversion at 12 weeks, antiarrhythmic drugs are generally weaned off by the 4 months' mark. We continue to follow all patients after their first 18 months with yearly follow-up.
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Results
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We have performed epicardial HIFU ablation in over 300 patients undergoing concomitant cardiac surgery. Our experience, recently reported in 129 consecutive patients indicated an overall freedom from AF or left atrial tachycardia of 83% at 6 months, 84.5% at 12 months and 86% at 18 months (Table 1). Follow-up was 98% in this series [6]. This patient cohort had rather extensive operative procedures as seen in Table 2
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The detailed early and late morbidity and, mortality observed in this series as well as the efficacy data have been discussed extensively in a previous publication [6].
The use of an off-pump epicardial ablation has allowed us to perform AF ablation in over 90% of patients with AF at the time of their cardiac procedure. The off-pump epicardial approach facilitates the AF ablation in patients with significantly diminished LV function, congestive heart failure and complicated cardiac repairs, patients that frequently appear not to be treated with procedures requiring increased ischemic or cardiopulmonary bypass times. Finally, the performance of epicardial AF ablation has been particularly well suited to patients who do not require left atrial opening, i.e. CABG or aortic valve patients. In this group of patients who require a lesion set more than just pulmonary vein isolation, the ability to ablate these patients while incorporating a mitral isthmus line ablation seems particularly well suited from the epicardium [7].
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Footnotes
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1 Dr. Groh is a consultant to the AF Division of St. Jude Medical. 
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References
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- Gammie JS, Haddad M, Milford-Beland S, Welke KF, Ferguson TB Jr, O'Brien SM, Griffith BP, Peterson ED. Atrial fibrillation correction surgery: lessons from the Society of Thoracic Surgeons National Cardiac Database. Ann Thorac Surg 2008;85:909–915.[Abstract/Free Full Text]
- Ngaage DL, Schaff HV, Mullany CJ, Barnes S, Dearani JA, Daly RC, Orszulak TA, Sundt TM 3rd. Influence of preoperative atrial fibrillation on late results of mitral repair: is concomitant ablation justified? Ann Thorac Surg 2007;84:434–442; discussion 442–443.[Abstract/Free Full Text]
- Ngaage DL, Schaff HV, Barnes SA, Sundt TM 3rd, Mullany CJ, Dearani JA, Daly RC, Orszulak TA. Prognostic implications of preoperative atrial fibrillation in patients undergoing aortic valve replacement: is there an argument for concomitant arrhythmia surgery? Ann Thorac Surg 2006;82:1392–1399.[Abstract/Free Full Text]
- Ngaage DL, Schaff HV, Mullany CJ, Sundt TM 3rd, Dearani JA, Barnes S, Daly RC, Orszulak TA. Does preoperative atrial fibrillation influence early and late outcomes after coronary artery bypass grafting? J Thorac Cardiovasc Surg 2007;133:182–189.[Abstract/Free Full Text]
- Ninet J, Roques X, Seitelberger R, Deville C, Pomar JL, Robin J, Jegaden O, Wellens F, Wolner E, Vedrinne C, Gottardi R, Orrit J, Billes MA, Hoffmann DA, Cox JL, Champsaur GL. Surgical ablation of atrial fibrillation with off-pump, epicardial, high intensity focused ultrasound: results of a multicenter trial. J Thorac Cardiovasc Surg 2005;130:803–809.[Abstract/Free Full Text]
- Groh MA, Binns OA, Burton HG III, Ely SW, Johnson AM. Ultrasonic cardiac ablation for atrial fibrillation during concomitant cardiac surgery: long-term clinical outcomes. Ann Thorac Surg 2007;84:1978–1983.[Abstract/Free Full Text]
- Groh MA, Binns OA, Burton HG 3rd, Champsaur GL, Ely SW, Johnson AM. Epicardial ultrasonic ablation of atrial fibrillation during concomitant cardiac surgery is a valid option in patients with ischemic heart disease. Circulation 2008;118:S78–S82.[Abstract/Free Full Text]
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Summary
Introduction