MMCTS
(August 27, 2009). doi:10.1510/mmcts.2008.003301
Copyright © 2009 European Association for Cardio-thoracic Surgery
Procedure
Incisional left atrial isolation for ablation of atrial fibrillation in mitral valve surgery
Angelo Graffignaa,*,
Stefano Branzolia,
Stefano Sinellia and
Mario Viganob
a Cardiac Surgery Unit, Ospedale S.Chiara, Trento, Italy
b Centro Cardiochirurgico ‘Charles Dubost’, University of Pavia, Italy
* Corresponding author: Tel.: +39-461-903 346; fax: +39-461-903 345. angelo.graffigna{at}apss.tn.it
 |
Summary
|
|---|
The renewed interest in surgical techniques for atrial fibrillation (AF) limited to the left atrium has risen the importance of the original technique of left atrial isolation by means of surgical incision. Transmurality of lesions and cost containment are strong elements to be appreciated in this technique.
Key Words: Atrial fibrillation • Mitral valve disease • Surgical ablation
|
Introduction
|
|---|
Left atrial isolation was first described by Williams for diverse supraventricular arrhythmias [1], and is one of the earliest surgical techniques described for ablation of atrial fibrillation (AF) [2] in patients undergoing mitral valve surgery. The rationale of the procedure is to create anatomical blocks to inter-atrial conduction so that AF/flutter is entrapped within the isolated left atrium.
|
Surgical technique
|
|---|
The original technique of left atrial isolation was essentially based on a standard left paraseptal atriotomy that was extended anteriorly to the left atrial appendage (LAA) and posteriorly towards the posterior commissure. Cryoablations were applied to interrupt conduction along the mitral valve annulus at both ends (Schematic 1).
View larger version (60K):
[in this window]
[in a new window]
|
Schematic 1 Vertical trans-septal atriotomy.
Incision is conducted from the right atrial appendage towards the right superior pulmonary vein. From here, an incision is conducted to the fossa ovalis (dotted line).
|
|
As our current approach to the mitral valve is based on a bi-atrial trans-septal approach according to Dubost, a modification of the technique was deemed necessary due to myocardial protection technique.
Cardiopulmonary bypass
Extracorporeal circulation is performed with selective caval venous cannulation. Intermittent cold cardioplegia is administered at the aortic root and sequential doses delivered retrogradely by means of direct coronary sinus cannulation.
Sequence of steps
In order to coordinate the mitral valve and the incisional surgical times, it may be advisable to follow this sequence:
- Trans-septal atriotomy. A transverse right atriotomy is performed heading towards the right superior pulmonary vein (RSPV); atrial septum is incised from this point down to the fossa ovalis (Schematics 1 and 2; Video 1).
- Cryoablation between the mitral valve annulus and the LAA is performed before a prosthesis or a plasty ring is seated. A re-usable cryoprobe with a 1.5-cm tip (FrigitronicsTM) is applied at –60 °C for 120 s (Videos 2, and 3). During cryoablation, sutures may be placed on the other segments of the annulus.
- Mitral valve excision or intra-annular repair. Prosthetic or ring sutures are positioned on the frozen segments once these are completely defrosted.
- Inferior line incision:
- From the RSPV, an incision is performed towards the mitral valve annulus, passing close to the right inferior pulmonary vein (PV), and ending at a variable distance from the mitral valve annulus, according to the anatomical position of the coronary sinus (Video 4).
- The remaining isthmus is cryoablated from the endocardial side. An additional application must be performed on the epicardial surface of the coronary sinus, as inter-atrial conduction might take place from muscular fibers coursing along its dorsal surface (Video 5).
- Positioning of the mitral valve prosthesis or ring (Video 6).
- Reconstruction of the inferior incision with standard 5/0 prolene suture (Video 7).
- Superior line incision
- From the RSPV, an incision performed on the roof of the left atrium, boarding the left superior PV and ending into the superior part of the LAA (Video 8).
- LAA is closed by means of running sutures with standard 5/0 prolene. With the same suture, the superior line is reconstructed (Video 9).
- Suture of the atrial septum incision (Video 10).
- Suture of the right atrial incision (Video 11).
- Check of left atrial isolation and inter-nodal conduction (Video 12).
View larger version (54K):
[in this window]
[in a new window]
|
Schematic 2 Left atrial isolation.
Inferior incision is conducted from the right superior pulmonary vein, towards the inferior pulmonary vein, and towards the postero-medial commissure, leaving an isthmus that is cryoablated (red dot).
Superior incision is conducted from the right superior pulmonary vein, to the left superior pulmonary vein, and into the superior aspect of the left atrial appendage. Cryoablation (red dot) is applied between the mitral valve annulus and left atrial appendage.
|
|
Click on image to view video |
Video 1 Transeptal incision. Ordinary approach to mitral valve is the vertical transeptal atriotomy.
|
|
Click on image to view video |
Video 2 Superior cryoablation. A 2-cm probe is applied for 120' at –60 °C on the isthmus between left atrial appendage and mitral valve annulus.
|
|
Click on image to view video |
Video 3 Superior cryo defrost. After 120', saline is poured onto the probe to facilitate defrost.
|
|
Click on image to view video |
Video 4 Inferior line incision. Probably the most tricky point of the procedure. Care must be taken in order to avoid severing the coronary sinus. Although exceptional, if this happens, repair may be performed by means of subsequent suture of the line.
|
|
Click on image to view video |
Video 5 Inferior cryoablation. Cryoablation is applied onto the isthmus left between the ending of the previous incision and the mitral valve annulus. In order to be complete, cryoablation of the dorsal aspect of the coronary sinus is deemed mandatory.
|
|
Click on image to view video |
Video 6 Ring positioning. Positioning of a mitral valve ring (or prosthesis, if a replacement is being performed) takes place at this point.
|
|
Click on image to view video |
Video 7 Suture of inferior line. With 5/0 prolene, the inferior line incision is reconstructed. This is the point that can be accessed with great difficulty in case of bleeding.
|
|
Click on image to view video |
Video 8 Superior line incision. The incision can be performed from inside the left atrium or, in case of poor viewing, from the transverse sinus, between the superior vena cava and the aortic root.
|
|
Click on image to view video |
Video 9 Suture of LAA and superior line. With a single suture, the left atrial appendage is closed and the superior line reconstructed. Access to this suture can be obtained from the transverse sinus, between the superior vena cava and the aortic root.
|
|
Click on image to view video |
Video 10 Suture of atrial septum.
|
|
Click on image to view video |
Video 11 Suture of right atrium.
|
|
Click on image to view video |
Video 12 Check of isolation and conduction. A pair of epicardial electrodes are positioned on the isolated area (best onto the right superior pulmonary vein) in order to detect complete isolation by means of pacing. This can be performed also on postoperative days.
|
|
|
Results
|
|---|
From November 1989 to July 1994 at the Cardiac Surgery Unit of Pavia, the procedure has been applied to ablation of chronic AF in 205 patients undergoing mitral valve surgery [3], with a hospital mortality of 3%. Patients were routinarily treated with amiodarone. After a mean follow-up period of 14 months, sinus rhythm recovery and maintenance was more frequent in patients without tricuspid valve involvement (71% vs. 62%). Pacemaker implant was necessary in 1% of patients. Among patients who were in sinus rhythm, the mean A-V conduction was 210 ms.
By means of epicardial wires positioned on the right and left (isolated) atria, recording and pacing of both atria was possible: the isolated left atrium went on fibrillating in 123 cases (60%), showed an intrinsic rhythmic activity in 40 cases (19.5%) and no detectable electrical activity in 34 (16.5%).
Hemodynamic evaluation of left atrial isolation showed that recovery of right atrial function achieved ‘per se’ a hemodynamic gain. Cardiac output was measured:
- under high rate right atrial pacing (200 bpm), thus, vanishing right atrial function and mimicking AF
- under right atrial pacing at a rate comparable with the escaping rate of above (right atrial sinus rhythm)
- under right and left atrial pacing (when possible: bi-atrial sinus rhythm).
The cardiac index increased from an average of 2.25±0.55 l/min/m2 under AF to an average of 2.54±0.58 l/min/m2 under right atrial sinus rhythm (P<0.00018), with a mean percentage increase of 13.58±5.5%. A further, but not significant, increase (P=0.108) was detected under bi-atrial sinus rhythm (2.70±0.92).
From March 2006, the technique has been re-applied at the Cardiac Surgery Unit of Trento on nine patients, seven of which are currently in sinus rhythm (77%) with no necessity of pacemaker implant.
|
Technical considerations
|
|---|
Transmurality
Reliance on incisional isolation of atrial areas provides warranty of transmurality. Leaks in the isolation can be found at the sites of application of cryoablation if this is not properly performed. This may happen if:
- large isthmi are spared from incision and are not extensively cryoablated;
- cryoablation is not applied on the dorsal aspect of the coronary sinus.
The combination of cryoablation is mandatory, in order to complete the electrical isolation along the valvular annulus.
Safety
Direct inspection prevents damage to the vessels coursing along the atrioventricular groove. Coronary sinus may course at a distance from the A-V groove, and can be inadvertently cut open if the inferior line is made coursing too rightwards.
Cryoablation ‘per se’ does not provide any impairment to the integrity of the arteries of the AV junction or to the strength of the mitral valve annulus itself, as taught by the dated experience of surgery of Wolff-Parkinson-White syndrome [4]; we did not observe an increased incidence of prosthetic leaks or perioperative ischemic episodes.
Long-term results showed that sinus rhythm could be restored in 77% of the patients with long-lasting AF, and can practically always be maintained in the long-term (78%).
Efficacy
In the historical experience, a 71% success rate was achieved in selected patients without right atrial enlargement or pulmonary hypertension. The success rate is essentially comparable to that obtained with disposable energy-delivering probes.
Materials
The procedure involves the adoption of re-usable cryoprobes and common surgical instrumentary.
|
Limitations of the procedure
|
|---|
Right atrial enlargement
In patients with long-lasting mitral valve disease, with pulmonary hypertension and tricuspid valve incompetence, sinus rhythm is less likely to be recovered due to the presence of an enlarged right atrium. This limitation is shared with all the techniques addressing the left atrium alone.
Amount of the isolated left atrial surface
When compared with techniques that selectively isolate the right and left PV [5, 6], the extension of the isolated surface is somewhat greater, considering that the area in between the right and left PVs and that between the inferior PVs and the mitral valve annulus are left free to fibrillate or stay still (Schematic 3). This aspect has been allegedly correlated with a greater risk of thromboembolism, although it is questionable that, with an anticoagulant therapy in presence of a mechanical prosthesis or with an antiplatelet therapy in presence of a prosthetic ring, a flat fibrillating 10–20 cm2 area can effectively harbor mural thrombosis.
View larger version (22K):
[in this window]
[in a new window]
|
Schematic 3 Extent of the isolated surface of the left atrium. A) Left atrial isolation; B) Maze procedure; C) bilateral pulmonary veins isolation.
|
|
Beating heart
This technique intrinsically cannot be performed without opening the left atrium, thus preventing its use on a beating-heart basis.
|
Comment
|
|---|
Incisional left atrial isolation is a pristine and archetypal technique for ablation of AF in patients undergoing mitral valve surgery [2].
The technique can be ranked among the AF procedures that limitedly address the left atrium, a category that encompasses the vast majority of techniques currently in use.
The technique affords electrical isolation of an area delimited by the PVs, the LAA and the posterior aspect of the mitral valve annulus.
Incisional left atrial isolation shows the same efficacy rate as other widespread, energy-delivering techniques. Interestingly, the failure rate with incisional left atrial isolation may suggest that postoperatively recurrence of AF could be ascribed to other factors than lack of transmurality, possibly indicating the limitation of the achievable results after AF procedures that address the left atrium alone.
At the time of description, left atrial isolation has been criticized by supporters of the bi-atrial ‘Maze procedure’ for addressing the left atrium alone, but this objection is presently inapplicable, or has to be shared with the vast majority of alternative techniques that are currently in use.
Hemodynamic advantage of recovering right atrial pacing and booster function is demonstrated and can amount to +13% in comparison with AF.
The electrical isolation is achieved by an incisional technique and re-usable material (cryoprobe), thus differentiating from the majority of the present procedures, that are based on disposable, energy-delivering probes.
Although costs should not be put on the foreground in health care, it has to be considered that reduction of running costs is a virtuous and inevitable aspect of current practice.
We personally believe that left atrial isolation provides appreciable results in terms of the recovery of sinus rhythm, affords a sensible increase in cardiac performance, carries a low risk of pacemaker implant and is a simple and fast procedure that can be performed in selected patients with left atrial enlargement.
|
References
|
|---|
- Williams JM, Ungerleider RM, Lofland GK, Cox JL. Left atrial isolation: new technique for the treatment of supraventricular arrhythmias. J Thorac Cardiovasc Surg 1980;80:373–380.[Abstract]
- Graffigna A, Pagani F, Minzioni G, Salerno J, Vigano M. Left atrial isolation associated with mitral valve operations. Ann Thorac Surg 1992;54:1093–1098.[Abstract]
- Vigano M, Graffigna A, Ressia L, Minzioni G, Pagani F, Aiello M, Gazzoli F. Surgery for atrial fibrillation. Eur J Cardiothorac Surg 1996;10:490–497.[Abstract]
- Graffigna A, Pagani F, Vigano M. Surgical treatment of Wolff–Parkinson–White syndrome: epicardial approach without the use of cardiopulmonary bypass. J Card Surg 1993;8:108–116.[Medline]
- Benussi S, Pappone C, Nascimbene S, Oreto G, Caldarola A, Stefano PL, Casati V, Alfieri O. A simple way to treat chronic atrial fibrillation during mitral valve surgery: the epicardial radiofrequency approach. Eur J Cardiothorac Surg 2000;17:524–529.[Abstract/Free Full Text]
- Sueda T, Nagata H, Shikata H, Orihashi K, Morita S, Sueshiro M, Okada K, Matsuura Y. Simple left atrial procedure for chronic atrial fibrillation associated with mitral valve disease. Ann Thorac Surg 1996;62:1796–1800.[Abstract/Free Full Text]
|
|
Top
Summary
Introduction