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Ann Thorac Surg 2000;70:1080-1082
© 2000 The Society of Thoracic Surgeons

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Supplement: cardiothoracic techniques & technologies

Combined stentless mitral valve implantation and radiofrequency ablation

^a Department of Heart Surgery, University of Leipzig, Leipzig, Germany
^b Department of Cardiology, Heartcenter, University of Leipzig, Leipzig, Germany

Address reprint requests to Dr Walther, Heart Center, University of Leipzig, Russenstrasse 19, 04289 Leipzig, Germany
e-mail: walt{at}medizin.uni-leipzig.de

Presented at the Sixth Annual Cardiothoracic Techniques and Technologies Meeting 2000, Ft Lauderdale, FL, Jan 27–29, 2000.

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. The aim of this study was to evaluate the results of combined stentless mitral valve (SMV) replacement and intraoperative radiofrequency ablation for chronic atrial fibrillation (IRAAF) to restore physiologic hemodynamic function.

Methods. Since July 1998 12 patients (72 ± 4 years, 10 women, mitral stenosis/mitral incompetence 8/4, NYHA 3.3 ± 0.4, CI 1.8 ± 0.5) had SMV implantation and received additional IRAAF by inducing continuous left atrial lesion lines from the MV annulus to all four pulmonary veins and to the atriotomy.

Results. The flexible SMV was implanted at the papillary muscles and at the annulus using a conventional (n = 6) or a minimally invasive approach (n = 6). Sinus rhythm was successfully restored in 10 of 12 patients with 6- and 12-months’ follow-up; 2 required DDD-pacemaker implantation. However, in the early postoperative period several interventions including medical treatment (sotalol or amiodarone) in 9 and electrical cardioversion in 7 patients was required. Two patients required reinterventions: 1 cardioversion and 1 amiodarone medication after 3 and 6 months, respectively. At echocardiography the SMV demonstrated good hemodynamic function and atrial contraction.

Conclusions. Restoration of physiologic cardiac function by SMV implantation and IRAAF is advantageous and no further anticoagulation is required.

	Introduction

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Significant mitral valve (MV) disease is often associated with chronic atrial fibrillation (AF) and left atrial enlargement due to pressure or volume overload. Valve replacement has to be performed whenever MV reconstruction is not feasible, as in some cases with degenerative disease. In these patients valve selection is still controversial as no ideal prosthesis is available. Whereas stented conventional bioprostheses are at a high risk for structural failure, mechanical valves are associated with the need for lifelong anticoagulation, thromboembolic events, and hemorrhages [1].

Recently, a stentless MV (SMV) (Quattro, St. Jude Medical Inc, St. Paul, MN) has been implanted with good early clinical results [2–4]. This pericardial valve is flexible and supported by chordae that are attached to the native papillary muscles. By its design the Quattro valve preserves the annuloventricular continuity. No long-term anticoagulation is required when sinus rhythm (SR) is present in these patients. As soon as long-term durability is proved this valve may be the MV prosthesis of choice.

To restore both physiologic MV function and cardiac rhythm SMV implantation was combined with intraoperative radiofrequency ablation for atrial fibrillation (IRAAF). The aim of this study was to evaluate the perioperative and the early follow-up results of the combined therapy.

	Material and methods

Top Abstract Introduction Material and methods Results Comment References

 
Patients
Since July 1998 12 patients had SMV implantation and received additional IRAAF therapy for concomitant chronic AF persisting for longer than 6 months. This is a subset of the total of 38 patients who received a SMV from August 1997 onwards. Ethical approval was obtained and all patients gave written informed consent. For the 12 patients preoperative demographics are given in Table 1. Preoperative New York Heart Association (NYHA) functional status was 3.3 ± 0.4, ejection fraction 61 ± 13%, body surface area 1.69 ± 0.2 m², and cardiac index 1.8 ± 0.5 L · min^-1 · m^-2. Follow-up was performed after 6 and 12 months and annually thereafter and included physical examination, electrocardiogram, echocardiography, and Holter-electrocardiographic monitoring. No patient was lost to follow-up.

Intraoperative radiofrequency ablation of atrial fibrillation
The relatively new concept of IRAAF has been described by our group [5]. Experimental investigations have proved that it is possible to induce continuous transmural lesion lines without endocardial disruption or perforation [6]. The left atrial approach was used to eliminate macro-reentrant circuits involving isolation of all pulmonary veins and the mitral annulus. Intraoperatively a specifically designed ablation probe with a T-shaped 10-mm tip electrode (Sulzer-Osypka GmbH, Grenzach-Wyhlen, Germany) was used. After opening the left atrium, IRAAF was performed under direct vision. Continuous lesion lines were placed endocardially with temperature-guided radiofrequency energy applications. A schematic drawing of the surgeon’s view is shown in Figure 1. Lesion lines are induced from the posterolateral mitral valve annulus to the left lower pulmonary vein (PV), then from the left lower to the left upper PV, from the left upper to the right upper PV, from the right upper to the right lower PV, and finally from the right lower PV to the atriotomy incision. The whole procedure is performed in a bloodless field.

View larger version (27K): [in this window] [in a new window]   Fig 1. Intraoperative radiofrequency ablation of atrial fibrillation. Surgical view after opening the left atrium, cranial is left. Contiguous left atrial lesion lines are induced from the posterolateral mitral valve annulus to the left lower pulmonary vein (LLPV), to the left upper PV (LUPV), to the right upper PV (RUPV), to the right lower PV (RLPV), and to the atriotomy. (App. = left aftrial appendages; MV = mitral valve).

Implantation of the SMV has been described before [3]. The diseased MV was excised completely and the SMV implanted at the papillary muscles and at the MV annulus thus preserving the annuloventricular continuity. Echocardiography was performed by two experienced examiners using a transthoracic or a transesophageal (TEE) approach at standard views when indicated. Intraoperative TEE was used to guide the sizing procedure while measuring under hemodynamically stable conditions. Cardiac morphology (chamber and wall sizes, wall motion, valve structure), cardiac function (fractional shortening, ejection fraction), and transvalvular hemodynamics (Doppler and color Doppler) were assessed.

Postoperative valve-related morbidity and mortality was evaluated according to standard guidelines [7]. Results are given as mean ± standard deviation. Absolute and relative frequencies were calculated.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
Stentless mitral valve implantation and IRAAF were performed safely in all 12 patients when attempted. The IRAAF therapy required an additional 19 ± 5 min of cross-clamp time. Nevertheless this additional time did not impair the postoperative outcome. Overall perioperative and follow-up results are given in Table 1. Both the sternotomy (n = 6) and minimally invasive right thoracotomy approach (n = 6) provided good access for valve implantation and IRAAF. One of the patients received an additional bypass graft to the left anterior descending coronary artery and 2 had tricuspid valve repair using the de Vega technique.

Preoperative left atrial size had been 66 ± 15 mm (range 49 to 100 mm). In 1 patient with a 100-mm left atrium severe MV stenosis had been present and additional left atrial reduction was performed. All 12 patients were discharged either in SR (n = 10) or after DDD-pacemaker implantation due to III° atrioventricular block (n = 2). However, several interventions had to be performed during the initial in-hospital stay. These included medical therapy using sotalol in 7 and using amiodarone in 2 patients, respectively. Electrical cardioversion had to be performed in 7 of the 10 patients. Thus far follow-up consists of 5 patients at 1 year, 6 patients at 6 months, and 1 patient at 3 months. All were still in SR. Repeat interventions during follow-up were necessary in 2 patients as given in Table 1. Through these repeat interventions stable SR was reestablished in all patients and left atrial contraction was confirmed by TEE. One patient who had received a DDD pacemaker due to a III° atrioventricular block postoperatively had to undergo reoperation after 9 months for paravalvular leak. He received a mechanical valve but subsequently died in the intensive care unit due to sepsis and multiple organ failure.

All other patients were in NYHA functional class I or II postoperatively and were discharged from the hospital in time according to the German standards. Continuous anticoagulation therapy (warfarin) was prescribed only if additional AF was present.

Echocardiography revealed normal MV function postoperatively and at 6- and 12-months’ follow-up in the other 11 patients: Left ventricular ejection fraction increased from 53% ± 12% (postoperatively) to 59% ± 16% (6 months) and 58% ± 11% (12 months). Maximum transmitral bloodflow velocity was 1.6 ± 0.2, 1.65 ± 0.3, and 1.7 ± 0.5 m/s, mean pressure gradient 3.6 ± 1.6, 4.2 ± 1.8, and 4.2 ± 1.7 mm Hg, and MV opening area 2.7 ± 0.3, 2.5 ± 0.4, and 2.7 ± 0.5 cm², respectively. Mild transvalvular reflux was seen in 5, 3, and 1 patients at each follow-up time. Mitral valve orifice area indices were in the normal range as well. Normal hemodynamic function in conjunction with SR after IRAAF therapy contributed to the clinical improvement of the patients.

	Comment

Top Abstract Introduction Material and methods Results Comment References

 
In patients requiring MV replacement complete restoration of hemodynamic function can be expected only for a prosthesis that has all of the features of the native MV is easy to implant, and durable [3]. Most importantly the valve should be flexible and the annulo-ventricular continuity should be preserved [8]. The SMV (Quattro) meets most of these criteria [2–4]. However, only short-term follow-up is available at the moment.

Outcome after MV operation is influenced not only by the type of valve that is implanted but also by persisting chronic AF. These patients have a reduced quality of life due to impaired hemodynamic function, need for long-term systemic anticoagulation therapy, and the increased risk of thrombembolic events. To restore both close to physiologic MV function and SR the combined approach was chosen. The postoperative and early follow-up results of the combined approach is promising. None of the patients required long-term systemic anticoagulation therapy and all were in SR. Nevertheless intermittent interventions have been frequent, mostly caused by the onset of atypical atrial flutter following IRAAF therapy. This finding has been described in another series as well [5]. With adequate medication and in some patients additional electrical cardioversion SR can be reestablished yielding a favorable outcome for the patients. To perform IRAAF therapy an additional cross-clamp time of about 20 minutes is required. With liberal delivery of cardioplegia to protect the heart we did not observe any negative impact for prolonged cross-clamp times.

A clinically relevant hemodynamic benefit of a functional left atrium with active left ventricular filling remains to be proved by larger clinical series in the future. The IRAAF technique itself can be performed relatively easily using a conventional or a minimally invasive approach. With a minimally invasive approach the combination of direct and videoscopic vision allow a better view of the valve and the left atrium than a conventional sternotomy. Thus, IRAAF can be performed precisely through a limited right minithoracotomy. A well-visualized lesion line has to be induced with a stable preselected probe tip temperature. Based on catheter stability the probe was initially withdrawn after 20 to 30 seconds [5]. Meanwhile to achieve an even better success rate the duration for each step was extended to about 40 seconds. Both applications were safe and effective. No thromboembolic events were encountered during follow-up so that the current protocol of no systemic anticoagulation therapy can be pursued in these patients.

In summary the combined approach of SMV implantation and IRAAF to restore both physiologic MV function and cardiac rhythm is a safe and effective therapy. Nevertheless longer follow-up is required.

	References

Top Abstract Introduction Material and methods Results Comment References

 

1. Edmunds L.H., Jr Thrombotic and bleeding complications of prosthetic heart valves. Ann Thorac Surg 1987;44:430-445.[Abstract]
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3. Walther T., Walther C., Falk V., et al. Early clinical results after stentless mitral valve implantation and comparison to conventional valve repair or replacement. Circulation 1999;100(Suppl II):II78-II83.
4. Walther T., Walther C., Falk V., et al. Quadrileaflet stentless mitral valve replacement. Thorac Cardiovasc Surg 1999;47:357-360.[Medline]
5. Kottkamp H., Hindricks G., Hammel D., et al. Intraoperative radiotherapy ablation of chronic atrial fibrillation. J Cardiovasc Electrophysiol 1999;10:772-780.[Medline]
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7. Edmunds L.H., Jr, Clark R.E., Cohn L.H., Grunkemeier G.L., Miller C., Weisel R.D. Guidelines for reporting morbidity and mortality after cardiac valvular operations. Ann Thorac Surg 1996;62:932-935.[Abstract/Free Full Text]
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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Thomas Walther Volkmar Falk Anno Diegeler Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Walther, T. Articles by Mohr, F. W. Search for Related Content PubMed PubMed Citation Articles by Walther, T. Articles by Mohr, F. W.