Симметричная объемредуцирующая пластика увеличенного левого предсердия: 15-летний клинический опыт

Резюме

Атриомегалия как осложнение заболеваний митрального клапана ведет к нарушению пассажа крови по предсердию, фибрилляции предсердий, нарушениям дыхания и сердечной недостаточности.

Цель - провести анализ лечения одномоментной коррекции всех анатомических и функциональных нарушений, сопровождающих митральный порок, с акцентом на коррекцию атриомегалии путем выполнения оригинальной хирургической объемредуцирующей пластики предсердия.

Методы. С декабря 1998 г. по декабрь 2013 г. выполняли объемредуцирующую пластику левого предсердия (ЛП) у 104 пациентов с патологией митрального клапана, используя оригинальную технику операции ("Мерседес-пластика" ЛП): верхний шов выполняли от верхушки ЛП, чуть выше линии уровня верхних легочных вен; правый и левый швы начинали латеральнее устий нижних легочных вен, причем слева в шов уходило все ушко ЛП. Все 3 швы связывали в центре задней стенки ЛП. У большинства пациентов (87 чел.) диагностирована хроническая форма фибрилляции предсердий, по степени тяжести сердечной недостаточности они относились к IV классу по NYHA (средний возраст - 53,4±11 лет). Вся процедура включала пластику ЛП (104 пациента), трикуспидального клапана (47 пациента), хирургию митрального клапана (104 пациента), пластику правого предсердия (29 пациентов), протезирование аортального клапана (20 пациентов), тромбэктомию из ЛП (7 пациентов), аортокоронарное шунтирование (5 пациентов), имплантацию искусственных хорд (5 пациентов).

Результаты. В госпитальном периоде умерли 2 (1,9%) пациента. Размер ЛП после хирургии уменьшился с 8,3±2,1×6,7±1,4 см (от 5 до 14,5 см) до 5,0±1,3×4,7±1,1 см. Кардиоторакальное соотношение уменьшилось с 0,62±0,04 до 0,53±0,02, угол бифуркации трахеи - с 94,3±5,3° до 76,0±6,3°. Мониторинг за 89 пациентами варьировал от 12 мес до 15 лет, при этом у 54 (60,7%) из них наблюдали стойкий синусовый ритм.

Заключение. Клинические, функциональные и анатомические результаты использования оригинальной хирургической техники симметричной пластики увеличенного ЛП позволяют убежденно говорить о необходимости такого комплексного вмешательства в хирургии запущенных митральных пороков. Эти данные подтверждают гипотезу о роли критической массы и размеров ЛП в возникновении фибрилляции предсердий.

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* Доклад представлен на 25-м конгрессе Всемирного кардиоторакального общества (19-22 сентября 2015 г., Эдинбург, Шотландия).

Ключевые слова:митральный порок, кардиомиопатия, пластика левого предсердия, сердечная недостаточность, фибрилляция предсердий

Клин. и эксперимент. хир. Журн. им. акад. Б.В. Петровского. 2016. № 1. С. 20-26.

Atriomegaly, as a complication of mitral valve disease develops in about 20% of patients. Long-term volume and/or pressure overload leads to remodeling of the myocardium and atrial cavities. Anatomic remodeling in cases of valvular cardiopathy is the basis for electrical remodeling which is characterized by an increase in the mass and internal area of the atrium to larger than the critical level, as well as cicatricial and inflammatory formation in some areas. This leads to development of electrical anisotropia with delayed pulse conductivity and of macro-reentrant and multiple micro-reentrant circuits. A modern experimental study showed that reducing the surface area below a critical area prevented the atria from sustaining atrium fibrillation [1]. The compensatory mechanisms of the atria are less than that of the ventricles, which is why the functional disturbances (both mechanical and electrical) develop more often and at an earlier stage than in cases of remodeling of ventricles [2-8].

In cases of left-sided atriomegaly, the compressive effect of the enlarged left atrium (LA) plays a role in the development and progression of cardiac insufficiency. Volume overload and contractility disturbances of the posterior-basal segment of the left ventricle occur. Compression of the left main bronchus upwards and to the left decreases its lumen and widens the tracheal bifurcation angle. This can cause respiratory insufficiency. Such compressive effects of the LA and their negative prognosis for patients with mitral valve disease have led to the development of various techniques of atrial volume- reduction plasty and resection [9-14].

In this article we present our 15-year clinical experience with symmetric plasty of the LA in patients with mitral valve disease (rheumatic heart disease, dysplasia, cardiomyopathy). While doing this Moscow variant of plasty of the left atrium, we place three placating sutures on the posterior wall of the left atrium at an angle of 120 degrees to each other, which turns out to resemble the shape of the well known logo of the German automobile manufacturer, which has led to the nickname for this surgical procedure, “Mersedes-plasty” of the enlarged LA [19].

Material and methods

During the period from December 1998 to December 2013 we performed symmetric volume-reduction Mer- cedes-plasty of the LA in 104 patients. The preoperative demographic data is presented in Table 1. Additionally, 7 patients had thrombus in the left atrium, 3 had infec- tive endocarditis and for 7 patients the present opera- tion was their second heart operation. Most patients (87 cases) had a chronic (permanent) form of atrial fibril- lation of 1 to 17 years duration (range, 5.3±1.2 years). The main goal of this type of volume-reduction is to al- low for left atrium reverse remodeling to occur, with the hope of achieving normal size and form.

Surgical procedure

The first symmetric Mercedes-plasty of the LA was performed in December 1998. We used a typical approach through the interatrial septum using the A. Carpentier technique. If an intraatrial/intraauricular thrombus was present, thromboectomy was performed. Then the mitral valve surgery was performed for all patients, either MV repair or universal chordae preserving prosthetic replacement; then the plasty of the left atrium was performed (Fig. 1).

At present we perform the left atrium plasty in almost all patients in whom anterior-posterior atrium size exceeds 5 cm. If the atrial size is 5-6 cm we also perform para-annular plasty [10]; then the LA appendage is oversewn (this allows us to correct the sagging of the posterior-basal segment of the left atrium). With an atrial size of 6 cm or greater the symmetric atrial-plasty of the posterior wall of the left atrium is also performed. Since 2003 we have performed atrial-plasty in conjunction with the suture isolation of the pulmonary vein ostia in hopes of achieving a higher rate of recovery of sinus rhythm.

The first continuous Prolene-3,0 suture is started at the upper edge of the left atrial appendage (the left one). The appendage orifice is sutured closed and then the suture is extended to the middle of the atrium. In this area we deviate about 10 mm from the mitral valve annulus to avoid injury of the circumflex coronary artery.

The second suture (the upper one) is started at the apex of the left atrium, practically at the upper edge of the atriotomy incision. Then placating all the excess tissue of the posterior wall of the left atrium between the ostia of the right and left veins, we extend the suture line in the direction of the mitral valve where it is tied to the first suture. The tissue width plicated by stitches of this suture line can sometimes exceed 50 mm.

The third suture (the right one) is placed para- annular and with it we plicate all excess tissue along side of the mitral valve fibrotic ring; then it is extended to the bottom angle of the atriotomy incision and in the direction where the left and upper sutures will be tied together.

The left and the right sutures remove the excess tissue in the para-annular basal segment of the left atrium, thus shortening its vertical (superior-inferior) size, while the upper suture plicates the excess tissue of the intervenous segment and shortens the transverse (right to left) size of the left atrium. Then we tighten and tie all the three sutures at the fixation point on the posterior wall of the left atrium, thus automatically and symmetrically reducing the anterior-posterior size of the atrium.

Since November 2003 in the patients with the most severe cases of mitral valve disease, atriomegaly and chronic (continuous) atrial fibrillation, we use a modified technique of atrial-plasty with an additional placating suture placed over the ostia of the left pulmonary veins (see Fig. 1). This suture connects the starting points of the first and second suture of the standard atrial-plasty for complete isolation of the left pulmonary veins, which likely increases the rate of recovery of sinus rhythm.

The surgical procedure of symmetric atrial-plasty of the left atrium makes it possible to practically restore to normal values both the volume and the form of the left atrium, while the ostia of the left and right pulmonary veins are joined together into two collectors just above the mitral valve (or prosthesis) (Fig. 2).

After performing the first several operations of the symmetric atrial-plasty of the left atrium, we thought that detailed preoperative echocardiographic analysis would make it possible to calculate individually for each patient the width of tissue to be placated in each of the three sutures lines. However, this task could not be solved practically, since the form of the enlarged atrium (especially the giant LA) was far from a spherical shape. It has the uneven form of a dumbbell, which was confirmed by the IMR- tomography data.

At present we determine the degree of atrial reduction intraoperatively, and the size of the mitral valve prosthesis (27-33 mm) becomes the determining factor. This technique aims at attaining the size of the left atrium of approximately 4cm, while the circumference size should be around 12 cm (thus achieving a reduced size that we have demonstrated is less likely to result in the development and maintenance of fibrillation).

Statistical analysis

Values are presented as means ±standard error of the mean.

Results

This Moscow variant of the atrial-plasty procedure which we developed was performed in 104 patients with left atriomegaly. Among them, 48 patients had our standard plasty, and 56 had the modified atrial- plasty with suture isolation of the left pulmonary veins.

Mitral valve prosthetic repair or replacement was performed in all 104 patients. Other cardiac pathologies and defects of mitral valve disease were also corrected during the operation (Table 2). There were 2 hospital deaths (1.9%).

The size of the LA before surgery was 8.3±2.1×6.7±1.4 cm (range, 5 to 14.5 cm). After the first 12 months following operation the size of the LA was at average 5.0±1.3×4.7±1.1. The IMR- tomography data demonstrated normalization of the para-annular as well as of the posterior intervenous segment of the LA (Fig.3). The cardiothoracic ratio decreased from 0.62±0.04 to 0.53±0.02.

Fig. 3. Transverse IMR- tomogram of patient Z., 44 years old, with aortic- mitral valve disease and atriomegaly: А - before surgery: the transverse size of the left atrium is 11,2 cm; В - after mitral-aortic valve replacement and atrial-plasty of the left atrium: the transverse size of the left atrium is 5,3 cm

The tracheal bifurcation angle decreased from 94.3±5.3 degrees to 76.0±6.3 degrees (Fig. 4). Sinus rhythm before the surgery was detected in only 13 out of 104 surgical patients (12.5%). After the operation, sinus rhythm was restored in an additional 55 patients out of the 89 who underwent the surgery and had preoperative atrial fibrillation (61.8%). Sinus rhythm was restored in 18 patients after the standard atrial-plasty, and after modified atrial-plasty, sinus rhythm was restored in 37 patients. In total, among patients discharged from our hospital, sinus rhythm was recorded in 68 out of 102 patients (66.7%) in the follow-up of 12 months after the surgery. This index was much higher than preoperative. No patient needed electrical cardioversion; they did not receive any antiarrhythmic therapy. All patients had spontaneous restoration of sinus rhythm during the first 6-12 months after surgery.

Fig. 4. Chest X-Ray of patient G., 49 years old. Diagnosis: mitral stenosis, atriomegaly: A - before surgery: the tracheal bifurcation angle is 82° (shown with dotting lines); B - after surgery: the tracheal bifurcation angle is 65°

The follow-up data (questionnaires and hospital check-up is available for 89 (87.3%) patients within 12 months to 14 years after surgery; 54 (60.7%) patients informed us about sinus rhythm, but this is not established fact; 55 (61.8%) patients were in I- II class NYHA.

Discussion

At present we consider the size of the LA in any plane exceeding 5 cm as an indication for volume- reduction plasty, especially when it is accompanied by atrial fibrillation.

The main problem and the risk associated with the left-sided atriomegaly in patients with valvular cardiopathy and cardiac insufficiency is intraatrial thrombus formation and systemic thromboembolism. When the LA volume is several times larger than the stroke volume of the left ventricle, blood congestion develops in the atrial cavity. Such a pathological condition, which far exceeds the normal atrial reservoir function, likely leads to intraauricular and then intraatrial thrombosis. The likelihood of thrombosis greatly increases in the presence of inflammation of any etiology. That is why, according to international recommendations of cardiology and cardiac surgery societies, anticoagulation therapy with oral anticoagulants should be started if the size of the left atrium is 5 cm or greater, irrespective of the cardiac rhythm [15]. We think that such atrial transport dysfunction that is observed in atriomegaly cases (considerably delays blood passage from the pulmonary veins into the left ventricle) is the most serious argument for performing an operation of geometric and volume remodeling of both atrial cavities, which is why we strive to reduce the size of enlarged left atrium to 4 cm during the operation.

Another important factor which leads to thrombus formation (more often intraauricular) and thromboembolism is the development of atrial fibrillation. Loss of contractile function of the atria, as such, doesn’t neccessarily lead to the development of cardiac insufficiency, since quite often the patient doesn’t even notice the time of onset of fibrillation. However, when rapid irregular pulses are passing through the atrioventricular node with a rapid ventricular response, the duration of such dysfunction becomes very important, since it can intensify the cardiopathy. No matter what the reasons are for the development of atrial fibrillation (isolated/idiopathic fibrillation quite often is caused by other mechanisms associated with the conductivity system and can be of genetic origin), after its onset it can become self-supporting, such as a circulus vitiosus [5, 6, 16]. In patients with valvular cardiopathy the atrial fibrillation can considerably aggravate the situation, since it can result in not only frequent but also irregular ventricular response. Clinically it is expressed in the symptom called “pulse deficit”, when 30-40% of ventricular contractions are not followed by adequate cardiac output.

Atrial fibrillation is present in 30-40% of patients with mitral valve disease and in most of these patients the sinus rhythm is not restored after surgical correction of the mitral valve disease, especially when the fibrillation is of three or more month’s duration. When these cases are accompanied by atriomegaly, the possibility of fibrillation grows and can reach 80%. According to the data from most hospitals that are doing Maze atrial remodeling, the patients with organic valve disease enter a separate group in which the myocardial mass of the atria and their size play an important role in the development of fibrillation. The Cox maze procedure is not effective for patients with large LA and recurrent atrium fibrillation because it does not divide the atrium into enough small sections to prevent sustained atrium fibrillation as the critical mass hypothesis predicts [1, 17]. As a rule such patients have continuous fibrillation. Due to morphological peculiarities of cardiopathy the contractile function of the atria is reduced, and that is why restoration of the sinus rhythm in this group of patients cannot be assumed to result in atrial function restoration [12, 18].

Beside the atrial size and mass that are increased in patients with left-sided atriomegaly, of great importance is the state of the atrial myocardium, since it varies in patients with valvular diseases of various etiologies. Yashima et al. (1997) had shown that in patients with mitral insufficiency of non-rheumatic origin, a direct negative correlation is observed between the size of the left atrium and the contractile function after restoration of the sinus rhythm [18]. At the same time there is no such correlation in patients with rheumatic disease, and this likely suggests the role of inflammatory and fibrotic changes in the atrial wall, regardless of what caused the process of anatomic remodeling.

Thus, in patients with valvular cardiopathy and atrial dilatation, restoration of the sinus rhythm is not always accompanied by an adequate increase of the contractile function. So this enlarged cavity serves as a congestion reservoir and a potential source of intraatrial thrombosis and embolism. These patients, in spite of restoration of the sinus rhythm, will stay on anticoagulation therapy all of their lives, even after valvular plasty. In prosthetic valve replacement patients, anticoagulation therapy with oral anticoagulants is needed and therefore the important question remains as to whether volume and rhythm restoring operations are needed in this category of patients.

Along with the presentation of our first clinical cases of atrial plasty [19] we offer a hypothesis which in our view has no serious contra-arguments:

- In patients with heart valve pathologies, espe- cially with cardiopathy and dilatation of the LA, volume-reduction and restoration of the trans- port function play an important role in the pre- vention of non-prosthetic thromboembolism.

- In this group of patients with Maze-type operations, while planning surgical correction of cardiac rhythm, care should be taken not only of electrical but also of anatomic remodeling.

In a number of publications devoted to isolating surgical techniques used for sinus rhythm restoration, it is mentioned that the size of the LA is an important prognostic factor for the success of surgery and the importance of the atrial volume reduction is stressed [4, 12, 20-23].

At present our concept concerning the restoration and maintenance of the sinus rhythm in patients with myocardial dysfunction, atriomegaly and cardiac insufficiency is as follows:

- In all of these patients without exception, we perform atrial volume-reduction plasty.

- In patients who had their sinus rhythm restored but then return to atrial fibrillation, we do not use either antiarrhythmic therapy or electric cardioversion in the immediate and early postoperative period.

- As to the question of restoration of the sinus rhythm, we reconsider this only 3 months after surgery on the basis of the clinical state and central hemodynamics of the patient.

- Low cardiac output, signs of inflammation, the need for diuretic therapy and/or reluctance of the patient are all indications for the support of normal heart rate without additional efforts for restoration of the sinus rhythm.

This approach (which seems quite conservative from the point of surgical arrhythmology) is based on our assurance that in the early postoperative period (when the postoperative repair processes are not completed, the hemodynamic parameters are unstable, and anticoagulation therapy is required). The risk of thromboembolic complications is higher, when the rhythm is changed or unstable, than it is in the presence of fibrillation with a normal ventricular response.

Conclusion

In summary, we believe that clinical, functional and anatomic results support the use of the symmetric plasty for treatment of enlarged left atrium in patients undergoing mitral valve surgery. The proposed variant of the left atrium size restoration facilitated sinus rhythm recovery. This Moscow variant of the left atrium size restoration facilitated sinus rhythm recovery. We believe that in order to increase the effectiveness of rhythm- restoring Maze-type operations, it is necessary to normalize the size of the left atrium, that is, to reduce its size to 4 cm. In the surgical treatment of giant left atrium combined with mitral valve disease, we recommend correction of other concomitant cardiac pathologies during the same operation for the full recovery of intracardiac hemodynamics. These data support the critical mass hypothesis of atrium fibrillation and may aid in better understanding the mechanism of action of new surgical procedures for patients with atrium rhythm disturbances.



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