Surgical treatment of mitral stenosis, complicated by massive thrombosis of the left atrium

Реферат Мета. Проаналізувати особливості хірургічного лікування мітрального стенозу, ускладненого масивним тромбозом лівого передсердя. Матеріали і методи. Аналізовану групу склали 344 пацієнти, прооперовані в Інституті. Масивним тромбоз лівого передсердя вважали, коли тромботичні маси займали не менше третини його об’єму, не рахуючи вушка. Результати. Госпітальна летальність після заміни мітрального клапана становила 4,2% та прямо залежала від ступеня тромбозу лівого передсердя (р < 0,05). Після відкритої мітральної комісуротомії госпітальної летальності не спостерігали, що свідчить про доцільність видалення тромботичної матриці. Висновки. Під час операції з приводу масивного тромбозу лівого передсердя важливо повністю видалити материнську основу тромботичної вистілки та ліквідувати вушко лівого передсердя, що суттєво знижує ризик летальності та тромбоемболічних ускладнень на госпітальному етапі. Комп’ютерна томографія голови та органів черевної порожнини перед операцією є обов’язковою умовою для виключения непомітної тромбоемболії. Ключові слова: масивний тромбоз лівого передсердя; протезування мітрального клапана; відкрита мітральна комісуротомія; штучний кровообіг. Abstract Objective. To analyze the peculiarities of surgical treatment of a mitral stenosis, complicated by massive thrombosis of left atrium. Маterials and methods. The group analyzed, operated in the Institute, consisted of 344 patients. Thrombosis of left atrium was considered a massive, when thrombotic masses have occupied no less than one third of its volume, not mentioning an auricle of atrium. Results. Hospital lethality after change of a mitral valve have constituted 4.2% and directly depended on from a degree of the left atrium thrombosis (р < 0.05). After open mitral comissurotomy hospital lethality was not observed, witnessing the expediency of the thrombosis matrix extraction. Conclusion. During the operation for a massive thrombosis of left atrium it is important to remove a maternal base of thrombotic bed and to eliminate the left atrium auricle, what lowers essentially the risk for lethality and thromboembolic complications on a hospital stage. Doing preoperative computed tomography of head and abdominal organs constitutes obligatory condition for exclusion of a hidden thromboembolism occurrence. Кeywords: massive thrombosis of the left atrium; prosthesis of mitral valve; open mitral comissuroyomy; artificial blood circulation.


Introduction
Left atrium massive thrombosis is one of the complicated mitral valve acquired diseases surgery sections [1,2,4]. It makes 5% in the structure of 4 degree mitral stenosis [6 -10]. Despite existing experience, hospital mortality with the presence of left atrium massive thrombosis still exceeds the limit at mitral stenosis uncomplicated correction [3 -5]. Mitral disease surgical treatment combined with left atrium massive thrombosis is a surgery of elevated risk and is followed by increased hospital mortality due to increased danger of thromboembolic complications during hospital period [4 -8].

Materials and methods
Analyzed group consisted of 344 patients with mitral stenosis, complicated by left atrium massive thrombosis that were on hospital treatment in National M. M. Amosov Institute of Cardiovascular Surgery of National Academy of Medical Sciences of Ukraine within the period from January 01, 1984 till January 01, 2015. Left atrium massive thrombosis was diagnosed when thrombotic masses occupied not less than one third of atrium volume, excluding its appendage. Pure or prevailing mitral stenosis was observed in all cases. 95 (27.6%) patients were in class III of New York Heart Association Functional Classification (NYHA) and 249 (72.4%) patients -in class IV. Patients with assident aortic valve correction were excluded from the study.

Klinichna khirurhiia
Left atrium mitral thrombosis spread level was not even, staring from 33% of left atrium volume up to subtotal, what in turn defined the unevenness of clinical course. This made it necessary to classify the patients in 3 degrees of left atrium mitral thrombosis, depending on correlation of thrombotic masses and left atrium size. I degree included 33 (9.6%) patients with thrombotic masses volume of 33% of atrium volume, II degree -102 (29.7%) patients with thrombotic mass volume within 34 -50% from left atrium volume and III degree -209 (60.8%) patients with thrombotic mass volume from 51% and upwards from left atrium volume.
The distinctive feature of left atrium mitral thrombosis is a dense adherence between thrombotic tissue base ("matrix") and left atrium endocardium, apart from thrombotic mass volume deposition. It concerns first of all II and III degrees of left atrium mitral thrombosis, where thrombotic mass had dense adherence with left atrium wall (matrix base), including the area of left atrium appendage. In 3 cases of I degree of left atrium mitral thrombosis (33 cases total), left atrium appendage area was not included in thrombosis formation (0.6% in all left atrium mitral thrombosis cases) and in 4 cases (0.8% from all left atrium mitral thrombosis cases) there was a thrombotic tissue in this group.
Offered classification allows severity evaluation of surgery patients, determination of surgery volume and postoperative period forecast. Classification of a number of clinical parameters depending on left atrium mitral thrombosis degree is shown in Table 1.
According to the data from Table 1, the values of I degree of left atrium mitral thrombosis patients were significantly different from other patients' values with II and III degree of left atrium mitral thrombosis (р < 0.05). It fully corresponded to the pathology anatomic substrate. In fact, the values in patients with III degree of left atrium mitral thrombosis were clinically the most severe, showing extreme risk of surgery due to long presence of rheumatic disease and atrium fibrillation.
Thromboembolia of systemic blood circulation vessels was observed in 79 patients' past medical history (22.9%), 15 from them (4.4%) had it multiple times. It was a pathognomonic criterion for this patients' category (every fifth). Permanent atrium fibrillation with average duration of (3.5 ± 0.5) years and rheumatic disease with average duration of (21.1 ± 4.5) years were observed in all patients. Thromboembolic complications were observed during (2.1 ± 0.3) years before surgery. It is also important to mention, that in 13 (3.8%) cases such complications were not noticed by the patients and were discovered only during autopsy (post-stroke cysts of brain, kidneys and spleen). This happened during left atrium mitral thrombosis formation, when small thrombus seeding took place unnoticed by the patients and without clinical expression. In any case, preoperative thromboembolic complications (obvious and hidden) influenced patients' clinical course. For this reason, it is always necessary to perform complete body CT-scan in all patients with left atrium mitral thrombosis before surgery.
In the majority of preoperative thromboembolic complication cases thromboembolia in brain vessels dominated in 71 patients (89.8% of patients with thromboembolia), including 3 patients with retina vessel thromboembolia. 19 (28.4% from all patients with thromboembolia in brain vessels) patients among them had residual effects of cerebral circulation disorders in the form of hemiparesis at the moment of admission to the hospital.
Preoperational thromboembolic complications were observed in I degree of left atrium mitral thrombosis in 18.2% (n = 6/33), in II degree in 21.6% (n = 22/102) and in III degree in 24.4% (n = 51/209) (p < 0.05). Thus, a direct proportion between thromboembolic complications prior to surgery and intensity of left atrium mitral thrombosis was observed.
All patients had high tendency to thrombogenesis and apart from atrium fibrillation it was also determined by such blood values as: hemoglobin (159.1 ± 14.5) g/l, hematocrit 0.46 ± 0.02 and thrombocytes 280.5± 14.5.
Within the last 30 years, surgery methods have been noticeably changed. For this reason, the description of the last decade developments are mentioned. The surgeries were carried out in artificial blood circulation conditions, moderate hypothermia (27 -32 C) with cold crystalloid cardioplegia (mostly Custodiol). Aorta compression time was 93.2 ± 18.2 min. and artificial blood circulation time was 133.2 ± 21.5 min.
Mitral valve replacement was made in the majority of cases -301 (87.5%) due to its noticeable deformation (calcinosis and rough fibrosis). Valve reconstruction (open mitral commissurotomy) was performed only in 43 (12.5%) cases.
In case of mitral valve moderate fibrosis and single small calcium inclusions, there was a reconstruction performed in a form of open mitral commissurotomy in 43 (12.5%) patients, in 4 (9.3%) of them it was followed by Reed commissurotomy.
Optimally, when massive thrombosis of left atrium is present, thrombotic mass was eliminated together with its matrix base (1 -9). This procedure has a principal meaning, because the remaining rough surface on left atrium wall leads to thrombotic mass deposit relapse on it in early and longterm postoperative period, which in turn leads to thromboembolic complications.
During each surgery the endeavors were made to remove all thrombotic mass as well as the thrombus base, which usually was a well formed connective tissue with dense adherence to atrium wall. Base was removed together with subiculum, and the remaining surface looked a little bit uneven and rough. Fibrin strands were left, which had to be additionally removed by a swab. The area between atrium wall and thrombus was made wider step by step, reaching to other pulmonary vein entrances and mitral valve fibrotic ring. As a rule, calcification of thrombus inner layers (7 cases) was not an obstacle for thrombus mobilization. There were significant difficulties, however, during thrombus detachment from calcinated atrium wall.
Removal of thrombotic mass together with matrix base is considered a radical method, while removal of throm-botic mass only and keeping of matrix base is considered a partial method. Radical method was used in 138 (45.8% -n = 138/301) patients and partial one -in 163 (54.2% -n = 163/301) during mitral valve replacement. Radical method was used in 23 (53.5% -n= 23/43) patients and partial onein 20 (46.5% -n = 20/43) patients during open mitral commissurotomy. Left atrium chamber was washed with 0.5 liter of normal saline after all thrombotic mass removal, covering left atrioventricular opening with gauze wipe. After that, left atrium thorough visual inspection was carried out. Same inspection and also of left ventricular chamber was made after mitral valve leaflet division or excision.
Radical methods division of left atrium mitral thrombosis (matrix base) removal according to left atrium mitral thrombosis degree is shown in Table 2.
According to Table 2, the possibility of thrombotic mass radical removal proportionally decreases at thrombotic mass deposit increase.
There is a danger of left atrium wall bursting during thrombotic mass radical removal, which was observed in 7 (2.0% -n = 7/344) patients. All bursting events were observed in patients with III degree of left atrium mitral thrombosis 3.3% (n = 7/209). None of the cases resulted in cause of death. Mitral valve replacement was done in 6 cases and open mitral commissurotomy in 1 case. Autopericardiac patch was used in burst area in 3 cases. Usual suture was performed in 4 other cases.
Left atrium appendage manipulations are the second important element of thromboembolic complication cause removal and thromboembolic threats in general. The reason is that appendage ligation (inside suture or outside tie) is an obligatory component of left atrium mitral thrombosis surgical treatment in patients with left atrium mitral thrombosis and predisposition to thrombus formation as the most important pathology element (1,5,8,9). Appendage was ligated in 161 (46.8%) patients. Appendage internal suture was performed in 107 (66.5% -in ligated appendages) patients, outside tie -in 44 (33.5%). Left atrium appendage was ligated after previous mitral valve surgery, which was closed mitral commissurotomy, in 104 patients. Thus, left atrium appendage was ligated in 256 (74.4%) patients.
Variant division of base removal and left atrium appendage ligation according to left atrium mitral thrombosis degree is shown in Table 3.
According to Table 3, radical correction variant 1 was used by I degree of left atrium mitral thrombosis in 78.8% cases, II degree -in 48.0% cases and by III degree -in 33.4% cases (р < 0.05). This proves inverse relevance between the possibility decrease of thrombotic mass radical removal and left atrium thrombotic mass deposit degree. The same trend was observed in all other 3 variants.
Variant division of thromboembolic complication preventive measures (base removal / left atrium appendage