Asian Cardiovasc Thorac Ann 2005;13:107-111
© 2005 Asia Publishing EXchange Ltd
Effects of Giant Left Atrium on Thromboembolism after Mitral Valve Replacement
Veysel Kutay, MD,
Kaan Kirali, MD1,
Hasan Ekim, MD,
Cevat Yakut, MD
Cardiovascular Surgery Department, Van Yuksek Ihtisas Hospital, Van, Turkey
1 Kosuyolu Heart and Research Hospital, Istanbul, Turkey
For reprint information contact: Veysel Kutay, MD Tel: 90 432 216 8352 Fax: 90 432 216 8352 Email: vkutay{at}yahoo.com, YYU T
p Fak. Araþtrma Hast. KVC Klinik, 65200 Van, Turkey
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ABSTRACT
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The aim of this study was to evaluate the incidence of thromboembolic events in patients with giant left atrium ( > 6.5 cm) after mitral valve replacement. From January 2000 to September 2002, a total of 126 patients who had undergone mitral valve replacement were divided into two groups according to the presence or absence of giant left atrium. Group A comprised 34 patients with left atrium over 6.5 cm without compression symptoms and Group B comprised 92 patients. The preoperative variables did not distinguish the patients in each group, except for atrial fibrillation; Group A 85.2% and Group B 61.9% ( p < 0.01). After mitral valve replacement, left atrium mean diameter was significantly decreased in Group A from 8.1 ± 1.3 mm to 6.2 ± 1.6 mm ( p < 0.01). There were no significant differences in thrombosis, hemorrhage and thromboembolism rates in both groups. Postoperative clinical and hemodynamic parameters demonstrated a positive clinical response to mitral valve replacement in patients with giant left atrium. During follow-up no direct relationship between thromboembolism and giant left atrium was evident.
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INTRODUCTION
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The presence of giant left atrium (GLA) and atrial fibrillation (AF) in spite of surgical correction of mitral valve disease, causes stagnation of blood in the left atrium (LA) and consequently increases thromboembolic risk.1 When enlargement of the LA (anteroposterior length) is over 6.5 cm on echocardiography, it is defined as giant left atrium.2 GLA may also cause compression of the adjacent organs such as the middle and lower lobes of the right lung, esophagus, trachea, pulmonary veins and left ventricle.3 Several techniques of LA size reduction combined with mitral valve replacement (MVR) have been reported for the elimination of LA compression symptoms and postoperative complications.4–8 In the present report, LA reduction procedures were not applied in patients with LA size over 6.5 cm. The aim of this study was to compare the thromboembolic complication rates at postoperative follow-up in patients with and without GLA who underwent MVR.
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MATERIALS AND METHODS
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PATIENT SELECTION AND STUDY PROTOCOL
Between January 2000 and September 2002, a total of 126 patients undergoing MVR were divided into two groups according to whether GLA accompanied the mitral lesion. Group A comprised patients with GLA (34 patients: 27%) and Group B comprised patients without GLA (92 patients: 73%). Patients with coronary artery disease or severe aortic valve disease combined with mitral lesions were not included in this study. The mean age of the patients in Group A was 42 ± 11.1 years (range 17 to 58 years) and 39 ± 13.8 years in Group B (range 13 to 64 years). In Group A, 22 (64%) of the patients were female whilst there were 51 (55%) females and 41 males in Group B. The etiology of the mitral disorders was mostly rheumatic in both groups, and the main pathology of the mitral lesion was pure stenosis in 72% of patients in Group A. The Group A patients were 64.7% NYHA class III and 17.6% Class IV, while for Group B patients, 68.4% and 14.1%, respectively ( p = NS). Preoperatively, 85.2% of Group A patients and 61.9% of Group B were in atrial fibrillation ( p < 0.05). Three patients (8.8%) in Group A and seven patients (7.6%) in Group B had undergone previous closed mitral valvotomy ( p = NS). On echocardiographic assessment, preoperative anteroposterior left atrial mean diameter was 8.1 ± 1.3 cm (range 6.8 to 12.5 cm) in Group A and 5.4 ± 0.5 cm (range 4.3 to 6.4 cm) in Group B. In addition to the transthoracic or transesophageal echocardiography, cardiac catheterization and coronary angiography were also performed in patients older than 40 years.
SURGICAL METHOD
All patients were operated on electively, and monoleaflet or bileaflet mechanical mitral prostheses were implanted in patients of both groups. Cardiopulmonary bypass was established by ascending aortic arterial and bicaval venous cannulation after induction of general anesthesia. Diastolic arrest and myocardial protection were supplied by antegrade and retrograde hyperkalemic isothermic blood cardioplegia with moderate hypothermia (30
C). The surgical exposure of the LA was achieved by a vertical left atriotomy posterior to the interatrial groove and anterior to the right pulmonary veins. Whenever a tricuspid valve reconstruction was planned, interatrial septum resection was used for LA exposure via the right atrium. Left atrium reduction procedures were not performed in Group A patients except for left atrial appendage (LAA) internal ligation. LAA internal ligation was effected using 3/0 polypropylene sutures when the LA thrombus resection was performed concomitantly with valve replacement. In addition, an attempt was made to preserve the posterior leaflet especially in patients demonstrating a dominance of mitral valve regurgitation.
ANTICOAGULATION
Low molecular weight heparin (Deltaparine sodium, 2 x 5000 IU•day–1, subcutaneously) was commenced in the third hour of the postoperative period for early anticoagulation. Warfarin sodium (5 mg•day–1) and acetylsalicylic acid (150 mg•day–1) were commenced orally on the first postoperative day in all patients. The dosage of warfarin was regulated with the international normalized ratio (INR) maintained between 2.5 and 3.5.
FOLLOW-UP
The thromboembolic and hemorrhagic complications were documented by hospital records and by direct contact with patients or family. Follow-up was 95.2% completed in all 126 patients. Total follow-up was 226.5 patient-years, with a mean of 1.8 ± 0.7 years (range 0.5 to 3.0 years). Patients with no postoperative symptoms were routinely evaluated by echocardiography on avarage every 6 months during the postoperative period.
STATISTICAL METHODS
Parameters evaluated were age, gender, previous valvular surgery, cardiac rhythm, LA size, NYHA functional class, pulmonary artery pressure, grade of mitral disease, presence of left atrial thrombus, cardiopulmonary bypass time, aortic cross-clamp time, prosthesis type and size, low cardiac output syndrome, infection, pulmonary dysfunction, neurologic deficit, prosthetic valve thrombosis, hemorrhage, major and minor thromboembolism, thrombolytic treatment, urgent re-operation and INR level. The overall thromboembolic and hemorrhagic rates encompassed early (< 30 days) and late events (> 30 days). SPSS version 10.0 software (SPSS, Chicago, IL, USA) was used in data analysis, and p < 0.05 was considered statistically significant. Preoperative and postoperative values were analyzed using the two-independent-sample t test and chi-squared test.
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RESULTS
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HOSPITAL MORTALITY
There was 1 hospital mortality (2.9%) in Group A and 5 (5.4%) in Group B ( p = NS). One patient died in the third week postoperatively as a result of multi-organ failure following left hemiplegia. Two patients, who were operated on for calcific mitral stenosis with severe pulmonary hypertension, died due to pulmonary dysfunction and right heart failure. Two female patients with severe cardiac cachexia died as a consequence of low cardiac output (LCO) during the early postoperative period. Intraoperative and early postoperative parameters are shown in Table 1
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EARLY POSTOPERATIVE DETAILS
Pulmonary artery pressure dropped significantly in both groups postoperatively. During the early postoperative period, the persistence of atrial fibrillation in Group A patients was more apparent than in Group B and conversion to sinus rhythm was significant in Group B as seen in Table 1
. There were no significant differences between the two groups with regard to the use of monoleaflet or bileaflet mechanical prostheses. Three patients in Group B were re-operated on to control bleeding in the early postoperative hours, however no early or late cardiac tamponade was evident due to early heparin anticoagulation. Two patients experienced neurologic deficit: one of these died and the other was discharged with left hemiparesis. Five patients required prolonged ventilatory support. Of these, three patients subsequently died due to LCO and multiple organ failure.
LA REDUCTION AND IMPROVEMENT OF FUNCTIONAL CAPACITY
Between 6 and 12 months postoperatively, LA size reduction was prominent in Group A with a decrease from 8.1 ± 1.3 cm to 6.2 ± 1.6 cm ( p < 0.01). The reduction of LA was more significant in patients with preoperative LA dimensions over 8.0 cm ( p < 0.001). The mean NYHA functional class improvement was also significant in patients of both groups at sixth month postoperatively (2.9 ± 0.8 to 1.2 ± 0.5 and 2.7 ± 1.1 to 1.3 ± 0.6 respectively, p < 0.05).
PROSTHETIC VALVE AND ANTICOAGULANT-RELATED LATE COMPLICATIONS
There were 2 (5.9 %) late valve related deaths in Group A during follow-up and 3 (3.3 %) valve related thrombotic and thromboembolic deaths in Group B ( p = NS). Valve related complications (minor and major CVA, hemorrhage, endocarditis, re-operation or thrombolytic treatment for stuck valve) are detailed in Table 2. At the time of diagnosis of valve thrombosis, management of anticoagulant therapy was inadequate in more than half of the patients according to international recommendations. Of the 10 patients diagnosed with prosthetic valve thrombosis, seven of these (2 patients in Group A and 5 patients in Group B, p = NS) had an INR level below 2.0. Gastrointestinal bleeding in two patients and nasal hemorrhage in one patient due to excessive dosage of warfarin were treated with medical therapy requiring brief hospitalization.
URGENT RE-OPERATION FOR PROSTHESES THROMBOSIS
Two patients in Group B died within one hour after admission to the intensive care unit after failing to respond to cardiopulmonary resuscitation. Four patients underwent re-operation and four patients were managed with thrombolytic therapy. Two of the patients who underwent re-operation died postoperatively due to LCO. Two patients with stuck valves underwent valvular replacement with bileaflet mechanical prostheses and were discharged without any complications.
THROMBOLYTIC TREATMENT FOR PROSTHESES THROMBOSIS
One patient did not respond to thrombolytic treatment and died, while hemodynamic improvement was seen in three patients after streptokinase treatment (0.5 million IU/iv bolus, 2.5 million IU/24 h) significantly decreased the mitral valve gradient. In 1 patient left hemiparesis was seen after thrombolytic treatment. In our protocol, the determination of thrombotic valve treatment between re-operation and thrombolytic treatment depended on the patient’s hemodynamic stability and the duration of any symptoms. If the patients symptoms progressively intensified, re-operation was urgently performed.
LATE THROMBOEMBOLISM AND ATRIAL FIBRILLATION
Major thromboembolism without prosthetic valve thrombosis was seen in one patient in Group A and two patients in Group B. The linearized rate for overall thromboembolism including prosthetic valve thrombosis considering major events for Group A was 6.7% per patient-year (4 of 33 patients) and 5.7% per patient-year (9 of 87 patients) for Group B ( p = NS). For the risk factors of late thromboembolic events and mortality, there were no significant differences between males and females. In addition, there was no correlation between size and type of prosthetic valves and late postoperative thromboembolism. An additional risk factor of late prosthetic valve thrombosis was atrial fibrillation and 75% of the patients who had thromboembolic events or prostheses thrombosis were in AF. Although AF was seen more frequently in Group A patients, there was no correlation between GLA and late thromboembolic complications during follow up.
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DISCUSSION
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The major valve related complications of mechanical mitral prostheses are thromboembolism including thrombosis and anticoagulant hemorrhage. Postoperative LA thrombus may develop as early as during the operation. Left atrial thrombus involving the interatrial septum incision site, posterior wall, or the sewing ring was found in 61% of patients who died within 60 days of mitral valve replacement.9 The thrombosis risk is higher in the first 5 postoperative years and once an event has occurred, the risk of subsequent events is increased.10 The diagnostic evaluation of prosthetic valve thrombosis involves complementary approaches. Echocardiography, cinefluoroscopy and the clinical situation of the patient are usually sufficient to assess obstructive thrombosis. The management has changed over time due to better understanding of the pathogenic mechanism of thrombosis, the advent of more accurate diagnostic procedures and the improvement of surgical techniques.
Mechanical prostheses have been used for 40 years as substitutes for diseased native valves. The extent of patient follow-up, the adequacy of anticoagulation management and depth of evaluation are likely contributing factors to the reported series. There are various reports comparing the performance and thromboembolic incidence of bileaflet or monoleaflet mechanical mitral prostheses. The overall thromboembolic rate for mitral replacements ranged from 1.6% per patient-year to 5.5% per patient-year.11–13 Although our thromboembolic rate was higher than others, we did not find any significant differences between monoleaflet and bileaflet prostheses for thrombosis episodes and thromboembolic rates. However, a strong correlation was found between patients socioeconomic status and irregular using of oral anticoagulant therapy. Of the patients who had thrombotic mitral prostheses, 73% were uneducated and had irregular anticoagulation control and infrequent prothrombin time assessments.
The size of LA is another independent predictor of thromboembolism. Miscellaneous surgical techniques such as posterior and para-annular plication, partial resections and triangular atriectomies have been suggested for diminishing the size of LA and preventing stagnation.3–8 Although the majority of these techniques are performed with an acceptably low risk, surgeons must keep in mind the possibility of postoperative bleeding especially in extended resections, pulmonary vein obstruction, circumflex coronary artery injury and prolonged aortic cross-clamp time. In our series, spontaneous LA reduction after MVR during the 6–12 month postoperative term was significant yet conversion to sinus rhythm was not significant/sufficient. Similar results were reported by Tonguc et al5 who failed to find any difference between plicated and non-plicated patients with regard to hemodynamic status and reduction of LA diameter.
The surgical techniques that have been proposed for the restoration of sinus rhythm combined with mitral valve procedures have not been specially designed to diminish LA size.14,15 Isobe and Kawashima demonstrated that LA diameter of more than 8 cm was the most important factor in the reccurence of AF.15 The technique described by Garcia-Villarreal et al in 4 patients demonstrated rapid restoration of sinus rhythm in addition to significant reduction in LA size.6 In many instances, the restoration and maintenance of sinus rhythm is time consuming and quite difficult to achieve especially in patients whose LA diameter is over 8 cm.15,16 An additional issue concerns the relief of compression symptoms of adjacent organs due to GLA. We could not determine the manifest compression of surrounding structures due to LA enlargement. If we had, a partial LA resection technique might have been an appropriate option. We also observed rapid hemodynamic improvement in the early postoperative course in the GLA group as well as in Group B without any respiratory failure during weaning from the ventilatory support.
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CONCLUSION
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Postoperative clinical and hemodynamic parameters showed a positive response to MVR in patients with GLA. A direct correlation between early or late thromboembolism and GLA was not found. Inadequate control of anticoagulation level was a major risk factor for thromboembolism faced during follow-up, especially in patients dwelling in rural areas.
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TOP
ABSTRACT
INTRODUCTION
