| BackgroundAtrial fibrillation(AF)is a common arrhythmia in clinic.The occurrence of atrial fibrillation is closely related to the electrical activity,mechanical activity and structuraldisorder of the atrium.Assessment of left atrial anatomy and function is important for clinical risk stratification of cardiovascular disease.Left atrial enlargement indicates an increase in left atrial wall tension,which in turn leads to an increase in left atrial pressure and an increase in capacity load,as well as an impact on left atrial function.Atrial fibrillation is an independent risk factor for stroke.It is important to accurately evaluate and predict the complications of atrial fibrillation,such as thromboembolic events.Left atrial appendage(LAA)is the main site of thrombus formation in patients with atrial fibrillation.It has been proved that LAA occlusion can effectively prevent atrial fibrillation related stroke.Currently,there are various methods for LAA occlusion,including LAA occlusion,LAA suture and LAA resection.Thoracoscopic LAA resection has been proved to be an effective method .Compared with other LAA occlusion,LAA resection is a safe procedure without recanalization of the LAA.It has been reported that the LAA is an anatomic structure of the left atrium,which plays an important role in the storage function of the left atrium .And the reservoir function of the left atrium is inseparable for the occurrence of atrial fibrillation .Meanwhile,the reservoir function of the left atrium is also closely related to atrial fibrillation and stroke.It has been found in literature that the occurrence of unexplained stroke in patients with paroxysmal atrial fibrillation is closely related to the decline of left atrium reservoir strain.For patients with paroxysmal atrial fibrillation or non-paroxysmal atrial fibrillation,the decrease of left atrial reservoir strain is closely related to acute embolism.And the left atrial reservoir function can supplement the CHA2DS2-VASc risk stratification commonly used clinically.MethodsA total of sixty-nine patients with paroxysmal or non-paroxysmal atrial fibrillation were enrolled,including 37 patients with non-paroxysmal atrial fibrillation and 32 patients with paroxysmal atrial fibrillation.All patients in our study had previous history of thromboembolism or stroke.in the enrolled patients,preoperative electrocardiogram,24-hour Holter and transthoracic echocardiography were performed to assess the structure and function of the heart.Organic heart disease,primary pulmonary hypertension,uncontrolled hyperthyroidism,poorly controlled hypertension and patients with poor acoustic windows were excluded.Before the surgery,transesophageal echocardiography or cardiac CT examination was required to exclude left atrial thrombosis.If a blood clot was found before surgery,the operation may be delay or cancelled.After preoperative preparation,all patients were undergone stand-alone minimally invasive radiofrequency ablation plus LAA resecction.No complications occurred during the operation.All patients stopped taking anticoagulant drugs after LAA resection and went to the outpatient department for regular check-up.24-hour Holter and transthoracic echocardiography were performed to evaluate the recovery of atrial fibrillation and cardiac function on one week and three months after the operation.Cardiac CT and craniocerebral MR were performed one year after the operation to assess thromboembolic events.The main parameters evaluated in this study include: left atrial volume(LAV)and left atrial volume index(LAVI).The maximum of left atrial volume(LAVmax)is measured before mitral valve opening and the minimum of left atrial volume(LAVmin)is measure at mitral valve closure.The left atrial volume before atrial systole is measure at the P-wave origin of ECG.The above volumetric measurements were standardized by body surface area.left atrial ejection fraction(LAEF)=(LAVmax-LAVmin)/LAVmaxleft atrial extension index(LAEI)=(LAVmax-LAVmin)/LAVminleft atrial active ejection fraction(AAEF)=LAV-p-LAVmin)/LAV-pconduit volume of left atrium =[LV stroke volume-(LAmax-LAmin)])left atrial function index(LAFI)=(LAEF*LVOT-TVI)/LAVImax(LVOT-TVI:time velocity integral of left ventricular outflow tract)P-MV:the pulse-wave Doppler sample was placed on the mitral inflow tract in the apical 4-chamber view.The P-MV was defined as the time interval between the onset of P-wave in lead II on the ECG to the peak A wave of mitral valve PW.PA-TDI: to assess the PA-TDI,we placed the cursor on the LA lateral wall just above the mitral annulus and measure the time interval between the onset of the P-wave in lead II on the ECG to the peak a'-wave.Results1.For patients with paroxysmal atrial fibrillation,the heart rate was significantly increased after the stand-alone thoracoscopic minimal invasive atrial fibrillation ablation plus LAA resection.The left atrial function index(LAFI)decreased one week after the surgery,and maintained three months after the surgery.Although the operation reduced the left atrial reservoir function slightly,there was no significantly statistical difference among pre-operation,one week post-operation and three month postoperation.Left atrial conduit function was not affect by the surgery.The most significant effect of the surgery was left atrial systolic function.It decreased significantly one week after the operation,and gradually recovered to the preoperative level three months after the operation.2.For patients with non-paroxysmal atrial fibrillation,left atrial size,including left atrial diameter and left atrial volume,LAFI,left atrial ejection fraction(LAEF)and left atrial extension index(LAEI)were related to the success rate of the surgery.The presence of conduit function also facilitated the recovery of sinus rhythm after the surgery.In addition,hypertrophic cardiomyopathy was a factor to the failure of the surgery.In patients with non-paroxysmal atrial fibrillation,there was no significant changes in left atrial size,left atrial function,left ventricular systolic and diastolic function if the sinus rhythm could not be restored after the surgery.The patients of non-paroxysmal atrial fibrillation,who restored to sinus rhythm after the surgery,the minimum volume of left atrium was significantly decreased and the left atrial systolic function appears.Total atrial conduction time(TACT),including P-MV and PA-TDI and atrial mechanical contraction were in an abnormal state one week after surgery and gradually recover three months after the surgery.Neither paroxysmal nor non-paroxysmal atrial fibrillation was associated with recurrence of thromboembolism or stroke during one-year follow-up.ConclusionIn patients with paroxysmal atrial fibrillation,stand-alone minimal invasive radiofrequency ablation plus LAA resection had a significant effect on the electromechanical coupling of the left atrial systolic function.The left atrial systolic function decreased significantly one week after the operation.All patients had been resection of LAA and anticoagulant drugs were discontinued.In the one-year followup,no patients showed thromboembolism or stoke.It suggested that the occurrence of atrial fibrillation could be reduced after left atrial appendage resection.Preoperative parameters of patients with non-paroxysmal atrial fibrillation,including left atrial diameter,left atrial volume,left atrial function index and conduit function,could provide certain reference information for the success rate of the standalone minimal invasive radiofrequency ablation plus left atrial appendage resection.Hypertrophic cardiomyopathy was also a factor of the failure of the surgery.Non-paroxysmal atrial fibrillation those could not restored to sinus rhythm after the surgery,their left atrial function,left ventricular systolic function and diastolic function had no changed.Anticoagulant drugs had been stopped after left appendage resection.And no patient had recurrence thromboembolism or stroke.This phenomenon also suggested that left atrial resection could reduce the events of atrial fibrillation.Those non-paroxysmal atrial fibrillation patients restored to sinus rhythm after the surgery,their LAEF and LAEI,reflecting the reservoir function of the left atrium,as well as LAFI,were significantly increased due to the decrease of the minimum volume of the left atrium.It suggested that the left atrial minimum volumes was associated with the prognosis of atrial fibrillation after the surgery.Once the atrial fibrillation patients restored to sinus rhythm,left atrial systolic function appeared,which was manifested by the active systolic ability of the left atrium.However,the electromechanical coupling systolic parameters that caused the active atrial contraction did not completely recover within one week after the surgery.The reason of this phenomenon was that the atrium stunning.And this function of left atrium slowly recovered within three months after the surgery.This indicated that the atrial fibrillation was developing in a good direction after the surgery.It suggested that if electromechanical coupling could be recovered gradually after the surgery in patients with non-paroxysmal atrial fibrillation.It also is a good indication of the prognosis of atrial fibrillation... |
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