| OBJECTIVE: Atrial fibrillation (AF) is the most common sustained cardiac dysrhythmia requiring therapy. It occurs in approximately 4% of the general adult population. In our country, AF is mostly caused by rheumatic heart valve disease , especially with mitral valve stenosis. Chronic AF is associated with complications including heart failure, stroke, and exercise intolerance. When it is present many prognostic and therapeutic implications exist as overall morbidity and mortality increase. Soon after the onset of AF, atrial contractile function decrease, electrical and mechanical changes occur, referred to as remodeling. Experimental and clinical investigations suggested that intracellular calcium overload contributes to AF-induced electrical and structural remodeling. These adverse changes, including alterations in how rapidly atrial tissues recover excitability and enlargement of the atria, are believed to facilitate the development and maintenance of AF, hence the concept"AF begets AF". According to the theory the cardioversion therapy is necessary. Nonpharmacologic therapies for the treatment of AF, namely, catheter ablation, cardiac pacing, internal defibrillation, and dysrhythmia surgery are playing an increasingly important role in the overall management of AF. The Cox maze procedure has shown to be effective in treating atrial fibrillation. Radiofrequency ablation, with a similar objective, has been proved to be effective as an adjunct to conventional cardiac surgery. These therapies for AF, offering the promise of prevention and cure of AF, potential elimination from the sequelae of AF, and significant improvements in quality of life, are increasingly becoming more frequent in clinical practice. But none of the therapies can eradicate AF. Mechanic stress and the corresponding cell signaltransduction pathway is the mostly appreciated cardiac investigation direction at present, which is thought to be in the center of the pathogenesis of heart disease. The aim of the first and second part of this article is to evaluate left atrial (LA) hydrodynamics of patients suffred atrial fibrillation with rheumatic mitral valve stenosis (MS) in order to provide useful information in the clinical practice of searching for and selecting effective prognosis.At present, transthoracic echocardiography (TTE) and magnetic resonance imaging (MRI) are both useful uninjured methods for studying heart disease, while TTE has been the standard method for studying heart valve disease. For recent years, many new techniques, such as Acoustic quantification (AQ), have been developed. AQ, an automated border detection technique (ABD), provides on-line continuous cardiac chamber area or volume over time and has been used extensively to study the left ventricle. The objective of third part of this article is to evaluate the value of the AQ in studying the LA contractile function. PART ONE The difference of LA hydrodynamics between the controll and the patients with MS with atrial fibrillation (AF) or with sinus rhythm (SR). METHODS:105 patients with MS and 50 controlls were studied by TTE. The patients were divided into 2 groups (AF and SR group).Trans-mitral peak pressure gradent (PGmax), mean pressure gradent (mPG), PHT, VTI and effective orifice area, (EOA) were measured by pulse and consistant wave Doppler technique. Maximum left atrial area (LAAmax), minumum left atrial volume (LAVmax), minumum left atrial area (LAAmin), minumum left atrial volume (LAVmin) were measured by two-dimension echocardiography (2DE) and left atria ejectional fraction (LAEF), and left atrial stress (LAS) were calculated according to LAS=PGmax/4LAAmax.Left ventricular ejectional fraction (LVEF) and left ventricular fraction shortening (LVFS) were measured by M-mode echocardiography.RESULTS:LAAmax, LAVmax, LAAmin and LAVmin in group AF were higher than group SR, while the PGmax, mPG, PHT, VTI and EOA were similar in two groups. LAAmax, LAVmax, LAAmin, LAVmin, PGmax, mPG, PHT, and VTI in patients were all higher than in controll, while EOA in patients were lower than in controll. LAEF in group AF were lower than controll while LAEF in group SR were similar to controll. LAS in patients were higher than in controll, while group AF lower than group SR. LVEF and LVFS were similar in three groups. CONCLUSIONS:LAS plays a key role in the progress of AF, while the increase of LAV may be an important factor in progression to permanency of AF. PART TWO The change of LA hydrodynamics of the patients with MS after the surgery of mitral valve replacement (MVR) METHODS:The subjects were 240 patients with MS and 50 controlls. The patients were divided into 6 groups (AF and SR group) according to their rhythm and the time before or after MVR separately. The subjects in the first and second group and controlls were the same as part one. The third group included 45 AF patients and the forth group included 37 SR patients, from 6 to 12 months after MVR. The fifth group included 38 AF patients and the sixth group included 15 SR patients, beyond 12 months after MVR.The parameters measured were the same as part one except for LAAmin, LAVmin and LAEF. RESULTS:LAAmax and LAVmax in AF patients were higher than SR patients, and after MVR, LAS, PGmax, mPG, PHT and VTI decreased while EOA increased. Within 1 year, the change came to a steady level and no more change occured for a long time. After MVR, the degree of change in LAS was higher in SR patients than in AF patients. While no change in LAAmax and LAVmax occured after MVR.All these parameters in patients were higher than controll.LVEF and LVFS were similar in seven groups. CONCLUSIONS:After MVR, LAS decreased while there was no change in LAV ,which suggested that the abnormal LAS may lead to the occurrence of AF, while the increase of LAV may be important in progression to permanency of AF.PART THREE AQ technique in the assessment of LA contractile function METHODS:The subjects were 38 patients with MS and 20 controlls. AQ and 2D technique were both applied to measure LAVmax, LAVmin and LAEF. RESULTS:There was a linar correlation of the parameters measured by two techniques. The correlation coefficient (r) of LAVmax, LAVmin and LAEF was 0.89,0.92 and 0.86 respectively. But ABD technique wasn't applied satisfactorily in patients after MVR and those with thrombus in left atrial. CONCLUSIONS:AQ technique can assess the change of LA contractile function as well as two-dimension technique. But in patients after MVR and those with thrombus in left atrial, ABD technique's application in the assessment of LA function may be restricted. |
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