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Heart rate control is associated with improved left atrial appendage function: a transthoracic echocardiographic study in patients with atrial fibrillation
  1. A Kiotsekoglou,
  2. A Younis,
  3. JC Moggridge,
  4. A Kourliouros,
  5. K Dougal,
  6. M Bizrah,
  7. A Bajpai,
  8. M Govindan,
  9. AJ Camm
  1. St George’s, University of London, London, UK

Abstract

Introduction In atrial fibrillation (AF) when coordinated atrial contraction is absent, the function of the left atrial appendage (LAA) is impaired thus increasing the risk of thrombi formation within its cavity. The close position of LAA to the left ventricular lateral wall and its forward blood flow fixed to early diastole may influence LAA emptying and filling. LAA function can accurately be assessed using transoesophageal echocardiography. However, in cases with atrial dilatation the junction between the LAA and left atrium can be visualised on transthoracic echocardiography (TTE). This study aimed to investigate the relationship between left ventricular function and LAA emptying using TTE in patients with AF.

Methods Forty AF patients, 25 men (mean age 71 ± 10 years) with the left atrium–LAA junction visualised on TTE were examined. Mitral annular motion was assessed from the lateral left ventricular wall using M-mode and tissue Doppler imaging (TDI). Motion of the left atrium area adjacent to the lateral mitral annular region was measured by placing an M-mode sounding beam in the long-axis across the left atrium–LAA junction. Measurements were made 60 ms after the beginning of the QRS to the first peak of the mitral annular and left atrium–LAA junction waveforms. Left atrium–LAA junction motion was also calculated in early diastole (fig 1). The ejection fraction and left atrium expansion index were calculated by Simpson’s biplane method and the left atrium expansion index formula  =  (max volume − min volume)/min volume × 100, respectively. All measurements were obtained from beats following a pair of similar preceding cardiac cycles.

Results The study patients were divided arbitrarily into three groups on the basis of their heart rate: group 1, <75 bpm (N  =  18); group 2, 76–100 bmp (N  =  12); and group 3, >100 bpm (N  =  10). Ejection fraction, M-mode and TDI lateral mitral annular motion measurements were significantly reduced in group 3 when compared with the other groups with slower heart rates (p<0.001). The left atrium expansion index and systolic M-mode left atrium–LAA junction motion measurements were also significantly reduced in group 3 (p<0.001). The left atrium–LAA junction measurements in early diastole showed a significant reduction in patients in group 3 when compared with the other groups (p<0.001). Mitral valve deceleration time and isovolumic relaxation time were also significantly reduced in group 3 (p<0.001), whereas mitral valve E-wave velocity values showed no differences between the groups. Diastolic left atrium–LAA junction measurements were correlated with the ejection fraction (r  =  0.45, p = 0.003), deceleration time (r  =  0.47, p = 0.002), TDI diastolic velocities (r  =  0.54, p<0.001) and left atrium expansion index (r  =  0.60. p<0.001).

Conclusion Our findings suggest that LAA function may be significantly affected by left ventricular and left atrial function. In this study, a slower heart rate was associated with a wider left atrium–LAA junction distance in diastole, indicating preserved emptying. Heart rate control in AF patients may reduce LAA stasis and result in reduced thrombus formation thus decreasing the risk of thromboembolic events.

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