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Role of left atrial appendage in left atrial reservoir function as evaluated by left atrial appendage clamping during
1The Second Department of Internal Medicine, School of Medicine, The University of Tokushima, Tokushima City, Japan.
Insights
The left atrial appendage (LAA) significantly contributes to left atrial (LA) reservoir function. Its clamping impacts LA flow dynamics, highlighting its crucial role in managing pressure and volume overload.
Area of Science:
- Cardiology
- Cardiac Surgery
- Echocardiography
Background:
- The left atrial appendage (LAA) is a key structure within the left atrium (LA).
- Its precise contribution to overall left atrial reservoir function remains incompletely understood.
- Assessing LAA's role in LA hemodynamics is crucial for understanding cardiac physiology.
Purpose of the Study:
- To evaluate the functional role of the LAA in left atrial reservoir function.
- To assess changes in left atrial flow dynamics following LAA clamping during cardiac surgery.
- To compare LAA function in patients undergoing coronary artery bypass grafting versus mitral valve surgery.
Main Methods:
- Intraoperative transesophageal pulsed Doppler echocardiography was used to record flow velocities.
- Measurements included transmitral, pulmonary venous, and LAA flow patterns.
- Left atrial pressure was monitored before and after LAA clamping in 15 patients.
Main Results:
- The LAA was significantly larger and had lower emptying flow velocity in mitral regurgitation patients compared to CABG patients.
- LAA clamping increased transmitral and pulmonary venous flow velocities and decreased pulmonary venous systolic flow velocity.
- Mean LA pressure and LA dimension increased, with a steeper LA pressure-volume loop slope in the MR group.
Conclusions:
- The LAA exhibits greater compliance than the main left atrial chamber.
- The LAA plays a vital role in left atrial reservoir function, particularly under conditions of pressure and/or volume overload.
- These findings have implications for understanding atrial function in various cardiac conditions.
Abstract:
We evaluated the role of left atrial appendage (LAA) in the left atrial (LA) reservoir function by assessing the changes in LA flow dynamics after LAA clamping during cardiac surgery. The subjects were 8 patients who had undergone coronary artery bypass grafting (CABG) and 7 who had undergone mitral valvular surgery due to mitral regurgitation. We recorded transmitral, pulmonary venous and LAA flow velocity patterns by intraoperative transesophageal pulsed Doppler echocardiography, monitoring LA pressure before and 5 minutes after LAA clamping. The maximal LAA area was significantly greater, and the peak late diastolic LAA emptying flow velocity was significantly lower before LAA clamping in the mitral regurgitation group than in the CABG group. In both groups, the peak early and late diastolic transmitral and pulmonary venous flow velocities significantly increased, and the peak second systolic pulmonary flow velocity significantly decreased during LAA clamping. There were no significant changes in heart rate and systemic systolic blood pressure during LAA clamping, whereas mean LA pressure and maximal LA dimension significantly increased in both the groups. The LA pressure-volume relation during ventricular systole shifted upward and to the left during LAA clamping, and the slope was steeper in the MR group than in the CABG group. We conclude that the LAA is more compliant than the LA main chamber, and plays an important role in LA reservoir function in the presence of LA pressure and/or volume overload.