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Role of Left Atrial Appendage in Left Atrial Reservoir Function as Evaluated by Left Atrial Appendage Clamping During Cardiac Surgery

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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.

Section snippets

Study Subjects:

Subjects consisted of 8 patients who had undergone coronary artery bypass graft (CABG) surgery (6 men and 2 women, mean age 63 ± 7 years) and 7 patients with mitral regurgitation (MR) due to rupture of the chordae tendineae, and followed by mitral valve repair or prosthetic valve replacement (5 men and 2 women, mean age 65 ± 8 years). All patients were in normal sinus rhythm. The patients in the CABG group included 5 with 2-vessel disease and 3 with multivessel disease. None had MR more than

Baseline Characteristics Before LAA Clamping:

There were no significant differences in age, heart rate, systolic systemic blood pressure, or left ventricular percent ejection fraction (61 ± 8% vs 63 ± 6%) between the MR and CABG groups. The mean LA pressure was significantly higher in the MR group than in the CABG group. The maximal LAA area (4.0 ± 0.8 vs 1.9 ± 0.2 cm2, p <0.01) and, LA dimension and left ventricular end-diastolic dimension (5.4 ± 0.4 vs 4.8 ± 0.4 cm, p <0.05) were significantly greater in the MR group than in the CABG

Discussion

The LAA has a blind pouch shape, and its orifice opens to the LA main chamber between the pulmonary veins and the left ventricle. Because the LAA volume normally is about 30% of that of the entire LA volume,[10]the LAA is considered to play an important role in hemodynamic abnormalities between the left atrium and left ventricle. However, much attention has been given to the LAA because of its high susceptibility to blood stagnation and thrombosis, and as a source of systemic embolism due to

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