The effect of transient balloon occlusion of the mitral valve on left atrial appendage blood flow velocity and spontaneous echo contrast: a comparison in sinus rhythm and atrial fibrillation patients

Abstract

Objective: To investigate the relationship between spontaneous echo contrast (SEC) and left atrial appendage (LAA) blood flow velocity using transesophageal echocardiography (TEE) during percutaneous balloon mitral valvotomy (PBMV) in patients with atrial fibrillation and sinus rhythm.

Methods: Thirty-five patients (21 in sinus rhythm and 14 in atrial fibrillation) with rheumatic mitral stenosis underwent PBMV with intraoperative transesophageal echocardiography monitoring. We measured LAA blood flow velocities and observed the left atrium for various grades of SEC (from 0 = none to 4 = severe), before and after each balloon inflation.

Results: Left atrial appendage maximal emptying velocity (LAA MEV) was reduced from 35 +/- 14 cm/s to 6 +/- 2 cm/s at peak balloon inflation and increased to 40 +/- 16 cm/s after balloon deflation. Comparison of the values before balloon inflation and after balloon deflation showed that LAA velocities were significantly lower (P < 0.001). During balloon inflation, both maximal emptying velocity (MEV) and maximal filling velocity (MFV) were significantly decreased, compared to those before inflation and after balloon deflation (P < 0.01). And both MEV and MFV were significantly higher after balloon deflation relative to those before balloon inflation. Patients with atrial fibrillation had significantly lower MEV and MFV before and during balloon inflation and after balloon deflation than patients with sinus rhythm. At peak balloon inflation, new or increased SEC grades were observed during 54 of 61 (88%) inflations and unchanged during 7 (12%) inflations. SEC grades were reduced after 55 balloon deflations (90%), completely disappeared after 18 deflations (30%) and remained unchanged after 6 deflations (10%). At peak balloon inflation, left atrium spontaneous echo contrast (LASEC) grade 4 was observed during 14 of 27 (93%) inflations in the atrial fibrillation patients, significantly higher than in patients with sinus rhythm (8 of 34, 24%; P < 0.05). LASEC completely disappeared after 16 of 34 deflations (47%) in the patients with sinus rhythm, significantly higher than in the atrial fibrillation patients (2 of 27 deflations; P < 0.01). The mean time to achieve maximal SEC grade (2.5 +/- 1.2 s) correlated with the mean time to trough LAA velocities (2.3 +/- 1.1 s) after balloon inflation. Both the time to lowest LAA velocity and the time to highest LASEC were significantly longer in the patients with sinus rhythm than in the atrial fibrillation patients (2.6 +/- 1.1 s vs 1.7 +/- 1.0 s, P < 0.05 and 2.8 +/- 1.4 s vs 1.9 +/- 1.3 s, P < 0.05, respectively). Upon deflation, the mean time to lowest SEC grade (2.9 +/- 1.8 s) correlated with the mean time to achieve maximal LAA velocities (2.7 +/- 1.6 s). Both intervals are significantly shorter in the patients with sinus rhythm than in the atrial fibrillation patients (2.0 +/- 1.6 s vs 3.5 +/- 1.5 s, P < 0.01 and 2.2 +/- 1.7 s vs 3.6 +/- 1.6 s, P < 0.05).

Conclusion: Reducing the blood flow velocity in the human left atrium by balloon occlusion of the mitral valve may enhance SEC, whereas restoring blood flow after balloon deflation would cause enhanced echogenic blood to disappear or decrease in both groups of patients. Patients with atrial fibrillation demonstrate more severe blood stagnation of the left atrial body and appendage during transient balloon inflation at mitral valve orifice and slower recovery from the stagnation, decreasing to a lesser extent after balloon deflation, when compared to patients with sinus rhythm.