CARDIOVASCULAR MEDICINE

Effects of ventricular rate and regularity on the velocity and magnitude of left atrial appendage flow in atrial fibrillation

O A Obel, L Luddington, N Maarouf, K Aytemir, C Ekwall, M Malik and A J Camm

Department of Cardiological Sciences, St Georges Hospital Medical School, London, UK

Correspondence to:
Correspondence to:
Dr Owen A Obel
Department of Cardiology 111A, Dallas VA Health-center, 4500 South Lancaster Road, Dallas, TX 75216, USA; owen.obel{at}utsouthwestern.edu

Objective: To prospectively determine whether ventricular rate and regularity are significant determinants of the velocity and magnitude of left atrial appendage (LAA) flow.

Design and patients: 12 patients with atrial fibrillation (AF), high degree atrioventricular block, and indwelling permanent pacemakers were studied.

Setting: Cardiology department of a tertiary referral centre.

Interventions: Pacing was triggered by an external programmable transcutaneous device. Patients were paced at 60, 120, and 150 beats/min in both regular and irregular rhythm. LAA flow velocity and magnitude were assessed with transoesophageal Doppler echocardiography.

Main outcome measures: Peak and mean LAA inflow and outflow velocity, and time-velocity interval (TVI) of LAA flow.

Results: Increasing ventricular rate was associated with significantly lower peak inflow (p < 0.01), peak outflow (p < 0.05), mean inflow (p < 0.01), and mean outflow (p < 0.05) velocities and with a lower TVI of LAA filling and emptying velocities (p < 0.01). This effect was noted at rates of 60 beats/min compared with both 120 and 150 beats/min. At a pacing rate of 120 beats/min there was a significantly higher total TVI when pacing at a regular than at an irregular rhythm (40.16 (14.6) cm v 30.74 (10.9) cm, p < 0.05).

Conclusions: In this study, LAA filling velocities in patients in AF were significantly influenced by paced ventricular rate and to a much lesser extent ventricular rhythm. These results suggest that rapid ventricular rates may predispose to stasis in the LAA in AF.

Abbreviations: AF, atrial fibrillation; AV, atrioventricular; LAA, left atrial appendage; LV, left ventricular; SEC, spontaneous echo contrast; TVI, time-velocity interval

Keywords: atrial fibrillation; ventricular rate; ventricular rhythm; left atrial appendage; thromboembolism

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