Chest
Volume 107, Issue 3, March 1995, Pages 690-696
Journal home page for Chest

Clinical Investigations: Cardiology: Articles
Left Atrial Appendage Contractile Function in Atrial Fibrillation: Influence of Heart Rate and Cardioversion to Sinus Rhythm

https://doi.org/10.1378/chest.107.3.690Get rights and content

Background

A high incidence of embolic phenomena is associated with atrial fibrillation (AF) and the left atrial appendage (LAA) is frequently the source of the emboli. Thrombus formation may be due to stasis within the fibrillating and inadequately emptying LAA. Because LAA emptying in AF may be the result of mechanical compression by the adjacent left ventricle, it is possible that left ventricular diastolic filling duration will importantly influence passive emptying of the LAA. We hypothesized that the magnitude of emptying of the LAA in AF is related to the duration of left ventricular diastolic filling which is determined by the ventricular response rate in AF.

Objective

The objective of our study was to determine the relationship of ventricular response rate in AF to LAA emptying and to assess the influence of sinus rhythm and heart rate on LAA emptying immediately after direct current cardioversion to sinus rhythm.

Methods

To study this, we used transesophageal echocardiography to measure LAA ejection fraction ([LAAmax—LAAmin]/LAAmax×100%) and evaluated its relationship to left ventricular response rate (VRR) in 26 patients with AF (mean age, 65 ± 7 [1 SD] years).

Results

There was a strong inverse relationship between LAA ejection fraction and VRR in AF (r= −0.73; p<0.001). LAA ejection fraction during AF was 26 ± 10%, and immediately after successful cardioversion, it increased to 46 ± 12% (p<0.001). However, during sinus rhythm there was no relationship between LAA ejection fraction and VRR (r=0.06; p=NS) in the subgroup of patients who were successfully converted to sinus rhythm. There were poor relationships between LAA ejection fraction and peak transmitral flow velocity (r=–0.41; p=NS) or pulmonary venous flow velocity (r=–0.03; p=NS) in AF.

Conclusion

These results indicate that the magnitude of LAA emptying in AF is strongly and inversely influenced by ventricular rate. Direct current cardioversion to sinus rhythm is associated with an increase in the magnitude of LAA emptying that is not influenced by heart rate. The magnitude of LAA emptying may be an important factor in the formation of thromboemboli in AF. The extent to which controlling the VRR in chronic AF will prevent stasis and LAA thrombus formation remains to be determined.

Section snippets

Patient Population

The study group consisted of 26 patients with chronic AF scheduled for elective direct current electrical cardioversion. The mean age was 65 ± 7 years (range, 50 to 79 years) and duration of AF was 28 ± 22 months (range, 1 week to 7 years). The underlying cardiac disease was dilated cardiomyopathy in four patients, coronary artery disease in five patients, and mitral stenosis in two patients. Hypertension, COPD and diabetes were documented in 10, 3, and 4 patients, respectively. Table 1 lists

Left Atrial Appendage Ejection Fraction vs Heart Rate

During AF in the subset of patients with available transesophageal echocardiographic data both immediately before and immediately after cardioversion, mean heart rate (VRR) was 103 ± 31 beats per minute during AF, and mean LAA ejection fraction was 26 ± 10%. The LAA appeared akinetic with poor to absent excursion of its lateral wall. The LAA ejection fraction during AF did not correlate with either left atrial chamber size (r=–0.014; p=NS) or with the duration of AF (r=–0.04; p=NS). Table 2 is

Discussion

The major findings of our study are twofold: (1) LAA emptying is strongly and inversely related to the VRR during AF but is not related to heart rate following direct current cardioversion to sinus rhythm, and (2) LAA emptying increases significantly immediately after direct current cardioversion from AF to sinus rhythm.

Summary

This study offers evidence that during AF the magnitude of LAA emptying is inversely related to the VRR and that, immediately after direct current cardioversion to sinus rhythm, appendage emptying increases markedly and is not dependent on heart rate. These results support our hypothesis that LAA emptying in AF is dependent on the diastolic volume of the left ventricle which is determined by the VRR. Our data can be taken further to indicate that the increase in LAA emptying immediately after

ACKNOWLEDGMENTS

We thank James A. Brownie from Medical Media for assistance with graphics, Dorothy Robinson for assistance with data management, and Michelle Rene Martin for expert assistance in the preparation of the manuscript.

References (17)

There are more references available in the full text version of this article.

Cited by (28)

  • Thoracoscopic Left Atrial Appendage Clipping: A Multicenter Cohort Analysis

    2018, JACC: Clinical Electrophysiology
    Citation Excerpt :

    Stroke prevention is a cornerstone of AF treatment. The LAA is the main source of thromboembolism in AF patients because of blood stasis and coagulation, thus fulfilling the main conditions of Virchow’s triad (14–18). Oral anticoagulation therapy is the mainstay of stroke prevention in AF, but other strategies are now available and can complement interventional approaches to rhythm control.

  • Doppler echocardiographic assessment of left atrial appendage flow velocities in normal cats

    2005, Journal of Veterinary Cardiology
    Citation Excerpt :

    In a study of 46 healthy subjects,18 four distinct flow waves were found in 36 (78%), triphasic flow was reported in six (13%), and biphasic flow in four (9%). The differences in the distribution of flow patterns between our findings and the aforementioned study may be explained in part by the different methods used with TEE being the most sensitive technique of recording LAA flow35 and differences in heart rate and PR interval between cats and man.37 In other human studies, however, only two main flow waves were described in the majority of patients – LAA emptying and filling waves – which is in agreement with our observations.17,38

  • Obliteration of the left atrial appendage for prevention of thromboembolism

    2003, Journal of the American College of Cardiology
  • Does acute-phase beta blockade reduce left atrial appendage function in patients with chronic nonvalvular atrial fibrillation?

    2001, Journal of the American Society of Echocardiography
    Citation Excerpt :

    Because atrial myocardium contains both beta1 and beta2 adrenoceptors,14 it is plausible that beta-blockers may acutely impair LAA function in patients with chronic AF. Previous clinical studies have shown that the LAA emptying velocity is inversely related to heart rate during AF and sinus rhythm.15,16 If this is true, reduction in heart rate caused by beta blockade will result in increased LAA emptying velocity in patients with AF; however, our study demonstrated that acute administration of metoprolol decreased LAA emptying velocities, despite the reduction in heart rate.

  • A prospective, randomized controlled trial comparing the efficacy and safety of sotalol, amiodarone, and digoxin for the reversion of new-onset atrial fibrillation

    2000, Annals of Emergency Medicine
    Citation Excerpt :

    The ineffective atrial contractions in AF reduce effective cardiac output, especially during exercise, and substantially increase the risk of stroke as a result of the formation and embolization of atrial thrombus.3 Sustained AF with rapid ventricular rate may also result in reversible tachycardia-induced left ventricular dysfunction,4,5 further increasing left atrial stasis.6 AF increases the risk of ischemic stroke sixfold to approximately 5% per year,7 and embolic strokes related to AF are usually large with death or severe neurologic deficit in 50% to 70% of cases.8

View all citing articles on Scopus

This study was supported in part by the funds from Veterans Affairs Research Service.

View full text