Author + information
- Yasir Abu-Omar, MBChB, DPhil,
- Benjamin S. Thorpe, PhD,
- Carol Freeman, MPhil,
- Christine Mills, MSc,
- Victoria E.A. Stoneman, PhD,
- Deepa Gopalan,
- Bushra Rana, MBBS,
- Tomasz J. Spyt, MD,
- Linda D. Sharples, PhD and
- Samer A.M. Nashef, MBChB, PhD∗ ()
- ↵∗Papworth Hospital, Papworth Everard, Cambridge, Cambridgeshire CB23 3RE, United Kingdom
Atrial fibrillation (AF), the commonest dysrhythmia, affects nearly 4.5 million people in Europe and 2.2 million in the United States. Prevalence increases with age (4% at age >60 years and 9% at age >80 years), and its effect on quality of life and health resources is considerable. Fibrillating atria have no contractile function. The most serious complication is thromboembolic stroke (12,500 strokes are attributed to AF annually in the United Kingdom). To reduce thromboembolism, patients are anticoagulated, which increases bleeding risk. AF also exacerbates heart failure and is a rising public health burden as the population ages.
The maze procedure creates lesions in the atria to obstruct the macro–re-entry circuits essential to sustain AF. Maze is most commonly performed as an adjunct to major cardiac surgery and significantly increases 12-month freedom from AF, restoring sinus rhythm (SR) in 44% to 94% of treated patients compared with 5% to 33% of control subjects (1). Restoring SR does not guarantee return of atrial contractile function, and both thromboembolism and heart failure exacerbation are related to the loss of contractile function (2).
Studies of atrial transport after maze are limited by small samples, selection bias, and lack of matched control subjects. The HESTER (Has Electrical Sinus Translated into Effective Remodelling?) matched cohort study compared atrial transport in patients whose SR was restored by maze with those in SR before and after cardiac surgery. Maze patients were in SR at least 1 year after receiving maze for persistent longstanding AF as an adjunct to cardiac surgery. Control patients were in SR before and at least 1 year after cardiac surgery, matched 1-to-1 for time since procedure (±6 months), age (±5 years), sex, type of surgery, left ventricular function, and risk profile (logistic EuroSCORE). The aim was to assess whether the 2 cohorts had equivalent left atrial (LA) function, primarily active left atrial ejection fraction (ALAEF):
where LAVpreA = pre-A wave left atrial volume and LAVmin = minimum left atrial volume. Secondary outcomes were LA volume measurements, active and passive stroke volume, and LA ejection fraction.
LA function was evaluated by transthoracic echocardiography and multislice cardiac magnetic resonance imaging. For each modality, a single operator blinded to patient identity performed the test and interpreted the findings. A mixed effects linear regression model was fitted, including treatment and matching variables (fixed effects) and matched pairs (random effects). An unconstrained covariance model was assumed. The estimated treatment coefficient was taken as the mean ALAEF difference. In normal subjects in SR, mean ALAEF was 43 ± 18.2% (3), which could be taken as the minimum clinically important difference in ALAEF.
Between 2013 and 2015, 22 pairs were recruited and had LA functional measurements. Maze patients had lower mean ALAEF (18.4%) than control subjects (26%). One-to-one comparison shows that control subjects had higher ALAEF in all but 3 pairs (Figure 1). After adjusting for the paired design and matching variables, mean ALAEF was 8.03% lower in maze than control subjects (95% confidence interval: −12.43% to −3.62%; p = 0.0015).
Patients with chronic AF may have persistent LA dysfunction even after restoration of SR by ablation. Buber et al. (2) reported that absence of LA contraction, despite SR restoration, is associated with a significant increase in the risk of thromboembolic stroke after maze. Global and regional atrial dysfunction may be the result of a combination of injury from the ablation process and pre-existing disease (2). The 2 adverse features of asymptomatic AF, thromboembolism and effect on cardiac function, are both directly related to atrial function. Restoring SR without restoring function is unlikely to be of clinical benefit. The HESTER study provides evidence that function is indeed restored after adjunct maze, with potential clinical benefits in reducing thromboembolic and heart failure risk. Determining whether patients can safely stop taking anticoagulants after SR is restored by a maze procedure requires long-term follow-up and stroke surveillance beyond the HESTER study. The varying rates of LA functional recovery after maze means that it would be prudent to measure atrial function before considering anticoagulation withdrawal.
In summary, a return to SR after adjunct maze is associated with recovery of LA function but with a mean ALAEF smaller in maze patients than in control subjects. This functional recovery and the variability observed within it may have important implications for survival, heart function, and clinical decisions on long-term anticoagulation.
Please note: This work has received funding from the National Institute for Health Research Health Technology Assessment Programme. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
- Buber J.,
- Luria D.,
- Sternik L.,
- et al.
- Anwar A.M.,
- Geleijnse M.L.,
- Soliman O.I.,
- Nemes A.,
- ten Cate F.J.