Improving the diagnosis of heart failure in patients with atrial fibrillation

Objective To improve the echocardiographic assessment of heart failure in patients with atrial fibrillation (AF) by comparing conventional averaging of consecutive beats with an index-beat approach, whereby measurements are taken after two cycles with similar R-R interval. Methods Transthoracic echocardiography was performed using a standardised and blinded protocol in patients enrolled in the RATE-AF (RAte control Therapy Evaluation in permanent Atrial Fibrillation) randomised trial. We compared reproducibility of the index-beat and conventional consecutive-beat methods to calculate left ventricular ejection fraction (LVEF), global longitudinal strain (GLS) and E/e’ (mitral E wave max/average diastolic tissue Doppler velocity), and assessed intraoperator/interoperator variability, time efficiency and validity against natriuretic peptides. Results 160 patients were included, 46% of whom were women, with a median age of 75 years (IQR 69–82) and a median heart rate of 100 beats per minute (IQR 86–112). The index-beat had the lowest within-beat coefficient of variation for LVEF (32%, vs 51% for 5 consecutive beats and 53% for 10 consecutive beats), GLS (26%, vs 43% and 42%) and E/e’ (25%, vs 41% and 41%). Intraoperator (n=50) and interoperator (n=18) reproducibility were both superior for index-beats and this method was quicker to perform (p<0.001): 35.4 s to measure E/e’ (95% CI 33.1 to 37.8) compared with 44.7 s for 5-beat (95% CI 41.8 to 47.5) and 98.1 s for 10-beat (95% CI 91.7 to 104.4) analyses. Using a single index-beat did not compromise the association of LVEF, GLS or E/e’ with natriuretic peptide levels. Conclusions Compared with averaging of multiple beats in patients with AF, the index-beat approach improves reproducibility and saves time without a negative impact on validity, potentially improving the diagnosis and classification of heart failure in patients with AF.


About atrial fibrillation (AF)
AF is a common heart condition that leads to an irregular and often rapid heart rate, which can make patients feel unwell and have more admissions to hospital. AF also causes 1 in 4 strokes and can reduce heart function over time resulting in a condition called heart failure.

What was the purpose of this study?
The assessment of heart function plays an important role in deciding what treatments a patient with AF should receive. To assess the function of the heart, patients are referred by their doctor to have an echocardiogram, which is an ultrasound scan of their heart. During the scan, multiple measurements are taken to determine how well the heart is pumping and relaxing. In patients with AF this is challenging because the heart rhythm is irregular causing measurements to vary between different heartbeats. Normally we average a number of heart beats, but this is time-consuming and may not be accurate in patients with AF. In this study we compared the routine method of averaging measurements with a new method, based on taking measurements after heartbeats of similar length (called the indexbeat method). This was carried out in patients taking part in a study to find out which heart rate control medication is better for patients, called the RATE-AF trial. The patients were aged 60 years and over with constant (permanent) AF who also had symptoms suggestive of heart strain or failure of the heart pump.

Summary of the study findings
Using the index-beat method caused less variability in measurements that assess how well the heart is pumping and relaxing. It also reduced the time taken to perform the scan when compared to averaging multiple beats. The new approach, although quicker, did not compromise how the measurements related to standard blood tests of heart function.

Implications for patients
It is essential that your heart function can be accurately assessed so that your doctor can prescribe the correct treatments for AF and heart failure. The index-beat method has been shown to improve the reliability of assessing heart function in AF patients and reduce the time taken for the heart scan. Its use in clinical practice could allow doctors to provide better treatment for AF patients, improving quality of life and preventing any worsening in health status.

Patient support
Patient information from the British Heart Foundation: https://www.bhf.org.uk/hearthealth/conditions/atrial-fibrillation. Education and support groups for patients and carers from the Heart Rhythm Alliance: https://www.heartrhythmalliance.org/. Free smartphone and tablet apps for healthcare professionals and patients with AF from the European Society of Cardiology: www.escardio.org/af-apps.

Supplementary Table 4. Intra and inter-operator reproducibility of GLS.
Intra and inter-operator reproducibility of GLS when using a single index-beat verses the average of 3, 5 and 10 beats. Displayed as Bland and Altman analysis (bias and limits of agreement) and the intra-class correlation coefficient derived from the mixed effects multi-level linear regression model adjusting for the patient and measurement time.

Reproducibility
Single index beat 3 consecutive beats 5 consecutive beats 10 consecutive beats

Intra-operator (n=50)
Bias (   Univariate linear regression analysis to show the correlation between LVEF Simpson's biplane, GLS and E/e' measured using a single index-beat verses the average of 3, 5 and 10 consecutive beats. The beta coefficient describes the change in echocardiographic parameter for a single unit increase in NT-proBNP. A test dependent correlation coefficient (CorCor) was used to assess the difference in correlation coefficient when measuring on a single index beat verses averaging consecutive beats.

Supplementary Figure 2. Bland and Altman plots to show GLS and E/e' intra-operator reproducibility in 50 patients
(A) GLS and (B) E/e' when measured by the same operator, using a single index-beat versus the average of 5 and 10 consecutive beats. E/e' = Mitral E wave max / average diastolic tissue Doppler velocity from the septal and lateral annulus; GLS = global longitudinal strain .