Index-beat approach improves diagnosis of heart failure in AF patients

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An assessment method known as the index-beat approach could improve the diagnosis of heart failure in patients with atrial fibrillation (AF), authors of a study published online in BMJ: Heart have found.

Karina Bunting (Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK) details the approach on behalf of the Rate control Therapy Evaluation in permanent Atrial Fibrillation (RATE-AF) trial group.

Compared to a conventional method of echocardiographic assessment, which involves averaging of three beats (clinical routine) and five beats and 10 beats (as recommended in guidelines), an index-beat approach sees measurements taken after two cycles with similar R-R interval. The index-beat method takes into account time-dependent processes involved in contractility, Bunting writes.

The study aimed to compare the two approaches, and to ascertain whether this “more physiological approach” could improve the assessment of heart failure in patients with AF. Researchers hypothesised that the index-beat method would be more reproducible and time-efficient, facilitating better management of patients with AF and heart failure.

Taking patients enrolled in the RATE-AF randomised trial, the study team 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.

In total 160 patients were included in the study, 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).

Bunting et al report that the index-beat had the lowest within-beat coefficient of variation for LVEF (32%, vs 51% for five 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, the study team notes, 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 five-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, the study team adds.

Considering these findings, Bunting and colleagues conclude: “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.”


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