Atrial Strain and Strain Rate in a General Population: Do These Measures
Improve the Assessment of Elevated NT-proBNP Levels?
Abstract
Background Noninvasive assessment of elevated filling pressure in the
left ventricle (LV) remains an unresolved problem. Of the many
echocardiographic parameters used to evaluate diastolic pressure, the
left atrial strain and strain rate (LA S/SR) have shown promise in
clinical settings. However, only a few previous studies have evaluated
LA S/SR in larger populations. Methods A total of 2033 participants from
Norwegian (Tromsø 7) and Russian (Know Your Heart) population studies,
equally distributed by age and sex, underwent echocardiography,
including atrial and ventricular S/SR and NT-proBNP measurements. Of
these, 1069 were identified as healthy (without hypertension, atrial
fibrillation (AF), or structural cardiac disease) and were used to
define the age- and sex-adjusted normal ranges of LA S/SR. Furthermore,
the total study population was divided into groups according to ejection
fraction (EF) ≥50%, EF <50%, and AF. In each group, uni- and
multiple regression and receiver operating characteristic curve analyses
were performed to test LA and LV functional parameters as potential
indicators of NT-proBNP levels above 250 ng/ml. Results The mean LA S/SR
values in this study were higher than those in previous large studies,
whereas the lower references were comparable. In normal hearts, atrial
total strain (ATS) and mitral valve E deceleration time (MV DT) were
independent factors indicating elevated NT-proBNP levels, whereas in
hearts with reduced EFs, the independent indicators were peak atrial
contraction strain (PACS) and LV stroke volume. The areas under the
curve for these significant indicators to discriminate elevated
NT-proBNP levels were 0.639 (95% confidence interval (CI): 0.577-0.701)
for normal EF and 0.805 (CI: 0.675-0.935) for reduced EF. Conclusion The
results confirm good intrastudy reproducibility, with mean values in the
upper range of previous meta-analyses. In the future automated
border-detection algorithms may be able to generate highly reproducible
normal values. Furthermore, the study showed atrial S/SR as an
additional indicator of elevated NT-proBNP levels in the general
population, demonstrating the incremental value of both ATS and PACS in
addition to conventional and ventricular strain echocardiography. Thus,
the LA S/SR may be regarded as an important addition to the
multiparametric approach used for evaluating LV filling.