P735 Septal curvature - a novel, semi-automated parameter to aid in recognition of basal septal hypertrophy in arterial hypertension
Authors: Loncaric F , Marciniak M , Fernandes J F , Gilbert A , Nunno L , Mimbrero M , Tirapu L , Sanchis L , Doltra A , Fabijanovic D , Cikes M , Lamata P , Bijnens B , Sitges M 
Published: January 2020

Abstract

Funding Acknowledgements
Horizon 2020 European Commission Project MSCA-ITN-2016 (764738), Grant from Fundacio La Marató de TV3 (040310).

Background and aim
Localized basal septal hypertrophy (BSH) is a known marker of increased afterload and localized deformation impairment, and can be seen in one-fifth of patients with arterial hypertension. Although there is variability in the classification, BSH is mainly defined from ratios between several wall thickness measurements. We hypothesize that the curvature of the septum is reflective of localized hypertrophy and will be significantly increased in patients with BSH. Speckle tracking endocardial delineations of the left ventricle (LV) can be used to quantify curvature, with the potential to create a novel, semi-automatized parameter for recognition of patients with an increased impact of afterload on cardiac structure and function.

Methods
An echocardiogram was performed on a total of 149 patients with a diagnosis of long-standing hypertension, treated with at least one antihypertensive drug and on 19 healthy age and sex-matched controls. The interventricular septum thickness was measured at basal and mid-level in the parasternal long axis (PLAX) and 4-chamber (4C) views. BSH was identified from a two-part criterion: both a positive visual assessment of an abrupt change in septal thickness seen in the 4C or PLAX views and a basal to mid-septal ratio ≥ 1.4. A dedicated software for speckle tracking was used to trace the endocardial border of the LV in 4C and 3C view. In post-analysis, we quantified the maximal curvature of the antero- and inferoseptal segments from the exported myocardial contour. Curvature, measured in m-1, was defined as the reciprocal value of the radius of the circle fitted into the curve defined by three subsequent neighboring points in the myocardial contour. Curvature was considered negative if the curve was convex with respect to the LV long-axis.

Results
Using septal wall thickness measurements, 19% (n = 28) of hypertensive patients were classified as having BSH, whereas all healthy controls had normal geometry. Basal antero- and inferoseptal wall thickness was significantly increased in the BSH group, which was coupled with regional deformation impairment (basal inferoseptum, controls vs. non-BSH vs. BSH: 16.1 ± 2.33 vs. 15.14 ± 2.8 vs. 13.02 ± 2.98 %, p &lt; 0.001). The curvature of the basal inferoseptum was significantly higher in the BSH group (controls vs. non-BSH vs BSH: -23.4 (-27.2, -10.9) vs. -28.3 (-40.2, -19.3) vs. -50.5 (-66.8, -33.9) m-1, p &lt; 0.001) (Figure 1), with the same trend seen in the basal anteroseptum. The inferoseptal curvature showed a moderately strong correlation with the inferoseptal basal-to-mid wall thickness ratio (R = 0.527, p &lt;0.001).

Conclusion
Increased septal curvature is an easily quantifiable, single-value, semi-automated parameter reflective of localized thickening that could easily be incorporated into the output of the LV speckle tracking workflow, possibly aiding in the recognition of hypertensive patients in need of a closer clinical follow-up.
Abstract P735 Figure 1