2.3. Echocardiographic assessment

Echocardiography was performed in the harmonic imaging mode using a 3-MHz transducer in a commercial ultrasound system (Vivid-7; General Electric-Vingmed, Milwaukee, WI). LV internal dimensions, LV wall thickness, and LV ejection fraction (LVEF; measured using the biplane modified Simpson rule) were measured following the recommendations of the American Society of Echocardiography (ASE).^[9]

LV mass was calculated following ASE recommendations as LV mass = 0.8 × {1.04 × [(PWTd + VSTd + LVIDd)³ − (LVIDd)³]} + 0.6 g, where PWTd and SWTd were the posterior and septal wall thickness at end diastole, respectively, and LVIDd was the M-mode LV dimension with the short axis view at end-diastole.^[10] Allometric height-based adjustments were used to express the LV mass index per height^2.7, which provides a more accurate estimation of LV hypertrophy and other pathological changes in heart structure, particularly in obese subjects.^[11]

Relative wall thickness (RWT), which increases with concentric remodeling and concentric hypertrophy, was calculated as RWT = 2 × PWTd/LVIDd. The LA dimension was measured by 2-dimensional-guided M-mode echocardiography using the parasternal short-axis view at the base of the heart. Three LA dimensions were used to calculate the LA volume as an ellipse using the formula LA volume = (π/6) × (SA₁ × SA₂ × LA), where SA₁ is the M-mode LA dimension, and SA₂ and LA are measurements of the short- and long-axis, respectively, in the apical 4-chamber view at ventricular end-systole. The LA volume index was calculated by dividing LA volume by body surface area.^[9]

Transmitral inflow velocities were measured using pulsed-wave Doppler in the apical 4-chamber view with the sample volume placed at the mitral valve leaflet tips.^[12] Measurements of the transmitral early diastolic (E wave) and atrial (A wave) velocities were used to calculate the E/A ratio and E wave deceleration time. Tissue Doppler imaging in the apical 4-chamber view was used to measure LV myocardial velocities, with the sample volume placed at the septal mitral annulus. The early (E′) and late diastolic velocities (A′) were measured, and the E/E′ ratio was calculated.^[12,13]

Cutoffs for defining abnormal chamber size and function followed ASE recommendations.^[9,12] LV hypertrophy was defined as a LV mass >48 g/m^2.7, LA enlargement was defined as LA volume >58 mL, and LV enlargement was defined as a LV end-diastolic dimension >5.9 cm. Diastolic dysfunction was graded on a 4-point ordinal scale: normal; mild diastolic dysfunction, defined as abnormal relaxation without increased LV end-diastolic filling pressure (E/A ratio <0.75); moderate or “pseudonormal” diastolic dysfunction, defined as abnormal relaxation with increased LV end-diastolic filling pressure (E/A ratio 0.75–1.5, deceleration time >140 ms, and 2 other Doppler indices of elevated LV end-diastolic filling pressure); or severe diastolic dysfunction, defined as advanced reduction in compliance with restrictive filling (E/A ratio >1.5, deceleration time <140 ms, and Doppler indices of elevated LV end-diastolic filling pressure).