2 Materials and Methods
Eighty-one patients with AS who visited Yamaguchi University Hospital from January 2014 to July 2018 for assessment of AS severity by echocardiography with multiple approach (apical 3-chamber (3C), apical 5-chamber (5C), and right parasternal (R)) were included in this retrospective study. Echocardiographic images and data were retrieved from database and clinical chart and assessed.
These echocardiographic data were obtained by one of the following equipment: Vivid 7 (GE Healthcare), EPIC (Philips), Aplio 500 (Canon Medical Systems), or Aplio i900 (Canon Medical Systems) by standard examination technique.
Inclusion criteria were 1) patients with AS > mild, 2) LVEF > 50% and stroke volume index (SVI)> 35mL/m2. Sex and age were not limited. Exclusion criteria were 1) congenital heart disease other than bicuspid aortic valve, 2) arrhythmia (ventricular tachycardia, supraventricular tachycardia, atrial fibrillation, and so on) at the time of echocardiographic examination, 3) post-operative state of valvular disease, and 4) severe valvular heart disease other than AS.
Geographic data were collected including sex, age, height, body weight, complications, past medical history, history of present illness, and treatment until the occasion of the echocardiographic examination. Echocardiographic data were LV internal dimension in end-diastole (LVDd), LV internal dimension in end-systole (LVDs), LV ejection fraction (LVEF), interventricular thickness (IVS), LV posterior thickness (PW), LV mass index (LVMI), SVI, and AVAi. Heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were at the occasion of echocardiographic examination.
The AT, ET, and AT/ET as well as peak transaortic Vmax were analyzed from transaortic Doppler recordings of 3C, 5C, and R approaches (Figure 1 ). Both of ET and AT were corrected according to HR by dividing by (R-R interval)1/2, and they were named as cET and cAT. AVA was obtained by continuous equation using an approach of which transaortic Vmax was the highest of all approaches.
All of measurements of time interval were average of 3 consecutive beats. Sweep speed on the screen for measurements were used as 50-100mm/sec, depending on the HR of the patients. Doppler gain was adjusted properly in each patient, and it was kept constant within the patient.
Intra-observer variability and inter-observer variability of time measurements: Intra-observer variability of AT, ET, and AT/ET were assessed by regression analysis and Bland-Altman plot.14,15 Total of 90 beats (each 9 beats from 10 cases) was measured once, then the same 90 beats were measured on the other day by the same investigator for the intra-observer variability.
Inter-observer variability of AT, ET, and AT/ET were also assessed. Total of 150 beats (51 beats of 3C, 51 beats of 5C and 48 beats of R from 38 cases) were measure by the 1st investigator, then the same beats were re-measured by the 2ndinvestigator as the blinded to the 1st measurements. Then, to compare the data of the apical and R approach, 51 beats of R data were added for analysis. Finally, 102 beats of apical approach (51 beats of 3C and 51 beats of 5C) and 99 beats of R approach were analyzed by regression analysis and Bland-Altman plot.
Statistical analysis: Continuous variables are expressed as mean+ SD. Commercially available software (StatFlex ver.6, Artech Co. Ltd.) was used for statistical analysis. Analysis of variance (ANOVA) and post-hoc test (Dunn) was used for multiple comparison. Analysis of covariance (ANCOVA) was used for comparison of regression lines (JUMP pro Windows, ver 13). Bland-Altman plot was used for intra- and inter-observer variability. P<0.05 was assumed as statistical significance.
This study was approved by an Institutional Review Board of Yamaguchi University Hospital (H30-041-[1]). The Institutional Review Board approved this retrospective analysis of clinically acquired data and waived the need for written informed consent.