Figure 2. Transthoracic parasternal short axis view obtained in the prone position by the TEE probe at angle 77°
A: At the level of mitral valve leafletsB: At the level of papillary muscles obtained by clockwise rotationC: At the level of great vessels obtained by counterclockwise rotation

Statistical analysis

Continuous variables were presented as means ± standard deviation (SD) or medians with interquartile range (IQR) and compared with Student’s t-tests or the Mann-Whitney U test. Categorical variables were reported as numbers and percentages and compared with the Chi- square or Fisher exact test (for cells < 5).
A Pearson correlation coefficient was computed to assess the relationship between each of the LV dimensions, EF, aortic root and LA dimensions indexed to body surface area in both the prone and the supine positions. An independent-samples t-test was conducted to compare differences in the mean diameter for each parameter between both positions. Bland-Altman plots were performed to show accuracy and agreement between each of LV- end diastolic diameter (LVEDD), LV- end systolic diameter (LVESD), septal wall thickness (SWT), posterior wall thickness (PWT), and aortic root dimensions (AoR) in the prone position vs the standard supine position.
Two-tailed p values < 0.05 were considered significant. Statistical analyses were performed by using the IBM Statistical Package for Social Sciences (SPSS) for Windows version 25.0 (IBM SPSS Inc. USA).

Results

Overall, 30 non-COVID-19 patients were enrolled in our study. Mean (SD) age of patients was 35 (10.9) years and 11 patients (36.7%) were females. One patient had hypertension, 1 patient had non-insulin dependent diabetes mellitus (DM) and 8 patients were smokers. Mean (SD) BMI was 26.4 (5.9) kg/m2 and mean (SD) BSA was 1.8 (0.2) m2.
There were no significant differences between LVEDD, LVESD, SWT, PWT and AoR dimensions in the prone vs the supine positions. While there was a significant difference between the mean ejection fraction (60.3% vs 63.1%, P = 0.014) and mean LA dimensions (1.8 [0.2] vs 1.9 (0.2) cm/m2, P < 0.001) in the prone position as compared to the supine position (table 1).

Table 1. Comparing differences between each of the LV dimensions, ejection fraction, aortic root and LA dimensions in the prone vs supine positions.