Fig. 3
Focused principal component analysis for the association between echocardiographic parameters and cardiac biomarkers: [troponin (a) and NT-proBNP (b)] in critically ill patients with coronavirus-19 sepsis. Focused principal component analysis (FPCA) is a simple graphical display of correlation structures focusing on a particular dependent variable. The display reflects primarily the correlations between the dependent variable and all other variables (covariates), and secondarily the correlations between the covariates. The dependent variable [high-sensitive troponin T (TNT) in a and N-terminal pro b-type natriuretic peptide (BNP) in b] is at the center of the each diagram, and the distance of this point to a covariate faithfully represents their pairwise Spearman correlation coefficient (using ranked values of continuous variables). Variables positively and negatively correlated with each dependent variable (TNT and BNP) are in green and yellow, respectively. Covariates significantly correlated with the dependent variable (i.e., p value < 0.05) are inside the red circle. The diagram also shows relationships between covariates as follows: correlated covariates are close (for positive correlations, allowing identification of clusters) or diametrically opposite vis-à-vis the origin (for negative correlations), whereas independent covariates form a right angle with the origin. IVC, maximal diameter of inferior vena cava in mm; EA, ratio of early to late diastolic wave velocities at the mitral valve; Ee, ratio of early pulsed-wave Doppler to early tissue Doppler diastolic wave velocity at the lateral mitral valve annulus; EF, LV ejection fraction in %; AS, absolute values of global LV longitudinal peak systolic strain in %; sm, tissue Doppler peak systolic wave at lateral mitral annulus in cm s−1; VAC, ventricular-arterial coupling; ME, LV end-systolic maximal elastance in mmHg mL−1; AE, end-systolic arterial elastance in mmHg mL−1; SVR, systemic vascular resistance in mmHg L−1 min; DAP, diastolic arterial pressure in mmHg; PCD, pulmonary circulatory dysfunction; TAPSE, tricuspid annulus plane systolic excursion in mm; st, tissue Doppler peak systolic wave at tricuspid lateral annulus in cm s−1