Page 54 - Advanced echocardiography in characterization and management of patients with secondary mitral regurgitation

Chapter three. Prognostic Value of Left Ventricular Global Longitudinal Strain
groups, chi-square tests were used for categorical data and the unpaired Student’s t-test or Mann-Whitney U test, as appropriate, for continuous data. Changes in hazard ratio (HR) for all-cause mortality across the LV GLS values (as a continuous variable) were investigated by fitting a spline curve (Figure 2). A threshold of LV GLS to dichotomize the population was derived from the spline curve (i.e., in which the predicted HR is ≥1). Cumulative survival rates were estimated by the Kaplan-Meier method for all-cause mortality, and a log-rank test was used to compare groups. Cox proportional hazards regression analysis was performed to investigate the association between clinical and echocardiographic parameters with all-cause mortality. The HR and 95% CI were calculated and reported. In the univariable analysis, p values <0.05 were considered statistically significant and were included in the multivariable model. To investigate the incremental value of LV GLS over clinical and conventional echocardiographic parameters to predict outcome, the likelihood ratio test was performed. The change in global chi-square values was calculated and reported. A 2-tailed p value <0.05 was considered statistically significant. Statistical analysis was performed using SPSS for Windows, version 23.0 (IBM Corporation, Armonk, New York) and R version 3.4.4 (R Foundation for Statistical Computing, Vienna, Austria).
Figure 2. Spline Curve for All-Cause Mortality According to LV GLS Prediction of all-cause mortality across a range of LV GLS, plotted as a fitted spline model on a log-hazard scale with overlaid confidence intervals. Red dashed lines represent 95% confidence intervals. Abbreviations as in Figure 1.
Results
Patient population
A total of 650 patients (mean 66 ± 11 years of age, 68% men) were included. The majority of patients were in NYHA functional class II and III, and 52% of patients had ischemic heart failure (Table 1). Table 2 summarizes the echocardiographic data for the overall population. The median LV GLS was 7.2% (interquartile range: 5.2% to 9.9%) in
52