Statistical analyses
All data are expressed as mean ± standard deviation (SD) for continuous variables. Categorical data are expressed as absolute values and percentages. All data was tested for normality using the Kolmogorov-Smirnov statistical test. Pearson’s correlation coefficients (r) or Spearman’s coefficients (rho) were used to determine relationships between haemodynamic and echocardiographic responses. VO2 was averaged every 10 seconds and were linked with corresponding S’ values every minute. E’, LVEF, GLS and circumferential strain values were linked with corresponding S’ values at rest, 5 minutes and when the RER was over 1. Values at rest, at 5 minutes and when RER was over 1 were compared using one-way ANOVA and Tukey post-hoc analyses to determine differences between groups. A scatter plot with 95% confidence interval was plotted. The augmentation curve was investigated in more detail (LVEF, systolic and diastolic volumes, LVOT VTI and GLS) and correlated with corresponding VO2peak values. Inter- and intraobserver measurement variability was performed for 5 randomly selected participants for echocardiographic parameters and for 15 randomly selected participants for CPET parameters. Two BSE accredited operators (JVZ, SB) with extensive experience in performing CPET simultaneously with echocardiography performed the inter- and intra-observer measurements. The intraclass correlation coefficient (ICC) and 95% confidence intervals was used to quantify reproducibility. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS version 20.0; SPSS, Inc). A P-value of < 0.05 was considered statistically significant.