Results
Nineteen observers completed all reading sessions. Figure 2shows a summary of the accuracy (in %) of each center compared with the gold standard core lab for all parameters at rest and at peak of exercise. The average accuracy of 19 readers for all parameters was excellent in about 99.8% (range from 99.7% to 100%) (Table 3) . ICC was > 0.8 for all observers. The average agreement of the 19 readers for all parameters was excellent (ICC = 0.98). Moreover the average agreement among readers remained excellent at rest and at peak exercise for all measurements (ICC = 0.98 and 0.99, respectively) (Table 4) . Inter-observer variabilities for main exercise TTE measurements are reported in table 5 . Close inter-observer variabilities were found for both resting and peak exercise TRV (3.8 and 2.4%), RV S’ (2.9 and 2.9%), E (5.7 and 8.3%) and e’ (6 and 6.5%). Inter-observer variabilities of the RVOT Act and LVOT VTI were of 9.7 and 7.4% at rest, 12 and 9.6% at peak exercise, respectively. TAPSE showed less resting (5.3%) than peak exercise variability (8%). Moderate inter-observer variability was found for resting and peak exercise RV FAC (15 and 16%, respectively). On the other hand LVEF revealed lower resting and peak exercise mean relative differences of 7.6 and 9%, respectively.
The intra-observer quality control analysis revealed an excellent ICC of 0.97 (95% Confidence Interval: 0.96 to 0.99).