Intensive training is associated with hemodynamic changes that typically induce an enlargement of cardiac chamber. Despite LA dilatation in athletes has been interpreted as a benign adaptation, little evidence is available. The aim of this thesis is to demonstrate that LA size changes in response to alterations in loading conditions and to analyse atrial myocardial function in athletes through the application of novel echocardiographic techniques. We found that top-level athletes exhibit a dynamic morphological and functional LA remodelling, induced by training, with an increase in reservoir and conduit volumes, but stable active volume. Training causes an increase in biatrial volumes which is accompanied by normal filling pressures and stiffness. These changes in atrial morphology are not associated with respective electrical changes. Extending the evidence from adult athletes to children, we found that training-induced atrial remodelling can occur in the early phases of the sports career and is associated with a preserved biatrial function. Finally, in a meta-analysis study of the available evidence we demonstrated that atrial function and size are not affected by aging. In conclusions, athlete’s heart is characterized by a physiological biatrial enlargement. This adaptation occurs in close association with LV cavity enlargement, is dynamic and reversible. This increase in biatrial size is not intrinsically an expression of atrial dysfunction. Indeed, in athletes the atria are characterized by a preserved reservoir function, normal myocardial stiffness, and dynamic changes in response to different loading conditions.

The general purpose of this thesis is to establish the ability of Speckle Tracking Echocardiography (STE) in assessing left atrial (LA) response to pressure and volume overload respectively in aortic stenosis (AS) and mitral regurgitation (MR), and to evaluate its accuracy in predicting LA and right ventricular (RV) fibrosis in patients with end-stage heart failure (HF) undergoing heart transplantation (HTx). I demonstrated that assessment of left ventricular (LV) long axis systolic velocity and amplitude of excursion is more sensitive than simple determination of ejection fraction (EF) for revealing the beneficial impact of MR surgery on overall LV systolic performance. Severe symptomatic AS is associated with LA enlargement and compromised mechanical function with a high incidence of peri-operative atrial fibrillation (AF). Valve replacement reverses these abnormalities and regains normal atrial function, a behaviour which is directly related to the severity of pre-operative LV outflow tract obstruction. Early identification of LA size and function disturbances, as shown by myocardial strain measurements might contribute to better patient’s recruitment for a safe valve replacement. In late stage HF patients, the right ventricle is enlarged, with reduced systolic function due to significant myocardial fibrosis. RV free wall myocardial deformation is the most accurate function measure that correlates with the extent of RV myocardial fibrosis and functional capacity. In patients with preserved EF, severe MR masks LV and LA myocardial dysfunction and correlates with symptoms and post-operative cavity function instability. Three months after MVR, the underlying myocardial disturbances are unmasked suggesting that most pre-operative measurements are subject to loading conditions. Finally LA volume and PALS remain the main predictors of post-operative AF, thus should be used for stratifying surgical risk. STE has been shown to accurately determine the severity of impairment of LA myocardial function shown by suppressed PALS which was the strongest predictor of the presence and extent of fibrosis, over and above other structure and function parameters. These findings may assist in better stratifying patients with end stage HF and identifying particularly those requiring HTx.

The general purpose of this thesis is to establish capability and accuracy of speckle tracking echocardiography (STE) in assessing left atrial (LA), left ventricular (LV) and right ventricular (RV) function and their correlation with myocardial fibrosis, filling pressure and clinical outcomes in advanced heart failure (HF) patients before and after heart transplantation (HT). I demonstrated that HT recipients had impaired LV twist dynamics in the form of reduced rotation twist angle and untwist rate but time to peak twist was not different from the age matched controls and other cardiac surgical patients. With a longitudinal study conducted on patients with refractory HF, the best prognostic power has been shown by RV strain analysis. Among the indexes of LV function, the LV ejection fraction (LVEF) demonstrated the lowest diagnostic accuracy; instead LV global circumferential strain (GCS) showed a better sensitivity and specificity than LV global longitudinal strain (GLS). When analyzing the relationship between different severity of myocardial fibrosis and LV cavity function, the strongest function parameter that correlated with severity of myocardial fibrosis was GLS. In contrast, none of diastolic LV function or even measures of exercise capacity correlated with myocardial fibrosis. In patients with end-stage HF, global peak atrial longitudinal strain (PALS), an index of atrial reservoir function was dependent by pulmonary capillary wedge pressure (PCWP) and LV fibrosis, but not influenced by LV systolic function. Results from this study confirm previous evidence of correlation between impaired global PALS and increased PCWP.