Exercise induced cardiac fatigue : insights from novel echocardiographic techniques

- The impact of prolonged strenuous exercise on cardiac function has been relatively well documented specifically related to a reduction in left ventricular (LV) filling and contractility as part of a phenomenon termed "exercise induced cardiac fatigue" (EICF). The assessment of left atrial (LA) and right ventricular (RV) function has received less attention and the mechanisms underpinning any changes are unclear. Myocardial speckle tracking (MST) IS an ultrasound technique that provides a quantification of LV, RV and LA function, allowing the assessment of myocardial strain (c) and therefore provides a unique opportunity to study the impact of prolonged exercise in a more comprehensive manner. Furthermore the absolute intra-observer reliability and the impact of chamber size with body size and functional MST ... - .... parameters are largely unknown. The aims of this thesis were to establish 1) the intra-observer reliability of peak and 'time to peak' MST parameters from the LA, LV and RV, 2) to determine the relationship between cardiac size and body size in the endurance athlete as well as determining whether MST derived parameters are associated with chamber size, 3) to assess the impact of completing a marathon (42 km) on left sided cardiac structure and function, uniquely to highlight the effects on LA function and how these contribute to LV filling and 4) to assess the impact of completing an ultra-marathon (161 km)on indices of RV structure and function and how these may influence any changes in left sided function. -)! VI Abstract A comprehensive assessment of cardiac structure and function was established throughout the thesis with the primary findings from the field based .. studies demonstrating a reduction in RV, LV and LA function in recovery from prolonged exercise. These changes were more pronounced following the ultra-marathon than from the marathon. Further analysis also demonstrates evidence of RV pressure/volume overload that appears to have a serial and parallel impact on LA and LV function which is likely to contribute to the EICF phenomenon. The field-base studies within this thesis provide some evidence to allow the proposal of the 'elevated pulmonary afterload theory' as a potential cause for EICF. Furthermore the intra-observer reliability of MST parameters, in general, is acceptable, however radial £ and strain rate (SR) are less reliable and should be interpreted with caution. MST parameters of £ and SR are generally independent of cardiac morphology and therefore absolute valuescan be used with confidence. Allometric scaling of RV and LA chamber size with body size is also recommended to provide accurate participant comparisons.EThOS - Electronic Theses Online ServiceGBUnited Kingdo