| Summary: | The aim of this study was to characterise the echocardiographic findings in healthy geriatric cats and to compare these to the changes in geriatric cats with various forms of primary and specific cardiomyopathy. It was predicted that from this it might be possible to derive disease specific cardiac changes. In addition, it may be possible to elucidate the affect of medication and progression of disease. A total of 134 cats, aged eight years or above, were studied. Each cat underwent a conventional echocardiographic examination (two-dimensional, spectral Doppler, and M-mode) and contemporary assessment of diastolic function (pulsed-wave Doppler tissue imaging [pw-DTI], colour M-mode propagation velocity and isovolumetric relaxation time). The cats were grouped according to either the disease process, or the diastolic filling pattern, and groups were compared. I was successfully able to record pw-DTI traces (of both radial and longitudinal velocity) from the feline myocardium. The repeatability of these measurements was assessed, and generally found to be comparable to the variability reported in humans. I found no evidence that pw-DTI velocities are affected by age in a normal geriatric cat population. Furthermore, I demonstrated no significant differences in the relationship between pw-DTI velocities and age in cats within any of the disease groups studied, although there was some variation with heart rate (as assessed by the R-R interval). In addition, I demonstrated that when grouped according to the transmitral diastolic flow pattern and the ratio of transmitral A-wave duration to pulmonary venous atrial reversal duration, the pw-DTI flow pattern recorded from the apical four chamber view (at either the lateral aspect of the mitral annulus, or mid-posterior wall) was able to differentiate normal from impaired relaxation and pseudonormal flow patterns. Analysis of echocardiographic data demonstrated that there was an increase in the thickness of the basilar interventricular septum in the majority of cats studied. Compared to unaffected cats, cats with HCM had a decrease in the E’ velocity (recorded by pw-DTI at the interventricular septum) and a tendency towards a decrease at the lateral aspect of the mitral annulus (recorded from the left apical four-chamber view). This work, for the first time, uses novel ultrasound techniques to investigate the myocardial dynamics in normal geriatric cats, cats with primary hypertrophy and cats with a range of specific cardiomyopathies. The use of these techniques has provided us with a new insight into these disease processes and has evaluated the use of this clinically applicable tool for the evaluation of feline myocardial dynamics.
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