الفهرس 
Ch 2: Speckle tracking EchocardiographyOnly 14 pages are availabe for public view
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Abstract
Rheumatic heart disease (RHD) is the second most common cause of cardiovascular morbidity and mortality in developing countries next only to atherosclerotic vascular disease Mitral stenosis (MS) is one of the key valvular pathologies seen in RHD. (76)
Mitral stenosis (MS) still leads to significant morbidity and mortality worldwide(76). Surgical options, either open or percutaneous, are the treatment of choice in severe symptomatic MS. Mitral valve replacement is now the preferred treatment due to improved valve and clinical outcomes (9) inpatients that are not fit for percutaneous mitral commissurotomy(77)
The presence of impaired left ventricular (LV) systolic function, determined by M-mode and/or two-dimensional (2D) echocardiography, is noted in 25–30% of the patients with MS (2–6).
Recent evidence from deformation imaging echocardiography (102) demonstrated the presence of subclinical LV systolic dysfunction, which was not detected with the conventional echocardiography in pure MS patients with preserved EF.(81,82)
However LVEF has several limitations. It provides an indirect measure of the LV contractile function and does not measure it directly. It is readily influenced by a number of factors including loading conditions, heart rate, etc. Most importantly, it is not sensitive enough to detect subtle changes in the contractile function and therefore not suitable for detecting subclinical myocardial damage which may have major therapeutic and prognostic implications in a variety of clinical conditions. (103)
Speckle tracking echocardiography (STE) is the most widely used technique to assess strain in a variety of clinical and research settings. By tracking myocardial speckles displacement, frame-by-frame, in an angle-independent way. (99)
A complex deformation occurs in the LV myocardium during the cardiac cycle. The deformation is described in terms of three principle strains - longitudinal, radial and circumferential. Shortening of the LV along its long-axis is denoted by longitudinal strain. The circumferential strain denotes the decrease in the circumference of the LV cavity during the cardiac cycle whereas radial strain depicts the thickening of the LV wall along its radius. During each heart beat, the apex rotates in anticlockwise direction during systole whereas the base rotates in the clockwise direction. This twisting motion of LV during systole with the opposite rotation of the LV apex and base is important to the normal systolic functioning of the LV. The subsequent untwist generates a suction force during diastole that appears to be the key mechanism driving the early diastolic filling of the LV (39)
STE based studies have confirmed that MS is characterized by a significant reduction in LV function, as demonstrated by the lower value of GLS and global circumferential strain observed in MS patients compared with normal subjects (100).