tailieunhanh - Diastolic Heart Failure – part 4

Mối quan hệ giữa vận tốc cơ tim và chức năng tâm trương Rối loạn chức năng tâm trương tim gây ra bởi thất bất thường trong thư giãn, tăng độ cứng, hoặc một sự kết hợp của cả hai là một nguyên nhân quan trọng của bệnh tật ở những bệnh nhân bị bệnh tim | 7 Myocardial Velocities as Markers of Diastolic Function Jarosiaw D. Kasprzak and Karina A. Wierzbowska-Drabik Relationship Between Myocardial Velocities and Diastolic Function Cardiac diastolic dysfunction caused by ventricular abnormalities in relaxation increased stiffness or a combination of both is an important cause of morbidity in patients with heart disease. A direct evaluation of diastolic function requires invasive simultaneous high-fidelity measurements of left ventricular LV pressures and volumes. This experimental and physiologic standard is rarely feasible in a clinical setting as it requires cardiac catheterization with specialized measurements and is thus poorly suited for repetitive assessment or screening purposes. Therefore in clinical practice noninvasive methods such as echocardiography and recently magnetic resonance imaging MRI are principal tools for the assessment of global and local myocardial function. Doppler echocardiography is currently a widespread noninvasive method used for the assessment of cardiac physiology. Pulsed wave Doppler measurements of ventricular filling velocities and pulmonary vein flow are now widely available and routinely used to estimate LV diastolic function. An important limitation ofthis approach however is its dependence on loading conditions with an increase in the velocity of early mitral inflow and pseudonormalization of the filling pattern due to a compensatory increase in left atrial pressure as LV diastolic dysfunction progresses Figure . Doppler flow measurements are also limited by providing only a global insight into ventricular dysfunction. However ventricular filling is physi ologically determined by suction that is instantaneous pressure gradients created initially by relaxation of the myocardium after the closure of the aortic valve and later in the cardiac cycle by the balance between active contraction force of atria if present and late diastolic ventricular pressures determined by .