| Popis: |
Strain rate (SR) is considered as an accurate index of myocardial contractility, capable of differentiating regional myocardial contractions from hypokinetic ones. It is not dependent on adjacent myocardial motion or heart translation. Clinical studies proved this method to be useful in case of heart disease but detailed analyses, homogeneous normal reference parameters, and studies about atrial myocardium are still scanty. The aim of this study was to evaluate longitudinal SR of the left myocardial ventricle and atrium in normal subjects.Nineteen normal subjects were examined with tissue Doppler imaging; SR values were obtained off-line on images stored by internal software using the curved M-mode of the left ventricle and atrium. Mean SR values were obtained at the distal, mid, and basal left ventricular segments of the septum and lateral wall, and at the basal and distal left atrial segments of the septum and lateral wall.Ventricular SR values showed a negative systolic peak, two positive peaks at rapid filling and one at late filling. In the distal segments systolic SR values were lower and that of rapid filling were higher. Systolic events showed a progression from the base to the apex; the diastolic ones had an opposite trend. SR values of the closest atrial segments to the annulus showed the same progression as the ventricular ones; in the distal segments systolic SR was positive and diastolic SR was negative. The atrioventricular sequence of the cardiac cycle is identified.The method to obtain SR is semiautomatic and objective; image acquisition at a frame rate100/s identifies accurately the components of the SR curves. The analysis of the progression of events can allow to study ventricular and atrial synchronization of contraction, relaxation, and compliance. |
