English to Italian Medical Medical: Cardiology Echocardiography

Taken from the description of an echocardiography procedure. It is probably just a simpler way of saying "taken during the systolic stage", but I am not sure:
"4.2 Diameter of the left ventricular outflow tract measured on three parasternal long-axis frames frozen in systole. Diameters will be measured from the trailing edge of the left septal echo to the leading edge of the anterior mitral leaflet echo. The maximum dimension will be taken. If there is reverberation artifact from calcium, the leading edge to leading edge convention will be used; if this artifact is excessive, the measurement will not be made. The best measurement (usually at the preoperative examination) will be assumed to remain constant throughout the study."