DEVELOPMENTS IN CARDIOVASCULAR ULTRASOUND - PART 3 - CARDIAC APPLICATIONS

Echocardiography is still the principal, non-invasive method of invest igation for the evaluation of cardiac disorders. Using Doppler ultraso und, indices such as coronary flow reserve and cardiac output can be d etermined. The severity of valvular stenosis can be determined by the area of the valve, either directly from 2D echo, from pressure halftim e calculations, from continuity equations or from the proximal isovelo city surface area method. Alternatively, the severity of regurgitation can be estimated by colour or pulsed ultrasound detection of the back -projection of the high-velocity jet into the chamber. Myocardial wall abnormalites can be assessed using 2D ultrasound, M-mode or analysis from the radio-frequency ultrasound signal. Doppler tissue imaging can be used to quantify intra-myocardial wall velocities, and 3D reconstr uction of cardiac images can provide visualisation of the complete car diac anatomy from any orientation. The development of myocardial contr ast agents and associated imaging techniques to enhance visualisation of these agents within the myocardium has aided qualitative assessment of myocardial perfusion abnormalites. However, quantitative myocardia l perfusion has still to be realised.