How should tissue Doppler tracings be measured?

Tissue Doppler, an echocardiographic modality measuring velocities of solid cardiac structures by pulsed-wave or colour Doppler, after very early experiments was introduced clinically in the early 1990s and is one of the very few recent technical innovations in echocardiography to gain quick and near-ubiquitous clinical implementation. The most widely adopted application is the registration of the mitral annular baso-apical velocity profile, at the basal septal or basal lateral left ventricular wall, which gives quantitative information on both diastolic and systolic global left ventricular function and is nowpart of the standard echoexamination. These tissue velocities have also been shown to be useful to identify subclinical cardiomyopathies, such as hypertrophic cardiomyopathy, amyloidosis, or drug cardiotoxicity. Recent data show a strong prognostic value after myocardial infarction. Another established application is right ventricular free wall velocity as a parameter of right ventricular function. Technically, tissue Doppler differs from standard pulsed-wave Doppler by using a low-pass frequency filter to keep low-velocity signals from tissue and to reject the high-velocity signals from blood. The detected velocities are low–even for right ventricular basal velocities, which are the highest tissue velocities routinely recorded, they are under 20 cm/s, and in diseased left ventricles the peaks of the S′ or e′ wave often are only a few cm/s in magnitude. In such signals, even small differences in how velocities are actually measured matter, because they lead to relatively high variations as apercentageof theabsolute value.TissueDoppler velocity–timedisplays, even though measuring reflectors in tissue, which compared with blood move with a relatively uniform velocity, produce a broad trace—they are rarely razor-thin. This so-called spectral broadening has several reasons: