The M-mode (motion mode) technique has improved the diagnostic possibilities of echocardiography due to its high temporal resolution. The use of a two-dimensional (2D) image as a basis for M-mode analysis at a defined line, independent of the transducer orientation, namely the anatomic M-mode (AMM), has been proposed from the beginning of 2D echocardiography. For several years, however, this could not be accomplished due to several reasons including the limited digital memory, the relatively rough pixels of 2D images, and the low temporal resolution of the screen. The AMM has been improved by the "fully digital" machines. These are able to provide a series of digital data (direction, position, and timing) relative to any single echo received from any point of the tissue. AMM analysis, thus, can be performed in any direction, as a "normal" monodimensional echocardiogram. With respect to traditional M-mode, AMM permits a more detailed analysis of cardiac chambers diameters obtained by linear measurements, regional wall motion of the left ventricle (both at rest and during stress), and location of accessory pathways. In particular, the assessment of left ventricular regional wall motion represents the most important goal of this new technique, which results in marked reduction or even elimination of the limitations due to the subjective character of wall motion evaluation with 2D echocardiography.
Supraventricular tachycardias (SVTs) are observed in 0,1-0,4% of the paediatric population and represent an important clinical problem with related significant health and social issues. Most tachycardias are paroxysmal, being associated with sudden onset and termination, and only a relatively small number of them is permanent, namely chronic. Paroxysmal tachycardias, in addition, can be either sustained (lasting > 30 seconds) or non-sustained whenever their duration is less. Most SVTs are due to re-entry, and only atrial tachycardia and and junctional ectopic tachycardia are caused by enhanced automaticity. Atrial tachycardia, however, can also be due, although rarely, to re-entry or to triggered activity. A prompt recognition of these arrthmias in children by pediatric cardiologist is essential for a correct clinical managemet of the patients. In this review, the epidemiologic data regarding the SVTs in pediatric age are reported along with the description of the pathophysiological mechanisms and the analysis of electrocardiographic findings to be considered for a correct clinical diagnosis and a rational therapeutic approach to these arrhythmias.
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