At Children's Healthcare of Atlanta, children who have irregular heart rhythms are often referred for evaluation. Sometimes they also need a procedure to correct their irregular heart rhythm. An echocardiogram is routinely used as part of their evaluation and follow-up. The echocardiogram including Tissue Doppler Imaging (TDI) works by bouncing sound waves off the heart similar to radar. A new echocardiogram technology, Tissue Synchronization Imaging (TSI), should help doctors look at heart function compared to heart rhythm. All three of these are noninvasive, which means they work from a probe outside the body and are not painful.