As a medical professional with expertise in cardiology, I can provide you with an accurate answer to your question regarding SVT, which stands for Supraventricular Tachycardia.

SVT is a type of tachycardia, which is a rapid heart rate. It originates above the ventricles, typically in the atria or the atrioventricular (AV) node. The complex in ECG terminology refers to the pattern seen in the QRS complex, which represents the electrical activity of the ventricles during depolarization.

In the context of an ECG, the term wide complex is used to describe a QRS duration of greater than 0.12 seconds, which suggests a slower than normal ventricular activation. This is often associated with conditions that affect the ventricular conduction system, such as bundle branch block or ventricular rhythms.

On the other hand, a narrow complex QRS duration is less than 0.12 seconds, indicating a normal or faster than normal ventricular activation.

SVT is generally associated with a narrow complex on the ECG because the abnormal rhythm originates above the ventricles and the ventricular activation is typically normal or faster. However, there are exceptions, such as in the case of SVT with aberrancy, where the QRS complex can appear wide due to an abnormal conduction through the ventricles.

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Most have a narrow QRS complex, although, occasionally, electrical conduction abnormalities may produce a wide QRS complex that may mimic ventricular tachycardia (VT). ... Sinus tachycardia is considered by most sources to be an SVT.read more >>