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Paroxysmal Supraventricular Tachycardia



Paroxysmal supraventricular tachycardia, or PSVT, is usually brief  and is self-limiting, as seen in this example.   The rate here suddenly accelerates from about 90 to almost 180, then drops back down to the original rate.  Notice that during this burst there is no change in shape of the QRS complex.  This tells us that there is no change in the functioning of the specialized conduction system from the junction downward.  Something has obviously changed above the junction: there is a runaway pacemaker that has propagated this burst.  Notice how the P-wave changes at the onset of this burst (best seen in II and III).