Pasoxysmal supraventricular tachycardia (PSVT or SVT) is an episodic rapid rhythm that may or may not lead to clinical symptoms. SVT is most commonly the result of a re-entry pathway involving the AV node and can be micro- or macroscopic in structure. On the EKG, SVT is a regular, narrow complex tachycardia unless the impulses are conducted abarently due to myocardial ischemia or if a bundle branch block existed before the SVT initiated. There should not be P waves if the patient it truly in SVT. At high conduction rates, it is sometimes difficult to tell the difference between SVT and A-Fib because the complexes are generated so close together, the small variation in RR interval of rapid A-fib can not easily be detected by the human eye. If there is uncertainty of which rhythm is present, a caliper or other measuring device should prove helpful in differentiating a static RR interval associated with SVT from irregular RR intervals of A-Fib.
See examples of SVT