ABSTRACT
The electrophysiologic study is performed by inserting electrode-tipped catheters into the body and positioning them within the heart. In a typical diagnostic study, the baseline intracardiac intervals, RR, AH, and HV, are measured, and the responses to pacing from different sites in the atria and ventricles are analyzed. Precise measurements of AV conduction can be performed with intracardiac recording. In addition to the basic surface ECG measurements of the PR, QRS, QT, PP, and RR intervals, in an electrophysiologic study, atrioventricular conduction can be further analyzed by quantifying the AH and HV intervals. Significantly prolonged AH intervals in the lack of reversible factors may represent high vagal tone, intrinsic AV nodal disease, or conduction down the slow pathway of the atrioventricular node. Retrograde conduction, measured by the VA interval, the time between ventricular depolarization to the earliest atrial depolarization is also helpful in the study of supraventricular tachycardias.
