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Atrioventricular conduction abnormalities and atrioventricular blocks: role of electrophysiology testing

In sinus bradycardia, the role of electrophysiology studies is not established. A marked prolongation of the corrected sinus node recovery time (>800 ms) is a highly predictive but insensitive sign for sick sinus syndrome. In atrioventricular conduction disturbances, an electrophysiology study may be necessary both for the establishment of atrioventricular block as the main cause of symptoms, and for identification of the anatomical site of block that may dictate the potential need of permanent pacing. Prediction of development of complete heart block may not be possible. An HV interval greater than 70 ms is a non-specific predictor of development of high-grade atrioventricular block, whereas an HV interval greater than 100 ms is highly predictive but insensitive. Drug testing with adenosine triphosphate/adenosine, and procainamide has a rather limited diagnostic yield in patients with atrioventricular conduction disturbances.