title: Conventional and biventricular pacing in patients with first-degree atrioventricular block.
abstract: Recent reports suggest that first-degree atrioventricular block is not benign. However, there is no evidence that shortening of the PR interval can improve outcome except for symptomatic patients with a very long PR interval ≥0.3 s. Because these patients require continual forced pacing, biventricular pacing should be used according to accepted guidelines for third-degree AV block. Functional atrial undersensing may occur in patients with conventional dual-chamber pacing and first-degree AV block because the sinus P-wave tends to be displaced into the post-ventricular atrial refractory period (PVARP) an arrangement that may cause a pacemaker syndrome. Prevention requires programming a shorter AV and PVARP that is feasible because retrograde conduction is rare in first-degree AV block patients. A relatively new pacing mode to minimize right ventricular stimulation has been designed by eliminating the traditional AV interval but with dual-chamber backup. This pacing mode permits the establishment of very long AV intervals that may cause pacemaker syndrome. About 50% of patients undergoing cardiac resynchronization therapy (CRT) have a PR interval ≥200 ms. The CRT patients with first-degree AV block are prone to develop electrical desynchronization more easily than those with a normal PR interval. The duration of desynchronization after exceeding the upper rate on exercise is also more pronounced. AV junctional ablation is rarely necessary in patients with first-degree AV block but should be considered for symptomatic functional atrial undersensing or when the disturbances caused by first-degree AV block during CRT cannot be managed by programming.
authors.affiliation: Florida Heart Rhythm Institute, Tampa, FL, USA. ssbarold@aol.com
authors.forename: S Serge
authors.initials: SS
authors.lastname: Barold
authors.forename: Bengt
authors.initials: B
authors.lastname: Herweg
mesh_terms: D054537:Atrioventricular Block / Q000503:physiopathology / Q000601:surgery / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D058409:Cardiac Resynchronization Therapy Devices / Q000009:adverse effects; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D017410:Practice Guidelines as Topic; D012720:Severity of Illness Index; D016896:Treatment Outcome