PO-04-078 WHEN THE Q RUNS AWAY FROM P: A CASE OF EXTREME MOBITZ TYPE I

Abstract

Advanced infranodal conduction disease usually presents with Mobitz 2 pattern and normal or mildly prolonged conducted PR intervals, whereas advanced AV node disease presents with Mobitz 1 pattern and more pronounced PR prolongation of conducted beats. AV node conduction properties can vary, with some patients demonstrating markedly prolonged PR intervals. We present a case of extreme PR prolongation and highly unusual Mobitz 1 patterns. To emphasize the variable presentation of AV node disease. N/A A 60 year old man with a history of Tetralogy of Fallot had serial repair surgeries over the years, including a Blalock Tausig shunt, Tetralogy of Fallot repair with pulmonary valve replacement, tricuspid valvuloplasty with chordal re-attachment, and closure of a cleft in the septal tricuspid valve leaflet. He had a dual chamber pacemaker for second degree AV block and RBBB. Due to recurrent tricuspid valve dysfunction, his pacemaker and leads were explanted at the time of repeat tricuspid valve surgery. Post-operatively, the surgical temporary epicardial pacing wires were not initially used, and various forms of asymptomatic Mobitz type 1 AV block were seen on serial ECGs. Careful scrutiny of the ECGs showed that the PR interval ranged from 640 ms to over 1300 ms. The markedly prolonged PR intervals led to highly unusual AV relationships, including overlapping PR intervals, as well as 1:1 and 2:1 AV conduction patterns that could only be properly deciphered in the context of other ECGs. When 2:1 AV conduction was seen, temporary pacing was implemented. He subsequently underwent bi-v pacemaker implantation to achieve proper AV and VV synchrony, in the context of concurrent LV dysfunction. AV conduction patterns can become complex in the setting of AV node disease, and more dramatically so in the context of congenital heart disease and valve surgery. Associations between specific P waves and QRS complexes should be ascertained to properly appreciate AV node disease severity. In the presented case, cursory ECG assessment led the ICU clinical team to conclude that AV conduction in the post-op setting followed a simple Mobitz 1 pattern with typical PR intervals. Therefore surgical temporary pacing wires were not utilized until the patient developed 2:1 AV conduction with more marked bradycardia. With careful ECG analysis, the severity of AV node dysfunction could be properly assessed and managed.