Mechanism of atrial fibrillation: Decremental conduction, fragmentation, and ectopic activity in patients with drup resistant paroxysmal atrial fibrillation and structurally normal heart

Mechanism of Atrial Fibrillation: Decremental Conduction, Fragmentation, and Ectopic Activity in Patients with Drug Resistant Paroxysmal Atrial Fibrillation and Structurally Normal Heart. Atrial fibrillation (AF) has been associated with premature beats and decreased atrial conduction velocity. This study examined a new index of dynamic inter-atria] conduction time (iaCT) in patients with paroxysmal AF (PAF). We compared 42 consecutive patients with paroxysmal AF (mean age = 52 16 years) without structural heart disease with 39 age-matched patients (mean age = 49 15 years) who underwent oblation of junctional tachycordios. Prior to investigation, all antiarrhythmic drugs were discontinued for an appropriate period of time. The following measurements were made: baseline iaCT (iaCTb) between high right atrium (HRA) and distal coronary sinus, iaCT during HRA pacing S1S1 600 ms (iaCTS1), maximum prolongation of iaCT during S2 and S3 delivery (iaCTS2, iaCTS3). We then derived the decremental index (DI), the maximum percent prolongation of iaCT = iaCT S3-iaCTS1/iaCTS1%. In patients with PAF, iaCTb was 81.3 +/- 24 ms versus 59.5 +/- 14 ms in controls (P = 0.0001). Atrial fibrillation was reproducibly and easily induced with a prominent increase in iaCT in 11 patients with AF In this subgroup DI was 92 +/- 17%, compared to 45 +/- 21 % in the other patients with AF (P = 0.0001) and 21 +/- 15% in the control group (P = 0.0001). Spontaneous isolated or repetitive ectopic activity was observed in 11 patients with AF (26%), and decremental atrial conduction was observed in 76% of patients with AF This study supports the role of dynamic inter-atrial conduction disturbances in patients with lone PAE The DI may be a new index of vulnerability to paroxysmal AF.