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Atrial fibrillation (AF) is considered one of the most common of cardiac arrhythmias. Triggers from the pulmonary veins play a crucial role in its onset, yet structural and electrical changes in the atrial myocardium additionally contribute to the perpetuation of the arrhythmia. The left atrial remodeling can be assigned a key role, increasing left atrial stiffness. Experimental studies indicate that structural changes are accompanied by modifications of the electrical conduction properties of the atrial myocardium. Until now it is not clear to what degree paroxysmal atrial fibrillation (PAF) leads to changes in the atrial stiffness and the atrial conduction times. Patients with PAF who underwent pulmonary vein isolation (cryo- or radiofrequency ablation) were included. The control group consisted of patients who received an ablation because of supraventricular tachycardia (SVT), without history of AF. In both groups, we measured the conduction time along the coronary sinus catheter from proximal (CSP) to distal (CSD) in sinus rhythm (SR) as well as the duration of the P-wave at the surface ECG. Also an invasive measurement was performed of the LA-pressure in SR in both the AF-group and in the control group, of patients with a left side accessory pathway. The atrial size was measured by echocardiography along the parasternal long axis.

There were a total of 49 patients with PAF and 52 patients with SVT, of which 17 had a left-sided accessory pathway. Both groups were of similar average age (61±8 vs. 58±11 years, p=ns). Echocardiographically, a larger LA diameter was detected in PAF (42.2±4.8 vs. 34.0±5.2 mm, p<0.01). The P wave duration was significantly prolonged under PAF (106.7±20.0 vs. 97.4±18.9 ms, p=0.03). The conduction time of CSP to CSD in the PAF group was also significantly increased (73.66±13.5 vs. 56.5±11.5 ms, p<0.01), while the LA-propagation velocity was significantly slower (0.55±0.10 vs. 0.75±0.17 m/s, p<0.01). Furthermore, patients with PAF showed an increased difference between LA peak v-wave pressure and x-wave pressure nadir (8.1±2.1 vs. 6.3±2.7 mmHg, p=0.04), an indicator of increased LA stiffness. Among all patients, there was a positive correlation between LA-propagation time and LA-size (R=0.6) and between LA-propagation time and LA-stiffness (R=0.3).

Collectively, these findings demonstrate that even PAF increases LA stiffness and extends LA conduction times with a consecutive reduced LA-propagation velocity. The LA conduction times correlate with the LA stiffness and echocardiographic LA diameter and can therefore be a potential sign of atrial remodeling.

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The European Society of Cardiology
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