Catheter ablation techniques for atrial fibrillation have undergone an extensive evolution, starting with linear lesions in the right, then the left atria before being superseded by ablation of triggers, mainly from the pulmonary veins. We investigate the feasibility and results of combined pulmonary vein and linear ablation utilizing a specific linear lesion connecting the lateral mitral annulus to the left inferior pulmonary vein(left isthmus). Methods: 115 patients(101 M; 54±9 years) with paroxysmal atrial fibrillation(7±5 years) resistant to 4±1.6 anti-arrhythmic drugs were studied. After electrophysiologically guided disconnection of all four pulmonary veins, the left isthmus line was performed with an irrigated tip catheter. Complete linear block was demonstrated during coronary sinus pacing by local mapping looking for widely separated double potentials and confirmed by differential pacing. Mapping and ablation from within the coronary sinus was performed if an epicardial gap was detected after unsuccessful endocardial radiofrequency delivery. Results: 100%of pulmonary veins were successfully disconnected and the left isthmus line was complete with bi-directional block in 88%after a mean of 22±12 min of endocardial radiofrequency delivery in 44 patients. In 58 patients, additional radiofrequency delivery was required from within the coronary sinus for 5±5 min. After a follow-up of 6.5±2.6 months and a mean of 1.4±0.6 procedures/patient, 79%were in stable sinus rhythm without antiarrhythmic drugs. Conclusion: the left isthmus line is feasible and safe and when performed in addition to pulmonary veins isolation can contribute to an increased success rate. Catheter ablation techniques for atrial fibrillation have undergone an extensive evolution, starting with linear lesions in the right, then the left atria before being superseded by ablation of triggers, mainly from the pulmonary veins. We investigate the feasibility and results of combined pulmonary vein and linear ablation utilizing a specific linear lesion connecting the lateral mitral annulus to the left inferior pulmonary vein (left isthmus). Methods: 115 patients (101 M; 54 ± 9 years) with paroxysmal atrial fibrillation (7 ± 5 years) resistant to 4 ± 1.6 anti-arrhythmic drugs were studied. After electrophysiologically guided disconnection of all four pulmonary veins, the left isthmus line was performed with an irrigated tip catheter. Differential pacing. Mapping and ablation from within the coronary sinus was performed if an epicardial gap was detected after unsuccessful endocardial radiofrequency delivery. Results: 100% of pulmonary veins were successfully disconnected and the left isthmus line was complete with bi-directional block in 88% after a mean of 22 ± 12 min of endocardial radiofrequency delivery in 44 patients. In 58 patients, additional radiofrequency delivery was required from within the coronary sinus for 5 ± 5 min. After a follow-up of 6.5 ± 2.6 months and a mean of 1.4 ± 0.6 procedures / patient, 79% were in stable sinus rhythm without antiarrhythmic drugs . Conclusion: the left isthmus line is feasible and safe and when done in addition to pulmonary veins isolation can contribute to an increased success rate.