Biomedical subjects

Pedro Adragão

Publications and source records attributed to Pedro Adragão.

21 records · Page 2Linked to original sources

PubMed2002

Atrial fibrillation and effective refractory period of the pulmonary vein ostia.

BACKGROUND: The pathogenesis of atrial fibrillation (AF) is not completely understood. The role of pulmonary veins (PV) in AF initiation is documented, and the recent demonstration of persistent fibrillatory activity in an isolated PV suggests that the PV play a role in the maintenance of AF. OBJECTIVE: Since AF is facilitated by multiple reentry circuits in atrial tissue with short effective refractory periods (ERP) and prolonged conduction times, we investigated whether PV have shorter ERP compared with the left atrium (LA). POPULATION AND METHODS: The study population consisted of five male patients, between 45 and 78 years of age, with normal sized LA; three had coronary artery bypass surgery (and no previous history of atrial arrhythmias) and two had paroxysmal lone AF refractory to antiarrhythmic drugs and were referred for percutaneous ablation with radiofrequency energy. In the surgical patients, epicardial bipolar pacing wires were inserted in the PV ostia and LA roof at the end of the procedure. Post-operatively, the pacing wires were used to determine atrial thresholds and ERP in the PV ostia and LA roof. In the AF patients, atrial thresholds and ERP at these locations were obtained with the mapping/ablation catheter before and after PV isolation. ERP were determined with a basic pacing cycle length of 500 ms and a single extrastimulus with an initial coupling interval of 350 ms, gradually decreased (10 ms at a time) until atrial capture failure or AF induction. RESULTS: ERP in the LA roof were longer than 210 ms. The shortest ERP was always obtained in a PV ostium, with the shortest in the left PV ostia. The ERP values of the right inferior PV most resembled those of the LA roof. In patients referred for ablation, AF was induced when PV ostia with ERP shorter than 200 ms were stimulated. CONCLUSION: In the present study, the ERP of PV ostia were shorter than LA ERP, possibly explaining not only the presence of ectopic foci in the PV ostia, but also sustained fibrillatory activity in isolated PV, despite conversion of the atria to sinus rhythm. This fact may also explain the higher success rate and the preference for PV isolation in AF ablation.

Aged↗

PubMed2002

Evaluation of bilateral pulmonary vein isolation for the treatment of atrial fibrillation: value of postoperative electrophysiological study.

OBJECTIVE: To evaluate electrophysiological changes after bilateral pulmonary vein isolation in patients undergoing mitral valve surgery and to relate the clinical outcome at 1-year follow-up with the results of the postoperative electrophysiological study. METHODS: Prospective study of patients with atrial fibrillation undergoing bilateral pulmonary vein isolation using radiofrequency energy and concomitant mitral valve surgery. Pulmonary vein isolation was performed with a heptapolar catheter. Each set of up to 7 simultaneous applications aimed at a maximal duration of one minute and a maximal preset temperature of 70 degrees C. Energy delivery (< 150 watts) was controlled by thermosensors located on each electrode. Before hospital discharge, all patients presenting sinus rhythm underwent an electrophysiological study, using epicardial pacing wires placed during surgery. Isolated areas were compared to the non-isolated left atrium with respect to electrogram amplitudes and atrial capture thresholds. At one-year follow up, cardiac rhythm was assessed in all patients and correlated with the results of the postoperative electrophysioloical study. RESULTS: The study population consisted of 20 patients with mitral valve disease (mean age 59 +/- 11 years), chronic atrial fibrillation present for 0.5 to 18 years and dilated left atria (55 +/- 11 mm assessed by M-mode echocardiography). The radiofrequency procedure added, on average, 7 minutes (3 to 17) to the duration of the mitral valve surgery. No patient died or suffered surgical complications. Eleven patients presented sinus rhythm before hospital discharge. The electrogram amplitude inside the isolated zones was less than 25% of that in nonisolated areas (0.3 +/- 0.2 mV versus 2.1 +/- 1.7 mV, p = 0.002). Atrial capture thresholds were significantly higher for the isolated areas (13.5 +/- 9.3 mA versus 8.5 +/- 4.0 mA; p < 0.05). At one-year follow-up, nine patients maintained atrial fibrillation, nine remained in sinus rhythm and two lost sinus rhythm to atrial fibrillation. In both these patients, the reduction in electrogram amplitude inside the isolated zones was similar to that of the remaining patients discharged in sinus rhythm. However, postoperative electrophysiological studies in these patients showed that atrial capture thresholds for isolated areas had not increased significantly (8 mA and 6 mA, respectively). CONCLUSION: Rhythm at discharge after bilateral pulmonary vein isolation tends to remain at one-year follow up. Radiofrequency-induced modifications in electrogram amplitudes may be less important than increases in pacing thresholds of isolated zones with respect to maintenance of sinus rhythm.

Atrial Fibrillation↗

PubMedDate not supplied

Epicardial electroanatomical mapping for intraoperative evaluation of bilateral pulmonary vein isolation.

UNLABELLED: Eight patients (pts; 2 female, 58 +/- 12 yrs) with paroxysmal atrial fibrillation (AF) (duration 39 +/- 20 months) underwent AF surgery, with concomitant myocardial revascularization in 2 pts and myomectomy in 1 (HOCM). AF was idiopathic in the remaining 5 pts. AF surgery consisted of bilateral isolation of the pulmonary veins (PV) using radiofrequency (RF) energy applied epicardially by a heptapolar catheter (Thermaline) in 5 pts and by a new system (Atricure) in 3 pts. For the former, each set of 7 simultaneous applications aimed at a maximum duration of 2 + 2 min., preset temperature 80 degrees C and output 150 watts. With the new system, bipolar applications were carried out; energy delivery was controlled by impedance monitoring and applications were ended after abrupt, sustained elevation of impedance. Epicardial bipolar voltage mapping (CARTO) was performed before and after each RF procedure. Using the navigator catheter, points were recorded at the insertion of each PV and at the non-isolated left atrial posterior wall. The amplitude of the local electrograms (LE) was measured before and after RF applications. If the LE amplitude inside the isolated zone was not 0.1 mV and not reduced by > 80%, a second application was performed. A maximum of 2 epicardial applications were carried out in each pt and if the final result was unsatisfactory, further endocardial applications were performed. RESULTS: Baseline LE amplitudes were > 1 mV in all cases. Successful isolation of right PVs was achieved in 7 pts, after one set of applications in 5 and a second set in 2. Left PV isolation required 2 sets of epicardial applications in all pts, being successful in only 2; 4 pts (one with associated myomectomy and 3 with idiopathic AF) received endocardial applications. Overall, bilateral PV isolation was achieved in 5 pts. CONCLUSIONS: CARTO bipolar voltage mapping is a fast, simple means for evaluation of epicardial PV isolation.

Atrial Fibrillation↗