The role of bachmann’s bundle during chronic atrial fibrillation in patients with mitral valve disease

Poster 5 new technique in relation to the known predictors for prediction of recurrent AF after successful ECV. Methods: In total 43 patients underwent a trans-thoracic echocardiographic examination 3 days after successful ECV for measurement of the right and left atrial area and the LV ejection fraction . In addition we measured the PA-tdi-interval, defined as the time from the onset of the P-wave in the electrocardiogram (lead II) till the peak of the atrial tissue Doppler velocity curve from the lateral wall of the left atrium in the apical four chamber view. Patients with antiarrhythmic drugs (except low dose sotalol 40 mg bid) were excluded from the study. Endpoint was recurrence of AF one month after ECV. Results: During 1 month follow-up, AF recurred in 16 patients (37%). Patients with a recurrence of AF had a larger LA size compared to patients who remained in SR (47⫾ 4 versus 44 ⫾ 7ms, respectively, p⬍0.01). They also had a significantly longer PA-tdi interval compared to patients who remained in SR (174.80⫾ 52.76 versus 151.98 ⫾ 23.90 ms, respectively, p⬍0.01). Multivariate analysis demonstrated that the PA-tdi interval was the only independent predictor for recurrences of AF. Conclusion: The total atrial activation time as measured by atrial tissue Doppler imaging is able to identify an atrial substrate which is vulnerable for recurrent AF. This new parameter could become an easy to use tool for risk stratification in AF. P5-47 THE ROLE OF BACHMANN’S BUNDLE DURING CHRONIC ATRIAL FIBRILLATION IN PATIENTS WITH MITRAL VALVE DISEASE Natasja M. De Groot, MD, Pieter Voigt, MD, Jerry Braun, Martin J. Schalij, MD, PhD and Maurits Allessie. Leiden University Medical Center, Leiden, Netherlands and CardioVascular Research Institute Maastricht, Maastricht, Netherlands. Introduction: Animal studies have shown that bachmann’s bundle (BB) is essential for development of multiple reentrant circuits perpetuating atrial fibrillation (AF). Mapping of BB in humans has sofar not been performed. In this study, high density epicardial mapping of BB was performed to study conduction characteristics of fibrillation waves across BB during chronic AF in humans. Methods: Epicardial mapping studies of BB were performed in pts (n⫽10, age 58⫾3 yrs) with chronic AF during cardiac surgery for mitral valve disease with a template containing 60 unipolar electrodes (inter-electrode distance 1.5 mm). Ten seconds of AF were recorded from the middle (MBB), right (RBB) and left site of BB (LBB). Isochronal maps were off-line constructed. For each mapping site, AF cycle length (ACFL), conduction velocity (CV) and the incidence of conduction block (CV⬍ 7.5 cm/s) was determined. Fibrillation potentials were classified according to the degree of fractionation. Results: 3988⫾2039 fibrillation potentials and 197⫾56 fibrillation maps/pt were analysed. In most pts, multiple waves separated by arcs of conduction block were observed. In 3 pts, only single waves propagating at high CV were present. There were no preferential conduction directions. Electrophysiological variables are summarized in table 1. CV was slower and conduction block occurred more frequently at MBB compared to RBB and LBB (CV: MBB: 29⫾18cm/s* vs RBB:46⫾30cm/s, LLB: 52⫾20cm/s, p⬍0.02, conduction block: MBB:20⫾10%* vs RBB:5⫾3%, LLB:7⫾2%, p⬍0.01). Conclusion: There is a large inter-individual variation in activation patterns across BB during chronic AF in MVD patients. The results of this study suggest that BB is 1) a crucial pathway of conduction for fibrillation waves propagating from the right to the left atria or vice versa, or 2) a perpetuator of chronic AF.

S269 P5-48 PHARMACOLOGIC CARDIOVERSION OF ATRIAL FIBRILLATION WITH A EXTRA CLASS IC DOSING IN PATIENTS ALREADY ON DAILY MAINTENANCE CLASS IC THERAPY *James A. Reiffel, MD. Columbia University, New York, NY. The Class IC antiarrhythmic drugs (AAD) propafenone, in the immediate release form tid (P-IR) and sustained release form bid (P-SR), and flecainide (F) bid are often used to reduce or prevent episodes of atrial fibrillation (AF) in patients (pt) without structural heart disease or with uncomplicated hypertension, and may be initiated in the out-pt setting. The usual maximal daily dose (MDD) is 900 mg/d for P-IR, 850 mg/d forP-SR is 850 mg/d, and 400 mg/d for F. P-SR 650 mg/d and 850 mg/d respectively approximate the PK curves of P-IR at 450 mg/d and 675 mg/d. Single doses of P-IR (usually 600 mg) and F (usually 300 mg) have been used to terminate recent-onset AF in pt not taking an AAD with efficacy rates of 70-80% by 8 hrs. To determine whether extra doses of P-IR or F could be used to convert recurrent AF episodes in pt already taking daily P-IR, P-SR, or F, but at doses less than the MDD, 23 pt with 41 episodes were given single extra out-pt doses of P-IR or F at least 3 hours after their prior drug dose to raise their total dose of P or F for that day up to the MDD. For example, for P-IR 600 mg/d, a 300 mg “bolus” dose was used; for P-IR 450 mg/d, a dose of 300 mg was used, followed in 4 hrs by another 150 mg if needed. For P-SR of 325 mg bid, 300 mg of P-IR was used, but for 425 mg of P-SR bid, no more than 150 mg P-IR was used. 70% were men, average age 55; all new AF episodes were ⬍24 hrs long before the extra dosing. Results: For daily maintenance/acute dosing 3 pt used F/F, 5 pt used P-SR/P-IR, and 15 pt used P-IR/P-IR. Conversion rates were 64%, 71%, and 68%(p⫽ns). Adverse effects were mild (e.g., nausea, vague dizziness); there was no syncope, undue bradycardia, ventricular tachyarrhythmia. Conclusions: P-IR “bolus” dosing can be used to terminate recurrent AF in pt taking daily P-IR or P-SR, as can F in pts taking F, using the usual MDD as a guide to maximal additional dosing to be considered. Such additional doses appear to be as well tolerated as they are in pt not taking daily AAD. Efficacy rates may be slightly lower in pts taking daily doses of the same agents than in pts not yet on daily maintenance therapy. Confirmatory data in a still larger set of pt would be beneficial to clinical therapy. P5-49 USE OF NIFEKALANT IN CARDIOVERSION OF PATIENTS WITH ATRIAL FLUTTER TREATED WITH OR WITHOUT CLASS I ANTIARRHYTHMIC AGENTS Norishige Morita, MD, Yoshinori Kobayashi, MD, Kenji Yodogawa, MD, Yu-Ki Iwasaki, MD, Meiso Hayashi, MD, Mitsunori Maruyama, MD, Takuya Ono, MD, Yasushi Miyauchi, MD, Toshihiko Ohara, MD, Naoki Satoh, MD, Yoshiyuki Hirayama, MD, Hirotsugu Atarashi, MD, Keiji Tanaka, MD, Takao Katoh, MD and Teruo Takano, MD. Nippon Medical School, Tokyo, Japan. Background: Nifekalant(NIF) is pure class III antiarrhythmic agent (Ikr blocker) and proved to be effective in the treatment of ventricular arrhythmias. However whether or not it has effectiveness on atrial flutter(AFL) or class I antiarrhythmic agents induced AFL(I-AFL) converted from atrial fibrillation(AF) has not been understood well. Methods: This study consisted of 32 patients with total 38 episodes of AFL who had structural heart disease with LVEF of 44⫾16 %(26males, mean age: 68⫾11y/o) . NIF(0.3mg/kg) was administered for AFL, I-AFL, and AF. In 9 episodes the maintenance dose (0.2mg/kg/hr) was needed for the termination. Seventeen episodes(34%) out of all AFL were I-AFL. Results: NIF offered an overall AFL conversion efficacy of 89.4% (34 of 38 episodes). Termination rates of AFL and I-AFL by NIF were 85.7 and 94.1% respectively (n.s.). Four episodes of AF under prior treatment with NIF were converted to AFL with use of class I drugs by which all the AFLs were predisposed to the termination(100%). Termination rate of AFL lasting more than 72 hours tended to be lower than those lasting less than 72 hours(60.0% vs 93.9%, p⬍0.1). AFL cycle length(CL), QTc, and blood