Pharmacological treatment for atrial fibrillation has a variety of purposes, such as pharmacological defibrillation, maintenance of sinus rhythm, heart rate control to prevent congestive heart failure and prevention of both cerebral infarction and atrial remodeling. Sodium channel blockers are superior to potassium channel blockers for atrial defibrillation, while both sodium and potassium channel blockers are effective in the maintenance of sinus rhythm. In general, digitalis or Ca antagonists are used to control heart rate during atrial fibrillation to prevent congestive heart failure, while amiodarone or bepridil also reduce heart rates during atrial fibrillation. Anticoagulant therapy with warfarin is recommended to prevent cerebral infarction and angiotensin converting enzyme antagonists or angiotensin II receptor blockers are also used to prevent atrial remodeling. One should select appropriate drugs for treatment of atrial fibrillation according to the patient’s condition.

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The goal of this study was to measure the effective refractory period (ERP), the conduction velocity (CV) and the wavelength (WL) after cardioversion in patients with persistent atrial fibrillation (AF) and to determine the effects of the adenosine triphosphate sensitive potassium channel (K_ATP) opening agent, nicorandil, on those parameters in patients with persistent AF.
METHODS: Patients with AF underwent elective cardioversion followed by measurement of ERP and CV before and after administration of nicorandil. Parameters were measured again one week later, and the ERP and the CV was used to calculate WL.
RESULTS: ERP was significantly shorter immediately after termination of AF than at the 1-week time point (193.4 vs. 228.7 msec p<0.01). While there was no significant difference in ERP immediately after termination of AF when comparing measurements taken before and after the administration of nicorandil, ERP at the 1-week time point was shorter after nicorandil administration than before nicorandil administration (193.4 vs. 191.4 msec, n.s.; 228.7 vs. 217.2 msec, p<0.01). Further, WL was higher at the 1-week time point after nicorandil administration than before nicorandil administration.
CONCLUSIONS: These data indicate that the electrical remodeling that occurs after cardioversion is at least partially mediated by changes in K_ATP channel behavior. Further, the electrophysiologic properties, that is, nicorandil prolonging the WL, may be of benefit in reducing the recurrence rate of AF.

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Background: Although the efficacy of pulmonary vein (PV) isolation for paroxysmal atrial fibrillation (AF) has been well-established, its effect on persistent AF has not been sufficiently established to date.
Methods and Results: In 68 consecutive patients (mean age, 52±10 years) with paroxysmal (45) and persistent (23) AF, isolation of all four PVs was performed and the subsequent clinical outcome was evaluated. In total, 268/272 PVs (99%) were completely isolated from the left atrium by radiofrequency applications. During a mean follow-up period of 11 months, 84% of patients with paroxysmal AF and 57% of patients with persistent AF were free from symptomatic AF without any antiarrhythmic drug (AAD) therapy (p=0.04). In the remaining recurrent AF patients, no significant difference between the paroxysmal and persistent AF was observed as long as they took AADs which had been ineffective at baseline (freedom from AF; 98% and 96%, respectively, p=NS). Repeat procedure performed in the 12 recurrent patients (paroxysmal AF 6, persistent AF 6) allowed 11 (92%) of them to become free from AF recurrence without AADs.
Conclusion: Electrical isolation of PV by standard catheter technique is equally and highly effective for both paroxysmal and persistent AF patients, when all four PVs were isolated.

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Objective: The purpose of this study was to provide detailed information as to the modification of electrophysiological properties of pulmonary veins (PVs) and adjacent left atrial (LA) tissue caused by circumferential ablation (ABL) of superior and inferior pulmonary vein ostia using a novel radio-frequency balloon catheter (RBC), and to correlate such changes with recurrence or non-recurrence of atrial fibrillation (AF).
Background: Although isolation of the triggering foci in PVs using conventional ABL techniques is useful in the treatment of AF, ABL of PVs per se is time consuming and tends to be associated with high AF recurrence rate.
Methods and Results: Forty-nine patients with AF refractory to antiarrhythmic medication underwent circumferential ablation of PV-LA junction by RBC. Post ablation changes in electrophysiological properties around the PV ostia were studied with a basket catheter and were correlated with AF recurrence in 34 (1^st study) early cases (ablating 68 superior PVs) and 15 (2^nd study) later cases (53 superior and inferior PVs). Total elimination of PV potentials or PV-LA dissociation was achieved in 93% (63/68 PVs) and 93% (49/53 PVs), respectively. During mean follow-up periods of 24.1±4.1 and 13.3±1.7 months, AF recurred in 38% (13/34 cases) and 13% (2/15) in early and later groups, respectively, but no case developed severe PV stenosis. Although the amplitude of PV and periostial LA potentials were decreased (p<0.0001) in all patients, the remaining PV potentials in 34 non-recurrence cases were definitely smaller than those in 15 recurrence cases (p<0.0001). When a cut-off level of less than 0.4 mV in receiver operating characteristic curves was used, its negative predictive value for non-recurrence of AF was 93% and specificity was 95%.
Conclusions: Circumferential ablation around the PV ostia using the RBC is effective in the treatment of AF even in a single session, and AF recurrence may well be predicted by precisely measuring the amplitude of remaining PV-LA potentials.

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Pulmonary veins (PVs) have been shown to play an important role in the induction and perpetuation of focal AF. Fifty-one patients with AF, and 24 patients without AF as control subjects, were enrolled in this study. Signal-averaged P-wave recording was performed, and the filtered P wave duration (FPD), the root-mean-square voltage for the last 20, 30 and 40 ms (RMS20, 30, and 40, respectively) were compared. In 7 patients with AF, these parameters were compared before and after the catheter ablation. The FPD was significantly longer and the RMS20 was smaller in the patients with AF than those without AF. Because RMS30 was widely distributed between 2 and 10 μV, the AF group was sub-divided into two groups; Group 1 was comprised of the patients with an RMS30 ≥5.0 μV, and group 2, <5.0 μV. In group 1, short-coupled PACs were more frequently documented on Holter monitoring, and exercise testing more readily induced AF. After successful electrical disconnection between the LA and PVs, each micropotential parameter was significantly attenuated. These results indicate that the high frequency signal amplitude of the last component of the P wave is relatively high in patients with AF triggered by focal repetitive excitations most likely originating from the PVs. That is, attenuation by the LA-PV electrical isolation, and thus the high frequency P signals of the last component, may contain the electrical excitation of the PV musculature.

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Non-invasive recording of the late potential (LP) by signal-averaging technique is useful in predicting ventricular tachycardia (VT), especially in patients with myocardial infarction (MI). However, the rate of positive LP is much lower in anterior or anteroseptal MI than inferior MI since the LP is sometimes masked by QRS complex. The purpose of the present study is firstly, to detect local conduction delay in initial portion of QRS complex and secondarily, to evaluate the clinical significance of the initial delay in patients with MI. Eighty patients with MI were analyzed in 4 groups as follows: AS: anteroseptal, n=18, including 6 VT; A: anterior, n=22, 7 VT; I: inferior, n=28, 9 VT; and P: posterior, n=12, noVT. Twenty non-MI patients were used as normal controls (N). A signal processor (NEC 7T 18) was used to record signal-averaged electrocardiograms and each 10 msec integral value of filtered QRS complex from the initial upstroke to the 60 msec point was automatically measured.
The integral values of groups AS and A were lower than those of groups I, P, and N. AS patients with VT showed a lower integral value than AS patients without VT, but no differences were observed between A patients with VT and A patients without VT.
We conclude that there is a much more sluggish upstroke in the signal-averaged initial QRS complex in anteroseptal MI patients with VT, suggesting that the local conduction delay at the ventricular septum plays an important role in the mechanism of VT in these patients.

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Right bundle branch block (RBBB) pattern recorded during right ventricular (RV) endocardial pacing should be given special attention in terms of safe RV pacing or lead malposition, e.g. left ventricular pacing or coronary venous pacing, even for patients with no symptoms. Paced electrocardiograms from 47 consecutive patients with a pacemaker implanted were studied. Four patients (8.5%) were found to have RBBB pattern recorded in precordial V₁ and V₂ leads in the usual 4^th intercostal space. All of these patients showed left bundle branch block (LBBB) pattern in limb leads. When precordial V₁ and V₂ leads in the 5^th space were recorded, RBBB pattern changed to LBBB pattern. Biplane chest X-ray film and echocardiogram, especially 3D echo mode, confirmed that tips of pacing leads of the 4 patients were located in the distal RV septum or the apex. RBBB pattern observed during RV endocardial pacing usually represents safe RV endocardial pacing rather than perforation or malposition of pacing leads.

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A 72-year-old man with a thin build had an ICD system with a generator implanted at left prepectoral space. The generator was exposed through thin overlying skin at 11 months following surgery. Although it was undermined with the adjacent skin, it was exposed again 6 months later. The generator was replaced in the ipsilateral subpectoral space. Since then, no signs of recurrence have been observed for the subsequent 12 months, with the patient pleased with its cosmetic appearance. This case illustrates the benefits of subpectoral implantation in the current ICD era in which subcutaneous implantation is common.

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We studied the modes of initiation of two types of atrial reentrant tachycardias (i.e., micro-reentry isthmus tachycardia and counterclockwise atrial flutter) in a 39-year-old male with typical atrial flutter. Rapid atrial pacing from proximal coronary sinus at a cycle length of 220 msec initiated micro-reentry isthmus tachycardia (non-sustained), while rapid atrial pacing at a cycle length of 210 msec initiated sustained atrial flutter circulating counterclockwise around the tricuspid annulus. It was suggested that initiation of the counterclockwise atrial flutter was associated with a pacing-induced conduction block in the entire width of the isthmus, whereas initiation of the micro-reentry isthmus tachycardia was associated with a pacing-induced conduction block in a limited segment of the isthmus (i.e., partial isthmus block).

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